MVTL Laboratories: Nutrient Analysis Guide New Ulm, MN Nevada, IA Bismarck, ND Glossary Primary Nutrients Nitrogen (N) Phosphorus (P) Potassium (K) Secondary Nutrients Sulfur (S) Calcium (Ca) Magnesium (Mg) Micro Nutrients Zinc (Zn) Iron (Fe) Manganese (Mn) Copper (Cu) Boron (B) Chloride (Cl) Molybdenum (Mo) Micro Nutrient Sensitivity Soil pH and Buffer pH Organic Matter Soluble Salts Exchangeable Sodium CEC (Cation Exchange Capacity) % Base Saturation SAR (Sodium Absorption Ratio) Texture CCE (Calcium Carbonate Equivalent) Primary Nutrients Nitrogen – (N) Nitrogen Role in Plant Growth 
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Essential in formation of Amino Acids – the building blocks of protein Part of DNA molecule – responsible for cell division and reproduction and plant growth Part of Chlorophyll molecule (the light receptor of plants – turns light energy into plant energy) Aids in production and usage of carbohydrates Affects energy reaction in plants and is a key component of vitamins Nitrogen in Soils  Nitrogen in soils can be supplied by: o Commercial Fertilizer, Atmospheric, Organic Matter, Crop Residues, Animal Manures  Nitrogen Loss in Soils o Nitrification  Nitrification is a biological process where bacteria transform NH4 into NO3. Proceeds rapidly under warm, moist and well aerated soil conditions  Ammonium (NH4) is stable in soil until nitrification occurs (NH4 ‐> NO3) o Denitrification  Bacteria convert NO3 to N gases and lost to the atmosphere under saturated soils (anaerobic conditions). Some anaerobic bacteria in water logged soils get oxygen from NO3 to produce N2 which is then released to the atmosphere. o Leaching  Nitrate (NO3) – water soluble and prone to movement  Nitrate loss down the soil structure with water o Volatilization  Occurs when Ammonia (NH3) isn’t converted to Ammonium (NH4) lost to the atmosphere as a gas.  Volatilization can occur during  Unincorporated nitrogen fertilizers into soil surface  High soil temperatures, warm and windy weather  Moist, drying soil conditions Nitrogen Deficiency Symptoms Nitrogen is mobile in plants, meaning it can move to areas where the nutrient is needed. In plants, nitrogen deficiencies first show up on the oldest plant tissues first. Symptoms advance up the plant to younger leaves. In Corn, nitrogen deficient plants are spindly, pale and stunted. Lower leaves develop a yellow‐orange color in the shape of an inverted “V” beginning at the tip and following the midvein. Leaves may begin to die (fire) at the tip. Ears are small and pinched at the tip. Symptoms are favored by cold, ponded, dry or low organic matter soil and incorporation of low‐nitrogen residues. Nitrogen Soil Testing Procedure ‐ Nitrate‐Nitrogen (Cadmium Reduction Method) Nitrate‐Nitrogen is determined using the Cadmium Reduction Method, which reduces NO3 to NO2. This reduction forms colored compounds which the intensity is measured by a spectrometer. Most calibrations for Nitrate‐Nitrogen are based on sampling depth, geographic location, and time of year. Fertilizer nitrogen is just one of the nitrogen sources that plants utilize. Another common source is released by the mineralization of organic matter, therefore, requires proper evaluation. The relative level of nitrate‐nitrogen is variable and depends on the season, yield goal, and level of OM. Concentrations In general, less than 0‐30 lbs at 24” depth is considered low, while 30‐60 lbs is medium, and 60+ lbs is high. Primary Nutrients Phosphorus – (P) Phosphorus Role in Plant Growth 
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Part of ATP Molecule which circulates energy through the plant Part of Organic compounds found in plants Stores and transfers energy to drive reactions within cells that promote photosynthesis and respiration Enhances dell division/enlargement Promotes root formation, early plant growth, and hastens maturity Improves hardiness, seed quality, and disease resistance Phosphorus in Soils Phosphorus exists in soil as both an organic form and inorganic forms. Organic forms are found humus or other organic materials. Through the process of mineralization by microorganisms, organic phosphorus is released into a soluble form from the breakdown of organic matter for plant growth. Soil temperature and moisture have an effect how much mineralization takes place. In general, the most mineralization takes place when soils are warm and well drained. Inorganic phosphorous occurs when phosphorus combines with iron (Fe), aluminum (Al) and calcium (Ca). The phosphorus reacts with those elements to produce a form of phosphorous that is not very soluble, or “fixed” or “tied‐up” by the soil. The solubility of the various inorganic phosphorous compounds had a direct impact on the availability of phosphorous for crop growth. Phosphorous solubility is related to soil pH. In very low pH’s (less than 5.0), iron and aluminum fix phosphorous availability. With a pH of 7.3 or above, fixation of phosphorous by calcium is a concern. Phosphorous that is fixed is not measured by routine soil test procedures. Phosphorous Deficiency Symptoms In corn, leaves of young phosphorus‐deficient plants are bluish‐green and slightly narrowed, turning reddish‐purple starting at the tips and along the edges. Leaf tips may die. If conditions for phosphorous uptake improve, newer leaves may by symptom‐free. Symptoms are seldom observed on knee‐high and larger plants. Ears may be small and misshapen, twisted with one or more kernel rows missing on one side. In soybeans, phosphorous deficiencies generally appear as thin and dwarfed stems, lack‐luster or blue‐green upward pointing leaves, and general early defoliation. Leaves tend to be more erect and form an acute angle with the stem. A limited supply of phosphorus reduces the number, as well as the efficiency, of nodulating bacteria. Phosphorus deficiency is easily diagnosed through soil testing, but difficult to correct within the crop year. Phosphorous Soil Test Procedures – (Colorimeter) There are three different extractions used by MVTL to determine levels of available P. Olsen‐
Bicarbonate is generally used where soil pH is at or above 7.2. This method has a known reliability in alkaline soils with medium to high CEC levels, as well as, free lime or calcareous soils. Bray I is best adapted to fine‐textured soils where the pH levels are well below 7.0. Bray I methods typically do not perform well in high lime soils and/or higher CEC’s. The Mehlich III method is used in much of Iowa. It has proven to be a more stable method versus Bray, because it can adjust to excess (free) lime and a larger pH scale. Mehlich III, like Bray I, use the same fertility scale to differentiate between high and very high testing soils. In all three testing methods, P is extracted from the soil; a developing agent is added to the extract to change the color and the intensity is read by the colorimeter. Concentrations Bray & Mehlich – V. Low (0‐5ppm) Low (6‐10ppm) Medium (11‐15ppm) High (16‐20ppm) V. High (21+) Olsen – V. Low (0‐3ppm) Low (4‐7ppm) Medium (8‐11ppm) High (12‐15ppm) V. High (16+) Soil Recommendations are given according to crop removals, but economics and farming practices by individual producers should be examined when making further recommendations. A maintenance recommendation should be considered for soils testing High to Very High (16+ppm). Soils testing very low to low (<11ppm) will have the greatest benefit and return from build recommendations. In most cases, soils testing Very High (>21ppm) will not benefit from additional phosphorus fertilizer. Primary Nutrients Potassium – (K) Potassium Role in Plant Growth 
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Associated with the movement of water, nutrients and carbohydrates in plant tissue Stimulates early growth Enhancing protein production Improves seed quality, plant hardiness, and disease resistance Potassium in Soils In general, huge quantities of potassium are found in soil. Most all of it is found in the structural component of the soil minerals and is not available for plant growth. Due to differences in parent materials and the effect of weathering rates on soil, the amount of potassium the soil generates for plant growth varies and often the need to supply potassium as a fertilizer is warranted for crop production. Three forms of potassium exist in soils: Unavailable K, Slowly Available K, and Readily Available K. 
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Unavailable K 90‐98% of K found in soil is unavailable for plant uptake. Most of this is found in feldspars and micas, which are crystalline forms of K which plants aren’t able to use. Over a long period of time, the weathering process breaks down the crystals and the K is released to a slowly available form. This process is slow and cannot supply the full needs of field crops Slowly Available K This form of K is thought to be trapped or fixed between layers of clay minerals. It is unavailable for plant uptake. While some slowly available K is released during the growing season, some readily available K can fixed between layers of clay to be converted to slowly available K. The amount of K that can be fixed varies with the types of clay across the landscape. In areas where Montmorillonite clays dominate (central, western Minnesota), these soils fix K when soils become dry by trapping it between layers of clay minerals. They also release K when soil becomes wet. Readily Available K Potassium that is water soluble, or dissolved in soil water and held on the exchange sites of clay particles (exchangeable K) is considered readily available for plant growth. This is the form of K that routine soil test measure. Potassium Deficiency Symptoms In plants, K is mobile and will move from the lower leaves to the upper leaves. For Corn, symptoms first show up in the lower leaves with the leaf margins turning brown and the remainder of the leaf has a lighter green, striped appearance. The striping appearance can also be confused with sulfur, magnesium and zinc deficiencies. In soybeans, the margins of the leaf turn a lighter shade of green or yellow, again on the lower leaves. Potassium Soil Testing Procedures – Atomic Absorption Potassium is extracted from the soil using an ammonium acetate solution. The concentration is then obtained by analyzing the extracting solution using an AA (atomic absorption) spectrophotometer. This amount is considered readily available or exchangeable potassium. The potassium supplying power of the soil is determined by the exchangeable (readily available). The amount or percent of exchangeable potassium needs to be higher on sandy soils (lower CEC’s), but on clay soils (higher CEC’s) it can be lower and still supply the plants with enough potassium. Concentrations Very Low (0‐40ppm) Low (41‐80ppm) Medium (81‐120ppm) High (121‐160ppm) Very High (161+) Soil Recommendations are given according to crop removals, but economics and farming practices by individual producers should be examined when making further recommendations. Soils testing below 100ppm will benefit the most from potassium fertilizers. For soils testing over 200ppm, adding potassium fertilizer may not be beneficial Secondary Nutrients Sulfur – (S) Sulfur Role in Plant Growth 
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Integral part in the formation of Amino Acids Helps to develop enzymes and vitamins Promoter of nodule formations on legumes Aids seed production Necessary for chlorophyll formation Sulfur in Soils The majority of sulfur in soil is supplied by organic matter, while smaller amounts of sulfur are supplied by soil minerals, atmosphere and fertilizers. Sulfur is generally removed from the soil by two ways, either through crop removal and/or is mobile and affected by leaching down the soil surface, much like nitrate. Sulfur Deficiency Symptoms When S is deficient, growth is reduced and maturity is delayed. Also, inadequate supplies of S can cause a reduction in protein formation with that will allow foliage to yellow. In corn, deficiencies of S causes stunted, slow‐growing and yellow plants. Yellowing occurs between veins, especially of younger (upper) leaves. Older plants rarely show symptoms. Symptoms are favored by cold, wet soil, low pH and low organic matter. In alfalfa and clover, the entire leaf area has a light green color. Sulfur Soil Testing Procedures ‐ Colorimeter, FIA Extractable sulfur is reported in ppm of sulfate‐sulfur. The determination is made on a 0‐6” or 0‐24” sample. Concentrations V. Low (0‐3ppm) Low (4‐7ppm) Medium (7‐11ppm) High (11‐15ppm) V. High (15+) Optimum levels of S depend largely on organic matter content, soil texture, drainage and yield goals. Sulfur deficiency has generally been limited to soils low in organic matter, since organic matter is the primary source of sulfur in soils. Secondary Nutrients Calcium – (Ca) Calcium Role in Plant Growth 
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Strengthen cell walls and structure Helps prevent disease Increases plant metabolism – promotes early root growth and formation Improves soil acidity Calcium in Soils Calcium is present in adequate amounts in most soils. Calcium is a component of several primary and secondary minerals in the soil, which are essentially insoluble for agricultural considerations. These materials are the original sources of the soluble or available forms of Ca. Calcium is also present in relatively soluble forms, as a cation (positively charged Ca++) adsorbed to the soil colloidal complex. The ionic form is considered to be available to crops. Calcium is found in many of the primary or secondary minerals in the soil. In this state it is relatively insoluble. Calcium is not considered a leachable nutrient. However, over hundreds of years, it will move deeper into the soil. Because of this, and the fact that many soils are derived from limestone bedrock, many soils have higher levels of Ca, and a higher pH in the subsoil. 
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Soil pH: Acid soils have less Ca, and high pH soils normally have more. As the soil pH increases above pH 7.2, due to additional soil Ca, the additional "free" Ca is not adsorbed onto the soil. Much of the free Ca forms nearly insoluble compounds with other elements such as phosphorus (P), thus making P less available. Soil CEC: Lower CEC soils hold less Ca, and high CEC soils hold more. Cation competition: Abnormally high levels, or application rates of other cations, in the presence of low to moderate soil Ca levels tends to reduce the uptake of Ca. Alkaline sodic soil (high sodium content): Excess sodium (Na) in the soil competes with Ca, and other cations to reduce their availability to crops. Sub‐soil or parent material: Soils derived from limestone, marl, or other high Ca minerals will tend to have high Ca levels, while those derived from shale or sandstone will tend to have lower levels. Interactions Other cations: Being a major cation, calcium availability is related to the soil CEC, and it is in competition with other major cations such as sodium (Na+), potassium (K+), magnesium (Mg++), Ammonium (NH4+), iron (Fe++), and aluminum (Al+++) for uptake by the crop. High K applications have been known to reduce the Ca uptake in apples, which are extremely susceptible to poor Ca uptake and translocation within the tree. Sodium(Na+): High levels of soil Na will displace Ca and lead to Ca leaching. This can result in poor soil structure and possible Na toxicity to the crop. Conversely, applications of soluble Ca, typically as gypsum, are commonly used to desalinate sodic soils through the displacement principle in reverse. Phosphorus(P): As the soil pH is increased above pH 7.0, free or un‐combined Ca begins to accumulate in the soil. This Ca is available to interact with other nutrients. Soluble P is an anion, 
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meaning it has a negative charge. Any free Ca reacts with P to form insoluble (or very slowly soluble) Ca‐P compounds that are not readily available to plants. Since there is typically much more available Ca in the soil than P, this interaction nearly always results in less P availability. Iron(Fe++) and Aluminum(Al+++): As the pH of a soil decreases, more of these elements become soluble and combine with Ca to for essentially insoluble compounds. Boron(B‐): High soil or plant Calcium levels can inhibit B uptake and utilization. Calcium sprays and soil applications have been effectively used to help detoxify B over‐applications. Calcium Deficiency Symptoms Calcium deficiency symptoms can be rather vague since the situation often is accompanied by a low soil pH. Visible deficiency symptoms are seldom seen in agronomic crops but will typically include a failure of the new growth to develop properly. Annual grasses such as corn will have deformed emerging leaves that fail to unroll from the whorl. The new leaves are often chlorotic. Extremely acid soils can introduce an entirely new set of symptoms, often from different toxicity's and deficiencies. Calcium Soil Testing Procedures – Atomic Absorption Calcium is extracted from the soils using ammonium acetate solution and reported in ppm. Knowing the amount of exchangeable Ca is an important for the calculation of the Cation Exchange Capacity (CEC) by summation. Ca deficiencies are most likely in coarse textured soils with pH less than 6.0. Concentrations Very Low (0‐250ppm) Low (251‐500) Medium (501‐2000) High (2000‐4500) Very High (4500+) Secondary Nutrients Magnesium – (Mg) Magnesium Role in Plant Growth 
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Key element in chlorophyll production Improves efficiency and mobility of phosphorus and iron Activates enzymes Magnesium in Soils Magnesium is a component of several primary and secondary minerals in the soil, which are essentially insoluble, for agricultural considerations. These materials are the original sources of the soluble or available forms of Mg. Magnesium is also present in relatively soluble forms, and is found in ionic form (Mg++) adhered to the soil colloidal complex. The ionic form is considered to be available to crops. Factors Affecting Availability 
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Soil Mg content: Soils inherently low or high in Mg containing minerals. Soil pH: Low soil pH decreases Mg availability, and high soil pH increases availability Soil Mg:Mn ratio: High available Mn can directly reduce Mg uptake. This may be independent of the acid conditions normally associated with excess available Mn in the soil. Soil CEC: Low CEC soils hold less Mg, while high CEC soils can hold abundant Mg. However, if a high CEC soil does not happen to have strong levels of Mg, it will tend to release less of the Mg that it holds to the crop. Cation competition: Soil with high levels of K or Ca will typically provide less Mg to the crop High cation applications: High application rates of other cations, especially K, can reduce the uptake of Mg. This is most common on grasses, and corn seems to be the most sensitive grass. Low soil temperatures Interactions Other cations: Being a major cation, Mg availability is related to the soil CEC, and it is in competition with other major cations such as calcium (Ca++), potassium (K+), sodium (Na+), ammonium (NH4+), iron (Fe++), and aluminum (Al+++). Phosphorus: Phosphorus uptake is often enhanced when applied with Mg fertilizers. However, mixing some liquid or suspension sources of P and Mg can lead to a reaction can result in the formation of a large amount of precipitated material, to the point of near solidification of the mixture. Sulfur: Sulfur leaching is often increased where supplemental Magnesium is applied Magnesium Deficiency Symptoms The classic deficiency symptom is interveinal chlorosis of the lower/older leaves. However, the first symptom is generally a more pale green color that may be more pronounced in the lower/older leaves. In some plants, the leaf margins will curve upward or turn a red‐brown to purple in color. Full season symptoms include preharvest leaf drop, weakened stalks, and long branched roots. Calcium Soil Testing Prodecures – Atomic Absorption Magnesium is extracted from the soils using ammonium acetate solution and reported in ppm. Knowing the amount of exchangeable Mg is important for the calculation of the Cation Exchange Capacity (CEC) by summation. Mg deficiencies are most likely in coarse textured soils with pH less than 6.0. Toxicity Magnesium toxicity's are rare. Crops grown on heavy Montmorillonite clay soils that have been poorly fertilized with potassium may exhibit excesses of magnesium in their tissue. But, before the tissue level approaches toxicity, potassium deficiency will occur. Higher tissue levels of magnesium are usually found in the older leaves on the plant and may be associated with diseased or damaged leaves. Concentrations Low (0‐50ppm) Medium (51‐100ppm) High(100+) High Soil testing is the first step in determining a need. If the analysis shows a need and a supplemental application is indicated, you can be confident the application will be economically sound. As always Plant Analyses are also useful in uncovering “hidden”; Magnesium shortages and when a need is determined, treatment should follow. Magnesium is a constituent of most agricultural lime, as well as specific Mg fertilizers. Magnesium containing materials applied to the soil may serve two functions. Correcting problems is often difficult. Proper liming with dolomitic limestone is almost always the most practical solution to low Mg, even if the dolomite is more expensive. Supplemental broadcast and row applications will most likely need to be repeated over a period of several years. If row applied fertilizers are used where magnesium shortage is a problem, it is desirable to minimize in‐row K applications to avoid K‐Mg competition. However, materials such as Sul‐Po‐Mag and K‐Mag that contain both nutrients have been used to partially satisfy Mg needs on soils where the crops had significant Mg stress caused by extremely high K levels. Micro‐Nutrients Zinc – (Zn) Zinc Role in Plant Growth 
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Vital to enzyme system Allows plant to efficiently metabolize other crop nutrients Necessary for chlorophyll production, carbohydrate and starch formation Aids in seed formation Zinc Deficiency Symptoms Plants fail to develop normally in soils that are deficient of Zn. In corn, symptoms of Zn deficiency are rare beyond the seedling stage. Yellow to white bleached bands appear on the lower part of leaves while the midvein, margins and tip remain green. The deficiency is favored by high soil phosphorus, high pH, cool, wet soil and low organic matter. Also, lack of normal elongation between internodes of corn is a common symptom. Concentrations Very Low (0‐.25ppm) Low (.26‐.50ppm) Medium (.51‐.75ppm) High (.76‐1.0ppm) Very High (1.01+ppm) Zinc Soil Test Procedures – Atomic Absorption Zinc is extracted using a DPTA solution and reported in ppm. Soil test levels greater than 1.0 ppm are considered adequate for all crops. Levels between 0.5 and 1.0 ppm are marginal, and less than 0.5 ppm is considered low. Corn, edible beans, flax, and potatoes are more responsive to zinc than most crops. Zinc deficiencies are most likely as soil pH increases. Also, soils with low organic matter will increase the chances of crops being sensitive to zinc and other micro deficiencies. Need for Zinc Fertilizers Under these conditions, a response to Zn fertilizer might be expected 
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Soil Temperature. Cool soil temperatures in early spring can intensify the need for Zn. When soils are cold, the organic matter does not decompose and Zn is not released and available for crop growth. Soil Texture. Most of the response to Zn in a fertilizer program will take place on fine‐textured soils. Recent research on sandy soils indicates a response to Zn can occur when high yields are grown on sandy soils with a low organic matter content. The measured response to Zn 
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fertilization in these situations has been small and has not occurred every year. Use the zinc soil test to determine if Zn is needed in a fertilizer program. Topsoil Removal. The probability of a response to Zn fertilization increases where topsoil has been removed or eroded away. When soils are eroded, the amount of free calcium carbonate on the soil surface increases. The probability of the need for Zn in a fertilizer program increases as the percentage of free calcium carbonate increases. Previous Crop. The probability of a response to Zn fertilization increases if either corn or dry edible beans follows a crop of sugar beets. Phosphorus Levels. There is a known relationship between phosphorus (P) and Zn in soils. Excessive applications of phosphate fertilizers have caused a Zn deficiency in corn and reduced yields. The P‐induced Zn deficiency might be a concern when high rates of manure are applied to crop land. The manure, however, also contains Zn that can be used for crop growth. Therefore, P supplied from manure should not create a Zn deficiency for crop production in Minnesota. Micro Nutrients Iron – (Fe) Iron Role in Plant Growth 
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Promotes formation of chlorophyll Used in reactions involving cell division and growth Acts as the plants oxygen carrier. Factor affecting availability 
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Soil pH: High soil pH reduces Fe availability while acid soils increase Fe availability. The high pH effect is increased in waterlogged, compacted, or other poorly aerated soils. One factor in this effect is the presence of high carbonates in the soil, which also plays a role in waterlogged soils and in the root rhizosphere reaction to certain other nutrients and fertilizer sources. Low Organic Matter: In addition to being a source of Fe, O.M. compounds are able to form Fe complexes that improve availability. Saturated, Compacted, or Other Poorly Aerated Soils: In acid soils, this condition can increase Fe availability (to the point of toxicity). High Soil P: Excessive amounts of soluble P, or high rates of P fertilizer, have been demonstrated to inhibit Fe uptake in many crops. HCO3‐ : Iron deficiency can be induced by the presence of the bicarbonate ion in the soil (saline and alkali conditions). Iron Deficiency Symptoms Interveinal chlorosis of young leaves. Severe deficiencies may progressively affect the entire plant turning the leaves from yellow to bleached‐white. Luckily, most agricultural soils provide an abundant supply of Fe to plants, because iron can be more difficult to use in a fertility program than other nutrients. Most soil application methods are often not very effective, while the needed multiple foliar applications are often too expensive, or labor intensive.
Iron Soil Testing Procedures – Atomic Absorption These levels are determined using DPTA extraction and reported in ppm. Soils with test levels greater than 4.0 ppm (Fe) are unlikely to show a response to nutrient applications. Concentrations Very Low (0‐2.5ppm) Low (2.6‐5.0ppm) Medium (5.1‐7.5ppm) High (7.6‐10.0) Very High (10.0+) Micro Nutrients Manganese – (Mn) Manganese Role in Plant Growth 
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Aids enzymes and chlorophyll productions Increases the availability of phosphorous Factors affecting availability 
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Soil pH: High soil pH reduces Mn availability while low soil pH will increase availability, even to the point of toxicity. Organic Matter: Mn can be “tied up” by the organic matter such that high organic matter soils can be Mn deficient. Soil Moisture: Under short‐term waterlogged conditions, plant available Mn++ can be reduced to Mn+, which is unavailable to plants. Manganese Deficiency Symptoms Because Mn is not translocated in the plant, deficiency symptoms appear first on younger leaves. The most common symptoms on most plants are interveinal chlorosis. Sometimes a series of brownish‐black specks appear in the affected areas. In small grains, grayish areas appear near the base of younger leaves. Manganese deficiencies occur most often on soils with a high pH and/or naturally low Mn content. Toxicity Manganese toxicity is a relatively common problem compared to other micronutrient toxicity. It normally is associated with soils of pH 5.5 or lower, but can occur whenever the soil pH is below 6.0. Symptoms include chlorosis and necrotic lesions on old leaves and dark‐brown or red necrotic spots Manganese Soil Testing Procedures – Atomic Absorption These levels are determined using DPTA extraction and reported in ppm. Soils with test levels greater than 1.0 ppm (Mn) are unlikely to show a response to nutrient applications. Concentrations Very Low (0‐1.0ppm) Low (1.1‐2.0ppm) Medium (2.1‐3.0ppm) High (3.1‐4.0) Very High (4.1s+) Micro Nutrients Copper – (Cu) Copper Role in Plant Growth 
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Involved in Chlorophyll formation and photosynthesis Needed for energy transfer in plants Promotes seed production and formation Copper in Soils The amount of Cu available to plants varies widely by soils. Available Cu can vary from 1 to 200 ppm in both mineral and organic soils as a function of soil pH and soil texture. The finer‐textured mineral soils generally contain the highest amounts of Cu. The lowest concentrations are associated with the organic or peat soils. Availability of Cu is related to soil pH. As soil pH increases, the availability of this nutrient decreases. Copper is not mobile in soils. It is attracted to soil organic matter and clay minerals. Copper Deficiency Symptoms Symptoms of Cu deficiency appear when small grains are grown on organic soils. Symptoms of Cu deficiency are almost never seen in corn/soybean production fields. These deficiency symptoms are characterized by a general light green to yellow color in the small grain crop. The leaf tips die back and the tips are twisted. A typical deficiency symptom for wheat is shown in the photographs. Cu deficiency is severe enough, growth of small grains ceases and plants die after reaching the tillering growth stage. Wheat will not have grain in the head. Deficiency symptoms have only been observed when small grains are grown on peat soils. Foliar applications of Cu can be an effective way to correct Cu deficiencies in small grains. Soil applications of Cu last for many years. Copper becomes attached to the soil organic matter and is not moved through the soil by water. Leaching is prevented, but the Cu is still available to plants. If the soil test for Cu is in the high range, annual applications of Cu are not needed. Since large amounts of Cu in soils can be toxic to plants, it is important to accurately control applications. To avoid toxicity problems, annual applications of Cu should certainly be less than 40 lb. per acre. Toxicity problems are difficult to correct Cooper Soil Test Procedures – Atomic Absorption These levels are determined using DPTA extraction and reported in ppm. Soils with test levels greater than 0.2 ppm are unlikely to show a response to nutrient applications. Concentrations – Very Low (.1‐.2ppm) Low ( .3‐.4ppm) Medium (.5‐.6ppm) High (.7‐.8) Very High (.8+) Micro Nutrients Boron – (B) Boron Role in Plant Growth 
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Essential for seed and cell wall formation Necessary for sugar translocation Enhances plant maturity Boron in Soils Most soils are capable of supplying adequate amounts of boron for crop production. Research has shown, however, that using boron fertilizers will improve the yield of alfalfa and vegetables on some sandy soils. Where needed, use of boron can be profitable. A response to boron use might be expected on soils that have a sandy loam, loamy sand, or sand texture with low organic matter content. Most of the boron in soils is contained in the organic matter. As decomposition of organic matter takes place, boron is released for plant growth. Breakdown of organic matter is nearly stopped during dry weather. Boron Deficiency Symptoms Boron is not mobile in plants so deficiency symptoms will occur as stunting on the upper part of plants. With alfalfa, stunting of the new growth gives the plant a bushy, umbrella‐like appearance. The lower (older) leaves stay green. Severely affected plants do not produce blossoms; an extensive yield loss occurs; and plants winterkill easily. When the deficiency is severe in alfalfa, the growing point dies. Boron Soil Test Procedures ‐ Colorimeter A boron level is determined by using acid extracts and hot water to release boron from the soil and is reported in ppm. Many factors affect boron availability to plants. These include organic matter, soil texture, and soil pH. Crops like alfalfa, and many vegetable crops, tend to show the most response to added boron on deficient soils. Soils testing less than 1 ppm will likely be deficient, but following up with a plant analysis is recommended. Levels in excess of 4‐5.0 ppm may be toxic to some crops. Concentrations – V. Low (0‐.4ppm) Low (.5‐.8ppm) Medium (.9‐1.2ppm) High (1.3‐1.6) V. High (1.6+) Chloride ‐ Cl Chloride role in plant growth 
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It is essential (working in tandem with K+) to the proper function of the plants stomatal openings, thus controlling internal water balance. It also functions in photosynthesis, specifically the water splitting system. It functions in cation balance and transport within the plant. Research has demonstrated that Cl diminishes the effects of fungal infections in an, as yet undefined, way. It is speculated that Cl competes with nitrate uptake tending to promote the use of ammonium N. This may be a factor in its role in disease suppression, since high plant nitrates have been associated with disease severity Factors affecting availability Most soil Cl is highly soluble and is found predominantly dissolved in the soil water. Chloride is found in the soil as the Chloride anion. Being an anion it is fully mobile except where held by soil anion exchange sites (Kaolinite clays, Iron and Aluminum Oxides). In areas where rainfall is relatively high and internal soil drainage is good, it may be leached from the soil profile. Also, where muriate of potash fertilizer is not regularly applied Chloride deficiencies can occur. Atmospheric Chloride deposition tends to be rather high along coastal regions and decreases as you progress inland. Chloride, nitrate, sulfate, boron, and molybdenum are all anions in their available forms, and in that form they are antagonistic to each other. Therefore, an excess of one can decrease the availability of another. Chloride Deficiency Symptoms Wilting, restricted and highly branched root system, often with stubby tips. Leaf mottling and leaflet blade tip wilting with chlorosis has also been observed. Molybdenum – (Mo) Molybdenum Role in Plant Growth 
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It functions in converting nitrates (NO3 ) into amino acids within the plant. It is essential to the symbiotic nitrogen fixing bacteria in legumes. It is essential to the conversion of inorganic P into organic forms in the plant. Molybdenum Deficiency Symptoms Molybdenum deficiency is rare. Young leaves sometimes twist, wilt and die along margins. Older leaves die at tips, along margins and between veins. Deficiency is favor by low pH and strong soil weathering Micro‐nutrient Sensitivity of Major Crops Nutrient Sensitive Crops Soil Conditions Likely Zinc Corn Soil Test < 1.5 ppm Edible Beans High pH, Low O.M. Potatoes Cool and wet soils Boron Alfalfa Soil Test < 1.0 ppm Sugar Beets High pH, Low O.M. Copper Wheat Soil Test < 0.3 ppm Barley High O.M. Iron Beans Soil Test < 4.0 ppm Millet High pH Sorghum High carbonates Manganese Navy Beans Soil Test < 2.0 ppm Soybeans & Oats Molybdenum Alfalfa Soil Test < 0.1 ppm High pH Chloride Wheat Oats Barley Soil Test < 7.0 ppm per depth Dryland soils testing High in potassium (K) Peas High pH Soil pH and Buffer pH Soil pH This is a measure of the soil acidity or alkalinity and is sometimes called the soil “water” pH. This is because it is a measure of the pH of the soil solution, which is considered the active pH that affects plant growth. Soil pH is the foundation of essentially all soil chemistry and nutrient reaction and should be the first consideration when evaluating a soil test. The total range of the soil pH scale is from 0‐14. Values below the mid‐point (pH 7.0) are acidic and those above pH 7.0 are alkaline. A soil pH of 7.0 is considered to be neutral. Most plants perform best in a soil that is slightly acid to neutral (pH 6.0‐7.0). Some plants like blueberries require the soil to be more acid (pH 4.5‐5.5), and other, like alfalfa will tolerate a slightly alkaline soil (pH 7.0‐7.5). The soil pH scale is logarithmic; meaning that each whole number is a factor of 10 larger or smaller than the ones next to it. For example if a soil has a pH of 7.0 and this pH is lowered to pH 6.0, the acid content of that soil is increased 10‐fold. If the pH is lowered further to pH 5.0, the acid content becomes 100 times greater than at pH 7.0. The logarithmic nature of the pH scale means that small changes in a soil pH can have large effects on nutrient availability and plant growth. Buffer pH This is a value that is generated in the laboratory, it is not an existing feature of the soil. Laboratories perform this test in order to develop lime recommendations, and it actually has no other practical value. In basic terms, the BpH is the resulting sample pH after the laboratory has added a liming material. In this test, the laboratory adds a chemical mixture called a buffering solution. This solution functions like extremely fast‐acting lime. Each soil sample receives the same amount of buffering solution; therefore the resulting pH is different for each sample. Too determine a lime recommendation, the laboratory looks at the difference between the original soil pH and the ending pH after the buffering solution has reacted with the soil. If the difference between the two pH measurements is large, it means that the soil pH is easily changed, and a low rate of lime will be sufficient. If the soil pH changes only a little after the buffering solution has reacted, it means that the soil pH is difficult to change and a larger lime addition is needed to reach the desired pH for the crop. Nutrient Availability with Different pH’s Organic Matter Percent OM is determined by the dry combustion method. OM content in soil is, especially, important for determining nitrogen and sulfur needs. The OM% along with soil texture can be very important when determining rates of certain soil‐applied herbicides. Soluble Salts Soluble salts in the soil are measured on a 1:1 soil:water suspension or using a saturated paste method (SPM). The amount of electrical current this suspension conducts is an indicator of the total salt content of the soil. A soil with a high soluble salt content will conduct more electricity than a soil with a low salt content. The relative amount of soluble salt in a soil is reported as millimhos per centimeter (mmhos/cm). High soluble salt levels can decrease water uptake of growing plants, therefore, affecting the growth and germination of many crops. Soluble salts are mobile. EC exceeding 0.50 mmhos/cm are damaging. See below: mmhos/cm 1:1 SPM 0‐.25 0‐2 .25‐.50 2‐4 .50‐1.0 4‐8 1.0‐1.5 8‐16 >1.5 >16 Poor Tolerance Soybeans Red Clover Green Beans Description Non‐Saline Slightly Saline Moderately Saline Strongly Saline Extremely Saline Effect on Crop None Sensitive Crop Restrictions Many Crop Restrictions Most Crops are Restricted Few Tolerant Crops Crop Tolerance Average Tolerance Wheat, Oats, Rye Corn, Sorghum Alfalfa, Sunflower Flax, many grasses Good Tolerance Barley Sugar Beets Rape Western Wheatgrass Exchangeable Sodium Sodium is extracted using ammonium acetate and is reported in ppm. Sodium is not a plant essential nutrient, but these levels are important for determining the CEC by summation. These levels also help establish excess amounts of sodium and whether they will have the potential to cause problems with soil structure. Concentrations: Very Low (0‐40ppm) Low (41‐80ppm) Medium (81‐120ppm) High (121‐160ppm) Very High (161+) Cation Exchange Capacity (CEC): CEC is routinely determined by the summation method. This method is more accurate for soils that do not contain free calcium and magnesium, generally, associated with soils with a pH of 7.0 or greater. When high levels of free calcium and magnesium are present, the CEC’s will appear higher and may provide inaccurate information for herbicide recommendations and other management decisions. Percent (%) Base Saturation: Percent base saturation is calculated from exchangeable potassium (K) 2‐7%, calcium (Ca) 65‐75%, magnesium (Mg) 10‐17%, and sodium (Na) 1‐5% when the CEC is reported by the summation method. Sodium can be damaging when it exceeds 2.5% (and/or is higher than the %K). SAR (Sodium Adsorption Ratio): The SAR reflects the Na:Ca + Mg. As sodium levels increase, the calcium and magnesium cations are replaced. This reduces soil structure and is often observed by crusting and low water permeability. An SAR ratio of 1‐5 is considered low and non‐damaging, 6‐10 is moderate and potentially damaging, and >11 is damaging. Other notes: High levels of sodium in the soil tend to flocculate (disperse soil particles), resulting in poor soil structure and low water infiltration. Since Sodium is mobile, added calcium (gypsum) will displace sodium and allow it to leach out of the soil profile by way of irrigation water and/or rainfall. Soils high in calcium have better structure than those high in sodium. Use of gypsum on soils where sodium is not high has generally not been shown to be effective in improving soil structure. Texture: Estimated texture is grouped into categories of coarse or medium/fine based on organic matter content. Peat is indicated if the organic matter level is greater than 20%. Precise texture determination can be made by measuring the percent sand, silt, and clay in the sample using the hydrometer method. Texture, along with organic matter content, is vital when determining rates for soil‐applied herbicides. Calcium Carbonate Equivalent (CCE): Measures the total calcium (Ca) & magnesium (Mg) in the soil. Levels 0‐2% carbonates is low, 2.5‐5% is medium, 5‐10% high, and >10% is considered very high. Testing your fields for carbonates when the pH is above 7.2 and the soluble salts are above 0.3 mmhos/cm will improve your ability to manage iron chlorosis. Soils with pH below 7.2 can also have considerable free Ca and Mg carbonates. In the table below, increase Risk Level when CCE’s are over 5%. ‐ Sandy soils with low organic matter (<3.0%) and a high salt level (>1.0) have a higher risk of iron chlorosis than a loam or clay soil with the same level of carbonates and salt. ‐ The risk and severity of iron chlorosis will increase in years with excessive moisture. ‐ When CCE’s are high, make sure the potassium (K) levels are in the very high range as well. CCE Soluble Salts Risk Level 1‐5% 0.3 – 0.4 Moderate 1‐5% 0.5 – 0.6 High 1‐5% 0.7 – 0.9 Very High 1‐5% 1.0 – 1.50 Extremely High 1‐5% > 1.50 Not Suitable (Soybeans) MVTL Fertilizer Cutoff Levels Analyte Guideline pH Organic Matter Salts Bray I – P Bray I – P Bray I – P Bray I – P Mehlich 3 ‐ P Mehlich 3 ‐ P Mehlich 3 ‐ P Mehlich 3 ‐ P Olsen – P Olsen – P Olsen – P Olsen – P Sulfur Boron Nitrate Potassium ‐ K Potassium ‐ K Potassium ‐ K Potassium ‐ K Mehlich 3 ‐ K Mehlich 3 ‐ K Mehlich 3 ‐ K Mehlich 3 ‐ K Calcium ‐ Ca Mehlich 3 ‐ Ca Magnesium ‐ Mg Mehlich 3 ‐ Mg Sodium ‐ Na Mehlich 3 ‐ Na Zinc Iron Copper Manganese Chloride BUILD BUILD BUILD IA IAWA TRI BUILD IA IAWA TRI BUILD IA IAWA TRI BUILD BUILD BUILD BUILD IA IAHSK TRI BUILD IA IAHSK TRI BUILD BUILD BUILD BUILD BUILD BUILD BUILD BUILD BUILD BUILD BUILD BUILD Cornstalk Nitrate(IA) ppm VL L M H VH 6.6 1.5 1 10 15 6 8 10 15 6 8 6 11 4 5 3 0.05 25 90 70 40 50 90 70 40 50 100 100 10 10 4 4 0.25 0.5 0.05 0.1 15 7.1 3 3 16 21 10 12 16 21 10 12 12 15 8 10 7 0.25 50 130 110 80 100 130 110 80 100 200 200 20 20 9 9 0.5 2.5 0.1 0.5 30 7.7 4.5 5 21 26 15 19 21 26 15 19 15 18 12 15 11 0.5 75 170 150 120 150 170 150 120 150 300 300 30 30 13 13 0.75 4.5 0.2 1 45 8.1 6 10 31 31 20 25 31 31 20 25 20 20.5 16 20 15 0.55 100 200 180 160 200 200 180 160 200 400 400 40 40 14 14 1 4.55 0.25 1.5 60 8.2 6.3 14 35 36 25 31 35 36 25 31 24 24.5 20 25 16.6 0.56 120 224 204 164 205 224 204 164 205 460 460 47 47 15 15 1.2 4.6 0.26 1.6 64 Low Marginal Optimum Excessive <250 250‐700 700‐2000 2000+ Guideline Notes For Plant Analysis Calcium and Magnesium: Plant Analysis should be used to confirm deficiencies. Limestone applications generally correct calcium and magnesium deficiencies. Gypsum is a neutral salt and may provide calcium and sulfur nutrients . Chlorides: Chloride levels are routinely corrected with potassium chloride (0‐0‐60). Soil tests required to determine the lbs/acre in the top two feet of the soil. That test number is subtracted from 60 to determine need. Boron: Plant analysis are often necessary to confirm a nutrient deficiency. Alfalfa and various vegetable crops are most sensitive. Annual applications of 2 lbs/acre are typically sufficient, and likewise, limits potential for toxicity. Iron, Manganese, Copper: Plant analysis can be used to confirm deficiencies. A soil test is best used to confirm plant analysis data. Iron‐4ppm, manganese–1ppm, copper‐0.2ppm are considered adequate soil test levels. Magnesium application rates are 50‐100 lbs/acre (broadcast) on a trial basis. Sulfur: Plant analyses are recommended to identify sulfur deficiencies. Critical level is 0.20% for determining sulfur needs. Broadcast and banded applications should be used on a trial basis to determine the most economical response. Plant Analysis – Sufficiency Ranges Crop %Nitrogen Corn 2.5 ‐ 3.5 Soybeans 4.5 ‐ 5.5 Oats/Barley 1.3 ‐ 3.0 Wheat 2.7 ‐ 3.5 Alfalfa 2.5 ‐ 5.0 Grasses 1.8 ‐ 3.0 Zinc ppm Crop Corn 20 ‐ 70 Soybeans 20 ‐ 50 Small Grain 12 ‐ 40 Wheat 20 ‐ 60 Alfalfa 15 ‐ 40 Grasses 20 ‐ 50 %Sulfur 0.2 ‐ 0.6 0.3 ‐ 0.6 0.1 ‐ 0.4 0.1 ‐ 0.4 0.2 ‐ 0.5 0.2 ‐ 0.4 Iron Ppm 30 ‐ 200 30 ‐ 200 25 ‐ 200 25 ‐ 200 30 ‐ 150 50 ‐ 200 %Phosphorus 0.3 ‐ 0.5 0.3 ‐ 0.5 0.2 ‐ 0.4 0.2 ‐ 0.4 0.2 ‐ 0.5 0.3 ‐ 0.5 Manganese Ppm 20 ‐ 150 20 ‐ 100 25 ‐ 150 25 ‐ 150 30 ‐ 100 30 ‐ 150 %Potassium %Calcium 1.8 ‐ 2.6 0.4 ‐ 1.0 1.8 ‐ 3.0 0.4 ‐ 2.0 1.0 ‐ 3.0 0.2 ‐ 0.5 1.5 ‐ 3.0 0.2 ‐ 1.0 1.0 ‐ 2.0 1.0 ‐ 2.0 2.0 ‐ 3.0 0.3 ‐ 0.6 Copper Boron ppm ppm 7 ‐ 20 5 ‐ 25 10 ‐ 40 20 ‐ 40 5 ‐ 20 5 ‐ 15 5 ‐ 25 4 ‐ 30 7 ‐ 15 20 ‐ 60 7 ‐ 15 5 ‐ 15 %Magnesium 0.2 ‐ 0.6 0.3 ‐ 1.5 0.1 ‐ 0.4 0.2 ‐ 0.5 0.2 ‐ 0.5 0.2 ‐ 0.4 Ratios 1. Optimum N:S ratio is about 12:1 for most crops (range of 10‐15). 2. Optimum N:K ratio is about 1.7:1 for most crops (range of 1.2‐2.2). 3. Optimum Fe:Mn ratios should be greater than 1. Relative response of fruit & vegetable crops when soil conditions favor a deficiency. Relative Micronutrient Response Crop Zinc Iron Manganese Molybdenum Copper Boron Apples high – high low medium high Asparagus low medium low low low low Beans, snap high high high low low low Broccoli – high medium medium medium high Blueberries – high low low medium low Cabbage low medium medium medium medium medium Carrots low – medium low high medium Cauliflower – high medium high medium high Celery – – medium low medium high Cucumber – – high – medium low Grapes medium high high low low medium Lettuce medium – high high high medium Onions high – high high high low Parsnips – – medium – medium medium high medium l low low Peas low – Potatoes medium – high low low low Radishes medium – high medium medium medium Raspberries – high high low – medium Spinach high high high high high medium Strawberries – high high – medium medium Sweet corn high medium medium low medium low medium high medium medium medium medium Tomatoes Turnips – – medium medium medium high 1 From R. F. Lucas and B. D. Knezek. 1973. Climatic and Soil Conditions Promoting Micronutrient Deficiencies in Plants. Micronutrients in Agriculture. Soil Science Soc. of America. MVTL: CROP REMOVAL GUIDE CROP P2O5 K20 UNITS ALFALFA 12.6 50 BARLEY 0.4 0.35 BARLEY STOVER 0.15 1.10 BIRDSFOOTTREFOIL 15 60 BLUEGRASS 10 30 CLOVER 15 60 CLOVER (ND) 15 60 CORN (FIELD) 0.375 0.3 CORN SILAGE 3.5 6.5 CORN STOVER 0.25 1.25 DURUM WHEAT 0.6 0.3 EDIBLE BEANS 0.01 0.02 FLAX 15 0.8 GRASS 15 60 HAY 15 60 LEGUME GRASS 15 60 LENTILS 15 60 MALTING BARLEY 0.4 0.35 NAVY BEANS 0.01 0.02 OATS 0.25 0.2 OATS STOVER 0.14 1.20 PASTURE 15 60 0.01 0.02 PINTO BEANS POTATOES 0.14 0.56 RYE 0.6 0.3 SAFFLOWER 0.01 0.01 SORGHUM (GRAIN) 0.14 0.56 SORGHUM SILAGE 3.5 6.5 SORGHUM SUDAN 15 60 SOYBEANS 0.9 1.2 SOYBEAN STOVER 0.3 0.9 SPRING WHEAT 0.6 0.3 SUGARBEETS 0.5 8.33 8.3 SWEETCORN 3.5 WHEAT STOVER 0.12 1.20 WINTER WHEAT 0.6 0.3 TONS BU BU TONS TONS TONS TONS BU TONS BU BU LBS BU TONS TONS TONS LBS BU LBS BU BU TONS LBS CWT BU LBS BU TONS TONS BU BU BU TONS TONS BU BU UM: Use of the Soil Nitrate Test Encouraged Western Minnesota: The use of the soil nitrate test is a key management tool for corn producers in western Minnesota. The nitrate‐N soil test is particularly useful for conditions where elevated residual nitrate‐N is suspected. For this test, soil should be collected from a depth of 6‐24 inches in addition to the 0‐6 inch sample. The corn grower in western Minnesota also has the option of collecting soil from 0‐24 inches and analyzing the sample for nitrate‐nitrogen (NO3‐‐N). When using the soil nitrate test, the amount of fertilizer N required is determined from the following equation: NG = (Table 1 value for corn/corn) ‐ (0.60 * STN(0‐24 in.)) NG = Amount of fertilizer N needed, lb./acre Table 1 value = the amount of fertilizer needed, adjusted for soil potential, value ratio, and risk. STN(0‐24) = Amount of nitrate‐N measured by using the soil nitrate test, lb/acre. South‐central, southeastern, east‐central Minnesota: Research has led to the inclusion of a soil N test to adjust fertilizer N guidelines in south‐central, southeastern, and east‐
central Minnesota. This test, in which soil nitrate‐N is measured in the spring before planting from a two‐foot sampling depth, is an option that can be used to estimate residual N. In implementing this test, the user should first evaluate whether conditions exist for residual N to accumulate. Factors such as previous crop, soil texture, manure history, and preceding rainfall can have a significant effect on accumulation of residual N. A crop rotation that has corn following corn generally provides the greatest potential for significant residual N accumulation. In Chart decision‐aid for determining contrast, when soybean is the previous crop, much less residual the probability of having significant N has been measured. This test should not be used following residual nitrate‐nitrogen in the soil. alfalfa. Nitrogen fertilizer guidelines for corn can be made with or w/out the new soil N test. The University of Minnesota’s N guidelines are still the starting point. A five‐step process is suggested when the soil nitrate‐nitrogen test is considered. 1. Determine N rate guideline using soil productivity, price/value ratio, and previous crop for the specific field. The prescribed rate assumes BMP’s will be followed. See Tables 1, 2, and 3. Table 1. Guidelines for use of nitrogen fertilizer for corn grown on soils considered to be highly productive. corn/soybeans corn/corn N Price/Crop Value Ratio acceptable range MRTN acceptable range
MRTN ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐lb. N/acre‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 0.05 155 130 to 180 120 100 to 140 0.10 140 120 to 165 110 90 to 125 0.15 130 110 to 150 100 80 to 115 0.20 120 100 to 140 85 70 to 100 Table 2. Guidelines for use of nitrogen fertilizer for corn grown on soils considered to have medium productivity potential. N Price/Crop Value Ratio corn/soybeans corn/corn ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐lb. N/acre‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 0.05 130 100 0.10 120 90 0.15 110 80 0.20 100 70 Table 3. Suggested nitrogen guidelines for corn grown on non‐irrigated loamy fine sands with less than 3 % organic matter. Cost/value Ratio Corn/soybean Corn/corn ‐‐‐‐‐‐‐‐ lb N/acre ‐‐‐‐‐‐‐‐‐ 0.05 100 70 0.10 90 60 0.15 80 50 0.20 70 40 MN “N” Guidelines continued … 2. Determine if conditions will influence residual nitrate‐nitrogen levels to increase. This may include previous crop, manure history, and previous fall rainfall. 3. If conditions suggest that a soil nitrate test is warranted, collect a preplant, 0‐24” soil sample representative of entire field, and have analyzed for nitrate‐nitrogen. 4. Determine residual N credit based on the measured soil nitrate‐nitrogen concentrations. 5. Calculate the final N rate by subtracting the residual N credit from the previously determined N guideline. The resulting fertilizer N rate can then be applied either preplant and/or as a sidedress application. This soil nitrate‐nitrogen test should not be used when commercial fertilizer was applied in the previous fall. The variability in the degree of N conversion to nitrate‐N before spring makes this test meaningless in these situations. Residual N credit values based on the concentration of nitrate‐N measured before planting in the spring from the top two feet (0‐24”) of soil. Soil nitrate‐N Residual N credit ‐‐‐‐‐‐‐ ppm ‐‐‐‐‐‐‐ ‐‐‐‐‐ lb N/acre ‐‐‐‐ 0.0 – 6.0 0 6.1 – 9.0 35 9.1 – 12.0 65 12.1 – 15.0 95 15.1 – 18.0 125 > 18.0 155 ISU: Nitrogen Guidelines For Different N and Corn Grain Prices. Corn Following Soybean Corn Following Corn Price Ratio1 Rate2 $/lb:$/bu 1
Range3 Rate Range lb N/acre 0.05 145 126‐169 205 184‐237 0.10 123 108‐144 179 158‐201 0.15 110 92‐126 155 140‐176 0.20 96 82‐112 143 126‐158 Price per lb N divided by the expected corn price. For example, N at $0.25/lb N and corn at $2.50/bu is a 0.10 price ratio. 2
Rate is the lb N/acre that provides the maximum return to N (MRTN). All rates are based on results from the Corn N Rate Calculator as of September 1, 2006. ( http://extension.agron.iastate.edu/soilfertility/nrate.aspx ) 3
Range is the range of profitable N rates that provides a similar economic return to N (within $1.00/acre of the MRTN). ISU: Late Spring Nitrate Test: Yield Goals and Nitrogen Credits Yield goals (or potentials) are no longer used when making N fertilizer recommendations because research has shown no relationship between optimal rates of N fertilization and yields at these optimal rates. The use of legume and/or manure credits has been eliminated. The effects of those sources of N are addressed by giving recommendations for separate categories. Rates of N to apply before crop emergence for in‐season fertilizer applications. N rate (lb. N/acre) Category Corn on recently manured soils 0‐30* Corn after established alfalfa 0‐30* 2nd‐year corn after alfalfa 0‐30 Other corn after corn 50‐125 Corn after soybean (no manure) 0‐75 *These 30‐lb. rates could be applied as a starter. The ISU Late‐Spring Nitrogen Test (LSNT) Continued… The LSNT is a tool that allows site‐specific assessments of plant available N before the crop begins rapid uptake of N. The LSNT can help determine the N needs of corn in‐season, especially on manured fields. This allows adjustment of N applications at sidedress time. For the LSNT, sample the top 12 inches of soil when the corn is between six and twelve inches tall. Iowa State University Extension publication PM 1714, Nitrogen Fertilizer Recommendations for Corn in Iowa, gives more information on how to collect LSNT samples and interpret results. Depth of Soil Sampling Samples collected for the late‐spring soil test must be representative of the surface foot of soil. Manured Soils, First‐year Corn After Alfalfa, and Second‐year Corn After Alfalfa Soils that have received recent applications of animal manures or have decaying sods with alfalfa roots seem to mineralize more plant‐available N after the time of soil sampling than do other soils. These soils, therefore, are treated as a separate category when making N fertilizer recommendations. These recommendations are given in the table below . The first step for making recommendations from Table 3 is to decide whether the top half of the table or the lower half of the table best describes the current prices for grain and fertilizer. Table 3: Nitrogen fertilizer recommendations for manured soilsa and corn after alfalfa. Grain and Soil test Recommended N rate fertilizer nitrate Excessb Normal prices Rainfall Rainfall ‐‐‐‐‐‐‐‐‐ lb. N/acre ‐‐‐‐‐‐‐‐‐ ppm N Unfavorable 0‐10 90 90 (1 bu buys 11‐15 0 60 7 lb. of N) 16‐20 0 0c > 20 0 0 Favorable 0‐10 90 90 (1 bu buys 11‐15 60 60 15 lb. of N) 16‐25 0 30 > 25 0 0 a A field should be considered manured if animal manures were applied with a reasonable degree of uniformity since harvest of the previous crop or in 2 of the past 4 years. b Rainfall should be considered excess if rainfall in May exceeded 5 inches. Addition of 30 lb. N/acre may have no detectable effects on profits, but producers could reasonably elect to apply this rate. c The second step is to decide whether the “excess rainfall” column or the “normal rainfall” column of the table best describes weather conditions before the soils were sampled. The third step is to use the results of the soil test to select the appropriate N rate specified. Interpolation between specified N rates is appropriate when site conditions fall between those given. Nitrogen Fertilizer For Corn After Soybean and Corn After Corn The first step in making a fertilizer recommendation for this crop category is to select a critical concentration for nitrate (i.e., the concentration that distinguishes between adequate and inadequate supplies of available N). A critical concentration of 25 ppm‐N is appropriate in absence of additional information. The second step is to adjust the critical concentration if excess rainfall occurred at the site shortly before the soils were sampled. Reducing the critical concentration by 3 to 5 ppm is advised if rainfall is more than 20 percent above normal amounts between April 1 and time of soil sampling. The third step is to estimate fertilizer needs by subtracting the concentration of soil‐test nitrate (ppm‐N) from the chosen critical concentration (ppm‐N). This value is then multiplied by 8. A factor of 8 is used because studies have shown that it usually takes about 8 lb. of N/acre before planting to increase soil‐test nitrate‐N by 1 ppm. Examples: A soil test of 15 ppm and a critical concentration of 25 ppm results in a recommendation of 80 lb. of N per acre to be applied. (25 ppm ‐ 15 ppm) x 8 = 80 lb. N/acre needed. A soil test of 35 ppm and a critical concentration of 25 ppm indicates that the soil already has approximately 80 lb. of N more than needed. (25 ppm ‐ 35 ppm) x 8 = ‐80 lb. N/acre needed. Reliability of the Soil Test The soil test should be considered only a tool for estimating availability of N in soils. Where Caution is Required The soil test may underestimate amounts of plant available N when (1) nitrification inhibitors or urease inhibitors are applied with fertilizers, (2) more than 150 lb. N/acre are applied as anhydrous ammonia, and (3) more than 150 lb. N/acre are applied as injected manure. Use of the soil test on sandy soils may require deeper sampling if fertilizers are applied before crop emergence and unusually large amounts of rainfall occur between fertilization and sampling. There are relatively few sandy soils in Iowa. TABLE 2 ISU: Estimated Manure Nutrients Available For Crop Production MANAGEMENT SYSTEM LIQUID, PIT Swine Nursery, 25 lbs. Grow‐finish, 150 lbs. (wet/dry) Grow‐finish, 150 lbs. (dry feed) Grow‐finish, 150 lbs. (earthen) Gestation, 400 lbs. Sow and litter‐a, 450 lbs. Farrow‐nursery‐b Farrow‐finish‐c Dairy—confined Cows, 1,200 lbs. or more N P2O5 K2O lbs./1,000 gallons gallons/day 35 58 50 32 25 25 27 44 20 40 42 22 25 20 23 32 20 45 30 20 25 15 22 24 0.2 0.9 1.2 1.2 3.0 3.5 2.2 9.4 25 12 11 18 Heifers, 900 lbs. Calves, 500 lbs. Veal calves, 250 lbs. Dairy herd‐d Beef—confined Mature cows, 1,000 lbs. Finishing, 900 lbs. Feeder calves, 500 lbs. Lagoon­e (all animals) OPEN LOT RUNOFF Earthen lots (liquids) Beef, 400 sq. ft/head Dairy, 1,000 sq. ft/head Swine, 50 sq. ft/head Concrete lots (liquids) Beef, 400 sq. ft/head Dairy, 1,000 sq. ft/head Swine, 50 sq. ft/head MANAGEMENT SYSTEM SOLID MANURE (BEDDED) Swine—confined Nursery, 25 lbs. Grow‐finish, 150 lbs. Gestation, 400 lbs. Sow and litter, 450 lbs. Farrow‐nursery Farrow‐finish Dairy—confined Cows, 1,200 lbs. or more Heifers, 900 lbs. Calves, 500 lbs. Veal calves, 250 lbs. Dairy herd Beef—confined Mature cows, 1,000 lbs. Finishing, 900 lbs. Feeder calves, 500 lbs. Open lot (solids ­ scraped) Beef, 400 sq. ft/head Dairy, 1,000 sq. ft/head Swine, 50 sq. ft/head Poultry Layer, caged, 4 lbs‐f Broiler, litter, 2 lbs. Turkeys, litter, 10 lbs. 25 25 25 25 12 12 12 12 11 11 11 11 8.8 4.9 2.5 18.5 40 40 25 40 25 35 25 35 6.5 35 7.2 3.6 4 3 4 ‐‐‐‐ lbs./1,000 gallons gallons/day 3 3 3 1 1 1 6 6 6 4.9 13.5 0.7 6 6 15 2 2 5 7 7 10 1.6 3.2 0.5 N P2O5 K2O Ton/head/year lbs/Ton 14 14 14 14 14 14 9 9 9 9 9 9 11 11 11 11 11 11 0.34 2.05 2.77 6.16 6.09 12.25 12 12 12 12 12 6 6 6 6 6 12 12 12 12 12 14.0 6.5 1.5 1.1 20.0 12 12 6 12 6 12 6 12 11 12 12.23 22 16 11 6 15 14 lbs/Ton 35 80 65 65 40 40 6.11 14 3 11 11.5 9 1.2 T/1,000 birds/yr 50 10.5 45 9.0 25 35 Con’t … Footnotes for the Manure nutrients table above a Sow and litter figures are per farrowing crate. b Farrow‐nursery figures are per sow in the breeding herd and include one farrowing sow, five gestation sows, and nine nursery pig spaces. c Farrow‐finish figures are per sow in the breeding herd and include one farrowing sow, five gestation sows, nine nursery pigs, and 36 finishing pig spaces. d Per productive cow in the herd; includes lactating cow, 330 days; dry cow, 35 days; heifer, 222 days; and calf, 165 days. e Weights assumed: beef, 1,000 pounds.; dairy, 1,200 pounds.; swine, 150 pounds. f Wet basis at 41 percent moisture. UM: Manure Nutrients Collected form 1994 through 1997 Liquid lb./1000 gal. Solid lb./ton N P2 O 5 K2O N P2O 5 K2O Farrowing 27 27 15 Nursery 34 25 18 Gestation 40 42 18 22 27 14 Finishing 53 39 29 22 22 17 25 15 27 11 7 9 13 12 19 Cows 15 10 9 Steers 14 9 14 44 63 34 Swine Dairy Cows Heifers Beef Poultry Turkeys UM: Manure Fundamentals What is Manure? Manure is not just the urine and feces from livestock, but also the bedding, runoff, spilled feed, parlor wash, and anything else mixed with it. Use of livestock manure is one of the major methods (along with crop rotation and green manure) used throughout history to maintain soil fertility. Since World War II, there have been remarkable developments in the use of inorganic, manufactured fertilizers. Yet manure can still contribute to soil fertility and tilth. In addition to nutrients, manure provides carbon and other constituents that affect soil humus content, biological activity, and soil physical structure. What Does Manure Do in the Soil? Manure is an invaluable way to improve soil, but it can be a major pollutant if you do not pay attention to how it works in the soil. Manure has several effects when added to the soil system: Immediate supply of nutrients. Manure contains nitrogen (as ammonium), phosphorus, potassium, and micronutrients that can be used directly by plants. This is the most commonly recognized value of manure. Delayed supply of nutrients. Other nutrients in manure are part of organic (carbon‐containing) compounds. These compounds trigger biological activity which makes nutrients in the manure and other organic matter available to plants. Lowered pH. Regular manure application lowers soil pH. The acidifying effect of manure is less than that of inorganic fertilizers. Salt and ammonia toxicity. Manure contains high levels of salts that burn leaves when applied to growing plants. Once in the soil, though, salts are not a concern in Minnesota because of adequate rainfall levels. High levels of ammonia or ammonium in fresh manure can be detrimental to germinating seeds. Improved soil structure. The increased biological activity and organic matter improve soil structure by binding soil into aggregates. In the words of S. W. Fletcher in 1910, "When incorporated with the soil, [manure] greatly improves the texture, loosening a heavy compact soil and binding together a light leachy one; making the soil more friable, warmer, more retentive of moisture and more congenial to plants in every way." (S. W. Fletcher, 1910. Soils: How to Handle and Improve Them. Garden City Doubleday, Page & Company, p. 348. ). In some situations, manure can serve as a protective mulch on soils vulnerable to erosion. Enhanced biological activity. Manure affects the mix of organisms in soil, but these changes are poorly studied. Manure may affect pest and nutrient cycles by changing the diversity of soil organisms that compete with pests and that transform plant nutrients. What kind of nitrogen does manure supply? As the figure below shows, about half of the nitrogen in manure is in the form of ammonium and about half is in the form of organic material. Microbes that consume the organic compounds excrete ammonium. One of four things will happen to the ammonium ‐ regardless of whether it comes directly from the manure or from microbes consuming the organic compounds. The ammonium may be: 1. used by plants immediately, 2. converted to ammonia and lost to the air, 3. converted to nitrate which will be used by plants or microbes, leached out of the soil, or denitrified and evaporated, 4. used by microbes. Microbes convert the nutrients to organic compounds which cannot be used by plants or easily lost from the soil. These "immobilized" nutrients become available to plants when the microbes are consumed by other organisms that release ammonium as a waste product. In the warmth of summer, plants and microbes are growing vigorously and use ammonium and nitrate quickly. Losses of nitrate to leaching is greater in spring and fall when fewer plants and microbes can turn it into organic matter. More complex ecosystems (e.g., a pasture with many plant species, a rotation that includes cover crops, or a weedy field,) are more likely to have some plants and microbes active at all times of the year, preventing the loss of nitrogen from the root zone. What Determines the Nutrients in Manure?  Type of animal and age of herd/flock  Feed and feed supplements  Bedding  Collection and storage system  Application method  Timing of application  Soil texture and weather Anytime you change one of these factors, you can expect your manure nutrient test to change. Each of the factors are described below. Type of animal Different animal species produce different types of manure. A ton of fresh manure from most species contains roughly 10 to 20 pounds of nitrogen, 5 to 10 pounds of phosphorus, and 10 to 15 pounds of potassium. However, nitrogen and phosphorus levels are even higher in poultry manure, and sheep manure contains greater potassium levels. Feed Typically, 75% to 90% of the nutrients in feed is not used by animals for growth and is excreted in urine and feces. So it is not surprising that the nutrient content of manure changes when a farmer changes feed sources or when pasture plants change over the seasons. The level of protein and inorganic salts in feed (sodium, calcium, potassium, magnesium, phosphate, and chloride) will be reflected in the characteristics of the manure, and the proportion of available versus organic nitrogen may change. Innovations in feeding practices are dramatically affecting the nutrient value of manure. As you carefully balance feeds for optimal nutrient use by the animals, the nutrients excreted in manure will change. For example, the use of phytase in feed and the use of low phytate corn varieties will improve animal use of phosphorus and will substantially lower the level of phosphorus in manure. Bedding Bedding material absorbs urine, somewhat reducing nitrogen losses. Bedding is more important for changing the rate at which nutrients are available than for changing the nutrient content of manure. Compared to manure alone, the higher carbon content of manure‐plus‐bedding makes less nutrients available in the first year after application (but more in subsequent years). Collection and storage system Manure exposed to sun and wind will lose nitrogen through evaporation. Rain and runoff will leach soluble nitrogen. Phosphorus and potassium losses are negligible in storage except in open systems in which runoff and leaching can cause losses of 20 to 50 percent. Application method Incorporating manure into the soil immediately after application minimizes nitrogen loss to the air and allows soil microorganisms to start decomposing the organic matter, making nutrients available more quickly to the crop. In manure in which half of the nitrogen is in the form of ammonium, about 25% of the nitrogen is lost within the first 24 hours after surface application. Another 20% may be lost in the next 3 days. Nitrogen loss to the air (as ammonia) is greater on dry, windy days, and from the manures of poultry and veal calves. Losses are reduced if it rains shortly after application, and if application is done as the air temperature is dropping (such as in the late afternoon). Phosphorus and potassium are not lost to the air, but they can be carried away in runoff. Solid manure that is allowed to settle out of the liquid may contain 50%‐80% of the phosphorus. This may be important if the liquid is applied separately from the solids. Soil and weather characteristics Decomposition occurs faster under warm, moist conditions, making nutrients available to plants more quickly. Rain after application reduces volatile losses of nitrogen. On coarse textured soils, decomposition is rapid, so nutrients are available more quickly. Coarse soils have a low CEC (cation exchange capacity, or nutrient holding capacity) and low water‐holding capacity, so it may be necessary to limit the amount of manure applied to coarse soils to prevent nutrient leaching. Fine‐textured soils retain nutrients longer in the rooting zone. Infiltration is slower than on coarse‐
textured soils. To prevent runoff, the amount of liquid manure applied to fine soils may have to be limited. Intensive Grazing and Other "Direct Deposit" Approaches One important manure management system that is often neglected is direct deposit of manure onto land by grazing or herded animals. Because animals manage the storage and application components of this system, labor savings are significant. However, nutrients can be lost to runoff and to nitrogen evaporation. These losses can be minimized by mechanically incorporating manure into the soil after herding animals on a plot, or by maintaining a vigorous biological community (e.g., beetles, earthworms, chickens, wild turkeys) that can chop, bury, and decompose the manure so it is quickly fixed into forms that are not easily leached or volatilized. The greatest nitrogen losses are from urine spots because the nitrogen is in an inorganic form and overwhelms the soil’s ability to buffer and immobilize the nitrogen. A "direct deposit" approach to manure management can be used on pastures, hayland, cover crops, and crop fields where livestock clean up residues, weeds, sprouted grains, etc. This strategy is especially suited to areas that will be tilled after the manure is deposited. Two important factors to consider when planning a direct deposit system are irregular distribution and the freshness of the manure. Inevitably, more manure is deposited near watering, feeding, and bedding areas. Urine (with its different mix of nutrients), is typically separated from dung. For these reasons, grazing will greatly increase the variation of nitrogen in the soil across the field. The salt and acid content of fresh urine and manure can have a temporarily dramatic effect on soil and plants. Consider that a urinating cow is applying nitrogen at a rate of 1100 pounds per acre; sheep are applying nitrogen at 250 pounds per acre. Most urine nitrogen is lost to the atmosphere or leaching, in part, because plant growth is reduced by urine scorch. Nutrient Availability from Manure The greatest challenge to supplying crop nutrient requirements from manure sources is balancing supply and demand because the ratio of N:P in manure is very different from that required by crops. Typically, N:P ratios range from 5:1 to 7:1 for liquid dairy manure, 2.5:1 to 3:1 for hog manure, 1.5:1 to 2.2:1 for poultry manure and 3:1 for beef manure. Crops require N:P in the range of 8:1 to 10:1. COLLECTING SAMPLES FOR A
PLANT ANALYSIS
• Corn
– Collect 15-20 plants (or leaves)
– Collect samples random or cross-wise
– Do not collect samples in same row unless trouble-shooting
• Early-Season Plant Analysis (under 12”)
– Whole plant (above ground)
» Check early nutrient availability
• Mid-season Plant Analysis
– Top “fully extended” leaf
» In-season trouble-shooting
• Late-season Plant Analysis
– Leaf “opposite & below” the ear
» Check nutrient levels at critical stage
CORN PLANT ANALYSIS: REPORTS
• Sufficient Ranges @ Silk Stage
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Nitrogen %
Phosphorus %
Potassium %
Sulfur %
Calcium %
Magnesium %
Boron, ppm
Copper, ppm
Iron, ppm
Manganese
Zinc, ppm
(2.5 - 3.5)
(0.3 – 0.5)
(1.8 – 2.6)
(0.2 – 0.6)
(0.4 – 1.0)
(0.2 – 0.6)
(5 – 25)
(7 – 20)
(30 – 200)
(20 – 150)
(20 – 70)
CORNSTALK NITRATES: ISU
• Timing & Collection of Samples
• Kernels reach 80% black-layer
» Annual consistency is vital for comparing data
• Collect 15 (“8” stalk segments) about 6-14” above soil surface
» Stalk is feeding plant with nutrients
• Discard sheaths and damaged material
» Avoid contaminated sample
• Monitoring Nitrogen Efficiency
• Tool is for all corn production, with emphasis on:
» Continuous Corn
» Corn Following Alfalfa
» Corn with Manure History
• Correlates Nitrogen concentration to yield
• 1200ppm is optimum
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Low = 0-250ppm
Marginal = 250-700ppm
Optimum = 700-2000ppm
Excessive = 2000+
Estimated Sulfur Removal
Crop
1. Alfalfa Hay
2. Corn (Grain)
3. Corn (Silage)
4. Small Grains
5. Soybeans
6. Soyb + straw
Sulfur Content
6.0 lbs/ton
0.09 lbs./bushel
1.50 lbs./ton
0.16 lbs./bushel
0.16 lbs./bushel
0.40 lbs/bushel
Available Sulfur in Manure
Source
Horse
Cattle
Sheep
Swine
Poultry*
Solid (lbs/ton)
Total/Available
1.4
0
1.6
0.9
1.8
0
2.7
1.5
3.2
1.8
Liquid (lbs/1000g)
Total/Available
0
0
4.5
2.5
0
0
7.6
4.2
9.0
5.0
Note: ½ of manures total Sulfur becomes available
*Includes floor litter.
GYPSUM: CALCIUM SULFATE
• Improve Soil Structure
– Flocculation (increases clay particle size)
– Improve water infiltration
– Decrease crusting
– Calcium Replaces Sodium
– Sodium is available to leach as sodium-sulfate
– Decreases the pH of Sodic Soils
• Correct deficiencies (Mg) and/or Excessive Levels (Na)
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Calcium (Ca) = 65-75% Base Saturation
Magnesium (Mg) = 15-20% Base Saturation
Potassium (K) = 2-7% Base Saturation
Sodium (Na) = 1-5% Base Saturation
• Managing Ratios
– Research data does not show an economical return
Sulfur as a Nutrient
• Essential for protein synthesis.
• Helps develop enzymes
• Promote nodule formation in legumes.
• Aids seed production.
• Influences chlorophyll production.
Sulfur Sources
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Soil mineralization of organic matter.
Subsoil sulfate.
Manure.
Crop residue.
Atmosphere decomposition.
Irrigation water.
Commercial Fertilizer.
Sulfur Availability
• The soil organic matter and subsoil sulfate are
key sources of plant available S.
• 95% of the S in the soil is organic and
unavailable to plants. Plants require sulfate
(SO4-).
• About 3 lbs./percent organic matter/year is
considered available to crops. Plant available S
can range from 10-200 lbs depending on soil.
Estimated Sulfur Removal
Crop
1. Alfalfa Hay
2. Corn (Grain)
3. Corn (Silage)
4. Small Grains
5. Soybeans
6. Soyb + straw
Sulfur Content
6.0 lbs/ton
0.09 lbs./bushel
1.50 lbs./ton
0.16 lbs./bushel
0.16 lbs./bushel
0.40 lbs/bushel
Available Sulfur in Manure
Solid (lbs/ton)
Source Total/Available
Horse
1.4
0
Cattle
1.6
0.9
Sheep
1.8
0
Swine
2.7
1.5
Poultry*
3.2
1.8
Liquid (lbs/1000g)
Total/Available
0
0
4.5
2.5
0
0
7.6
4.2
9.0
5.0
Note: ½ of manures total Sulfur becomes available
*Includes floor litter.