Evaluating the Use of Soil Moisture Monitoring Equipment under cereal crop production in the SA Mallee By Jeremy Nelson, South Australian Murray Darling Basin Natural Resource Management Board, Berri, South Australia. MSF Waikerie Core Site Throughout 2010 the South Australian Murray‐
Darling Basin NRM Board established 3 capacitance probe based soil moisture monitoring sites under cereal crops in the SA Mallee. These sites are spread between Waikerie, Pinaroo and Karoonda. As soil calibration data was pending for the Pinaroo and Karoonda sites this article will discuss results at the MSF Waikerie site for the 2010 season. All of these capacitance probe installations have been undertaken in conjunction with support from Caring for Our Country as part of the ‘Engaging Farmers in Improved NRM’ project. This four year project is currently in the second year of implementation, so results for trial work should be considered as preliminary. This article will deal specifically with the Waikerie MSF site installations, including discussing the installation and calibration process to date. A review of monitoring results from the 2010 season will also be reviewed. componentry) and given that they have a preset distance set between them, they function as a plate style capacitor when an electrical charge is running through them. Hence when electrically active (although separated from the soil by a thin PVC wall) the soil acts as the ‘dielectric’ between the two electrodes. A dielectric is generally equated to an insulator material that can be polarized by an induced electrical field. When electrical activity is occurring this then enables a measure of the ‘permittivity’ of the soil media to the electrical activity to be measured. Permittivity is equated to how an electrical field affects a dielectric medium (in this case the soil) and conversely how the dielectric medium affects the electrical field. This is generally interpreted predominantly by the level of resistance encountered by the probe to the establishment of an induced electrical field in the dielectric or the soil. In practice as soil moisture levels change the probe recognises a change in the capacitance property of the soil which corresponds to a fluctuation of the dielectric’s permittivity and associated changes in electrical field responses and behaviours. Probe signal response data is then conveyed, interpreted and displayed graphically as a trace or as numeric data for user evaluation. What is Capacitance Probe Technology? Put simply capacitance probe technology can be essentially defined as technology which utilizes the principal of ‘Dielectric Permittivity’ to ultimately generate graphical interpretations of levels of soil moisture. To understand this an examination of a probe’s construction reveals strategically mounted sensor heads at pre‐set depths along the probes body. A simplistic explanation of the function of these sensor heads is that generally they consist of metal rings which function as electrodes (with other Figure 1: View of the Capacitance Probe setups installed at the Pinaroo and Lowaldie sites. The smaller ‘plug in’ probe covers the 0‐10 cm soil layer and is removed prior to harvesting and seeding leaving the main unit (40cm in this case) in field set below cultivation/seeding depth. This is a very simplified explanation of the underlying technology that supports the operation of capacitance probe technology. to visit sites. This is a vast time saving compared to earlier eras where logging was undertaken manually on a per site and per event basis. The encapsulation of this technology within a PVC tube with multiple sensors at specific depths has culminated in the commercially available ‘Capacitance Probe’ that is available today. Capacitance probe technology should not to be confused with ‘Tension’ based soil moisture monitoring systems which produce estimates of soil tension generally measured in kilopascals. This technology which utilizes gypsum based block sensors is not recommended for dryland situations. Tension based technology performs best when good soil/tension block contact is maintained through a moist soil ‐ as such this technology is best left for irrigated situations. Aims of the trial The Waikerie site installation differs somewhat in purpose to the Pinaroo and Lowaldie sites in that the nest of 4 probes were installed in strip plots to examine the additional affects of stubble retention/removal in alternate strips over time. As such the aims of the Waikerie trial are to: Figure 2: View of Waikerie probe setup site. Solar panels provide battery recharge and transmission towers hold up transmitters which relay information telemetrically. Submerged cabling runs from the in field probes back to these towers. Optional automated rain gauge in foreground provides on site logged rainfall. Extensive improvement of commercially available probes over the past 10‐15 years has significantly upgraded the performance and reliability of the technology and associated systems. This means that continuously logged data is now generally relayed telemetrically from a transmission unit to either an on‐site system or to a server facility that can be accessed remotely. This improvement now means that a continuous picture of soil moisture can be accessed either off of hand held technology or a PC (when hosted on an internet ready server) without the requirement 1. Install probes and calibrate them to soil characteristics to enable estimates of Plant Available Water (PAW) to be derived throughout the year; 2. Develop a better understanding of the impacts of rainfall, crop water use, weed water use and ground cover retention on overall soil moisture levels over a four year period; 3. Assess how well the use of capacitance probe data can influence on farm decision making throughout the year, including examining how this technology can interact with yield forecasting tools and derived ETo and associated data sources. As previously mentioned this article will deal specifically with examining the results associated with point 1 as results against points 2 and 3 will be achieved over the next two years. MSF Waikerie Soil Moisture Monitoring site At the Waikerie MSF site 90cm probes have been installed in a nest of 4 in strip plots measuring 6 metres wide and some 30 metres long. This situated the actual probes well within a cropped area immediately adjacent a fence line where the two transmission towers and logging rain bucket were situated. Cable length limitations and proximity to an Automatic Weather Station and the main area of the core site were major factors that dominated the site selection. Soil characterisation is discussed in the following soil calibration results. Soil and probe calibration activities As part of the trial work calibration of all probe sites has been undertaken. In essence this equates to attempting to reconcile probe response measurements of plant available water (PAW) to actual physically measured amounts of PAW. To enable this to happen two main activities were undertaken: • Soil coring and gravimetric analysis, or the laboratory measurement of physical amounts of actual stored soil moisture and a determination of the stored soil moisture fraction that is PAW; • Utilization of the above to allow adjustment of capacitance probe monitoring values of PAW back to actual figures of measured PAW. This is achieved essentially by applying an adjustment factor back to the probe values to correct them. The first activity involved characterisation of the soil moisture holding potential of the soils, including deriving limits related to the Drained Upper Limit (DUL) or the point at which the soil texture is no longer able hold introduced moisture and drainage occurs and the Crop Lower Limit (CLL). The CLL is the point at which soil moisture levels have diminished to the point where severe plant water stress occurs, i.e. the plant is no longer able to access any miniscule amounts of stored soil water. Please note that the determination of the drained upper limit is an ongoing calibration activity, current values are based on published soil values.1 At the Waikerie site physical soil water levels were determined by collecting three soil cores at each 1
http://bettersoils.soilwater.com.au moisture probe location to 100cm to reflect the depth to which the soil probes are operating at. Gravimetric soil water was determined at 10 cm increments for each of these cores. The resultant gravimetric analysis of soil water values for each 10 cm layer were averaged together to give an average gravimetric soil water for each depth that the soil probe measures per the three coring sites. A soil texture was also determined for each of these layers. Volumetric water was then calculated for each layer by assuming a bulk density of 1.5 gcm3 for the topsoil (0 – 10 cm layer) and 1.6 gcm3 for all soil layers greater than 10 cm depth. From here, soil texture was used to estimate the crop lower limit of each soil layer using published wilting points.1 Where the volumetric water was less than the published crop lower limit, the measured volumetric water was used as the crop lower limit for that layer. Gravel adjusted estimates of PAW for the Waikerie Site produced the following results with the formula being: Determined Volumetric Water (%) – Determined Crop Lower Limit (%) = PAW Content per depth interval in mm. Depth Interval 0‐10cm 10‐20cm 20‐30cm 30‐40cm 40‐50cm 50‐60cm 60‐70cm 70‐80cm 80‐90cm 90‐100cm Total PAW (mm) Core 1 PAW (mm) 13.54 13.53 14.03 14.82 10.65 10.63 5.73 7.08 1.25 ‐0.68 90.58 Core 2 PAW (mm) 6.40 14.49 15.61 17.45 10.32 10.01 9.38 6.70 ‐0.82 0.34 89.88 Core 3 PAW (mm) 11.77 17.86 14.07 9.97 11.07 11.31 9.14 8.18 0.46 ‐0.40 93.43 Figure 3: PAW results from gravimetrics at the Waikerie MSF site. Soil textures were predominantly Loamy Sand in the upper 40cm grading down to Sandy Clay Loams at depth. Carbonate presence was high below 40‐
50cm depth, as was the presence of limestone marl. The presence of varying levels of marl/gravel between cores accounted for most of the variation in determined PAW content. The summary soil analysis results were subsequently applied to the calibration facility of the capacitance probes via the relevant operating software. Importantly an average of the three PAW results was applied to the Soil Moisture Sum function, i.e. the total PAW values were applied to the equivalent default sum of whole probe values. This was done to avoid from the outset the necessity to have to calibrate each of the eight sensors across each of the four probes to their specific PAW value. As such the water holding capacity results obtained from the average of the soil analysis (e.g. 90 mm) were divided by the total moisture obtained from the soil probe (eg 98mm). This then enabled a new calculation extension to be created which effectively had a coefficient effect when applied back to the probe values. For this article this will be referred to as the ‘offset factor’. As such to determine the calibrated total moisture in mm the following simple method was applied; Total Summed Soil Moisture (probe calibrated) = Total Summed Soil Moisture (probe) x offset factor In practice these varied between the four probes in values ranging from 1.3 to .8. What this means in real terms is that there is an estimated deviation potential of between 10‐20% in displayed data either end of the scale.2 Therefore it is reasonable to recommend based on the calibration process to date and the performance of the Enviropro probes and Adcon system that monitored values can be interpreted with medium to high certainty. 2
Adcon Telemetry (probe retailer and calibrater) recommendation Further to this, this certainty will likely be improved in the next phase of this trial project. It is worth noting additionally that this project is attempting to identify the cumulative worth of the calibration process against apparent benefits. This will need to be done if a valid case is to be made to on farm investors that both the technology and the associated calibration setup will be a worthwhile investment on farm. Capacitance Probe system operation The sites that have been setup at the Waikerie MSF Core Site by the SAMDBNRM Board consist of 4 main components; 1. Independent top level roll out moisture sensor, (Stevens Hydraprobe) which supplies soil moisture data for the top 10cm of soil; 2. Standard ‘potted’ probe (Enviropro) which consists of a stack of 6 sensors which provide soil moisture, temperature and conductivity data for 20, 30, 40, 50, 70 and 90cm soil layers. These sensors are mounted and secured in a moisture proof plastic body. 3. Logging rain gauge (logging at .2mm tipping intervals), and; 4. Transmission assembly, including solar panels, towers, cabling etc. Essentially the systems are stand alone and battery voltage at the data logging units is boosted by continued solar recharge of the batteries during the daytime period. Data received at the logger is transmitted by the NextG phone network to a server facility hosted by the retailer of the probe system and is uploaded to a website where users can access the data by logging in. As can be seen in the following figure 4 the rollout top level sensor is located to provide data results for the top 10cm of soil data. This therefore means that the potted section of the probe located at the 20cm mark is left in the ground permanently and that the periodic removal of the top level sensor allows for periodic working of the site including seeding activities. http://165.228.207.51:8081 If you experience any further difficulties accessing the site it may be necessary to ‘enable popus for the site’ within your security preferences, please phone 0429 845 216 if you need advice on this point. Step 2: Make sure you select in the resultant search: adcontelemetry.com.au Step 3: On the main Adcon page scroll down to the Demo Server and click the link: Go to Demo Server which will take you to the login page to access the sites
Figure 4: Completed installation of potted and removable probe. Cable length limitations mean that locating a site on farm generally means locating the control towers against fence lines and then radiating out probe locations from these points The top level sensor which is installed immediately after sowing and removed immediately prior to harvesting, spends the out of season period logging soil moisture at a location clear of tillage/seeding activities, e.g. along a fenceline. Click ‘Go to Demo Server’
Accessing site data To access the soil moisture monitoring results for the Waikerie, Pinaroo and Lowaldie sites it will be necessary to use a PC and an internet browser such as Internet Explorer or Mozilla Firefox. Step 4: When prompted to login type in the following: Username: samdb, Password: mdbuser on the login page as per following: It is important to note that the data is hosted by Adcon Telemetry which has local and international branches, as such it is essential to access the South Australian branch of Adcon as Step 1 at: www.adcontelemetry.com.au Data for the sites is not available through the other branches. It is recommended that dependent on your browser that you use either the main search facility in Mozilla Firefox or a Google toolbar only in Internet Explorer or another browser. It is not recommended to use toolbars such as Ask.com or Alot etc as experience has shown that they will not locate the site. Alternatively the following URL address can be used in the recommended searching toolbars: Once the logins have been typed in press ‘enter’ and you should now be taken to a website which displays as follows: required and then using the period bar to select a suitable duration. Use < or > arrows to scroll between month options. The other most prominent tools that will need to be used on all of these sites are further right on the same bar. If you move the mouse across these icons without clicking pop ups will tell you what each one does. Essentially these tools are: Double Click ‘Buckley P2 Soil Moisture salinity temperature 30cm’ Step 5: To get started, scroll down to the Buckley’s sites and you will notice that there are four probe sites, double click ONLY on Probe 2 (as only one has been made available on this site) and then double click firstly on ‘Buckley P2 Soil moisture salinity temperature.’ Show values at cursor: allows you to click and drag a cursor bar across the data and access automatically derived summaries of trace information in two ways. The most common method will generate values at the cursor bar as you move it across the graph. The second method which is activated by clicking the tool icon will allow the clicking and dragging across a graph area to show min/average/max and summed values for all graph traces; Always jump to last available data: allows quick page cuing to the most recent logged data, as opposed to manual selection using the previously described time frame selection process. Graphical view: is the current view where data is presented in graphical traces and lines of device interpreted responses to soil moisture; You should now see a combined summary of soil temperature, summed soil moisture levels (expressed in mm/m) for the 20‐30 cm soil profile and a conductivity response (which can be equated to increases in the presence of ions and other materials that increase the conductivity of the soil). Step 6: At this point it is necessary to discuss some basic site navigation. You will note the green strip running across the web page houses date and time scale options as well as some tool icons, these are now discussed in further detail. Their application can be used in viewing any of the Waikerie, Lowaldie or Pinaroo information. First and foremost setting a period of time to view site data should be nominated. This is essentially achieved by dropping down the date from the date bar and selecting the date of commencement Table view: is the opposite to graphical; if selected the same data is available, but as line entry data which correspond to logging events occurring every 15 minutes. This data is useful in pinpointing exact details of logged events, including the onset of the increase of soil moisture, temp and conductivity responses to soil moisture increase or decrease. Virtual instruments: provide outputs which can be accessed and more easily viewed with the use of a smart phone or equivalent, they are essentially a graphical depiction of data that can be readily viewed and interpreted. These icon displays are designed to be easily visible on hand held technology. Step 7: To utilize these tools it is suggested to firstly click out of the current page by cancelling it with the red X icon in the upper right hand of the page and then in the graph options page double click on: ‘Buckley P2 Soil Moisture Stacked’. This is a popular view that shows individual SMM trends per sensor depth, note that the upper level HP sensor was installed some time after the main probes, hence the data gap. Click ‘show values at cursor’ icon This view of data is with the summed graph function the most common way of viewing soil moisture monitoring results. Rainfall is featuring in this instance as vertical blue lines emanating from the X axis, relationships between the incidence of rainfall and the behaviour of soil moisture are instantly apparent. This particular graph shows the monitoring results of each sensor depth ‐ 0‐10cm, 10‐20cm etc in a depth by depth comparison of soil moisture per 10cm soil strata. Note the impacts of rainfall reflect in soil moisture increases commonly referred to as ‘spikes’ and the drying down of the soil, including drainage and the effects of plant water use contribute to the slumping of moisture levels. When a soil is largely dry a flatline type of trace is apparent. Note that whilst a scale in mm/m is provided for the upper level sensor calibration of these values is yet to occur. Step 8: To get some more meaning out of this graph the utilization of the cursor tool is now recommended. This tool (which appears as a vertical black line which activates when you click in the graph area) displays in two ways as a kind of toggle feature. As can be seen this default method which is a quick reference function shows values at the cursor per trace and includes rainfall data. However better rainfall data is accessed by enabling the secondary cursor function which is enabled by clicking the ‘Show values at cursor’ icon as indicated above. Now by clicking, dragging and holding the cursor across the page until the period of interest is determined a blue trace will appear. Release the mouse button when the period of interest has been selected and summary boxes of information for each trace level will appear on the bottom of the screen, including a rainfall summary for the site/period of interest. Note: if you have difficulty seeing the rainfall summary de‐activate the display of the 90cm probe in the left hand column by clicking on the tick box and then repeat the selection process until all information is visible. Interpreting this information: You will note as opposed to the values generated at the trace per cursor that the secondary method of accessing values generates summed, minimum, average and maximum values for each sensor and rainfall. to facilitate this graph’s function. As such this graph depicts at any point in time (based on the previously described calibration process) an estimation of the amount of moisture available to crop for transpiration. Please note that the summed values in this view are a sum of the total’s of the logging events and are not reflecting actual moisture increases. The min/average/max values do provide important values however as do the rainfall summaries. Step 9: Now click out of this page and on the probe list page double click on ‘Buckley P2 Soil Moisture Sum’. Importantly this page features data that currently has the highest confidence attached to the PAW estimates. 2010 Season Results – using the data to date The previous discussion provides not only a basic summary of the tools available through the soil moisture monitoring system but also serves as a basic tutorial for the use of the system and the graphing functions. As such it Drained Upper Limit (DUL) or the point at which the crop reaches field capacity and Crop Lower Limit (CLL) have been integrated on the Y axis together with value ranges. The graph trace portrayed here represents a total soil moisture value for the entire 100cm of soil monitored. This is accompanied by the usual rainfall stats received on site. Graphically the positioning of the DUL and CLL show how overall soil moisture performed against these upper and lower limits of soil moisture holding capacity. In the near future further calibration activities will seek to assign similar parameters to each level sensor individually. Step 10: Click out of this page and back to the probe listing page and now double click on ‘Buckley P2 Soil Moisture Summary’. This page differs from the summed in that it takes the summed data and utilizes a simple formula: Soil Moisture Summed (mm’s) – Crop Lower Limit (mm’s) = mm’s of moisture remaining In turning to month by month comparisons the following summaries of soil moisture and rainfall are now possible in light of the previous discussion. What is not possible within the space of this publication is to delve into analyses of each of the graph functions, however as discussed in the calibration section of this article greatest confidence is currently held in PAW estimates stemming from the summed graphing functions. The analysis discussed in this section was developed using the ‘Show values at Cursor’ function described in the previous section. However the selected views (which display in blue) have been dropped for an unselected view for the sake of this publication, else wise they would be difficult to discern once reprinted. The ‘show values at cursor’ function allows whole of month summaries to be rapidly accessed. If possible the reader is encouraged to access the sites as previously described and follow these month by month comparisons through. See the previous section for website access information. The probe graph accessed is ‘Buckley P2 Soil Moisture Summary’ This graph has the in built equation of Soil Moisture Summed (mm’s) – Crop Lower Limit (mm’s) = mm’s of moisture remaining Therefore the graph is designed to be readily interpreted as mm’s of plant available content available at a specific time. This graph it is suggested will be of highest direct benefit to users of this data currently. With the equipment installed the beginnings of a summary soil moisture trace can be seen at the right of the middle screen. Plant available water at this time averaged 23.74 mm’s of PAW, a modest opening season soil moisture. Logged rainfall for this month was also a low 16.6 mm’s. August 2010 Crop water use pattern – ‘diurnal stepping’ or day/night trends April 2010 Installation of the equipment had not yet occurred in April, however the Waikerie AWS recorded 19.6mm of rainfall as an opening to the growing season. May 2010 Initial installation of the soil moisture monitoring equipment occurred in May, however due to the upper level sensor not being installed till July a prognosis of total soil moisture during this time was not possible. During August conditions remained very dry. Rainfall for the month totalled 26.8 mm and plant available water had reduced further to a mere 18.88 mm’s. The spread of smaller rainfall events can be seen by the blue vertical bars on the X axis. The strong occurrence of ‘diurnal stepping’ shows the vigorous drawdown of soil moisture by an actively growing crop. This reflects a drawdown of soil moisture reserves in the daytime to meet transpiration demands, followed by a corresponding rest period at night where transpiration ceases in the absence of sunlight. Each ‘step’ correlates to one day of plant life. The wheat crop was sown on May 18, 2010. Rainfall logged at the site for this month totalled 40.8 mm’s. June 2010 Similar to above, rainfall logged at the site totalled 7.4 mm’s September 2010 September rainfall events boost up soil moisture which was approaching the CLL July 2010 September is where it is possible to see how the 2010 season began to deviate drastically from the previous season. Those who had crop in in 2009 water use period a reduction in response to weather conditions produced an average of 2.4mm’s of daily reference crop water use.3 would remember the harsh September that worked against grain fill in that season. On the extreme right hand side of the screen we can see that soil moisture at this time was trailing at a low of around 11 mm’s of PAW. A substantial group of rainfall events (vertical blue bars) equating to 37.8 mm’s then buoys up flagging soil moistures enabling crops to push on through the early spring period. Rainfall events in the middle of October then as with September buoyed up soil moistures, enabling crops to push on further. Plant water demand tapers then recommences prior to being once again allayed by further rainfall events. November 2010 This event combined with the other noticeable rainfall events in mid September created improved soil moisture conditions which assisted grain filling. Total rainfall for the period equated to 64.8mm’s. Upper level sensor removal October 2010 Heavy crop water demand Period of low transpiration activity
During October the beneficial rainfall events of September meant that the extra 51.6 mm’s of rainfall received during this period could be further utilized by maturing crops. By the 13th of September however soil moisture levels were once again flagging close to the CLL. Once again a burst of rainfall events equating to 35 mm’s pushed up rainfall enough to stabilise PAW levels. By November it is apparent that crops have transpired a lot of the available moisture and benefits derived by good rains in September and October. PAW levels diminish to an average of 5.18 mm’s, however crop water use remains vigorous immediately prior to harvest around mid November. The trough effect at this point shows the point at which the upper level sensor was removed and re‐
installed against the fence line. Total rainfall received in this month was 19.2 mm’s. December 2010 What is interesting to point out in this graph is that after these rainfall events transpiration activity was reduced drastically as the accompanying weather revealed a reduction in calculated reference crop evapo‐transpiration (ETo) rates at the Waikerie Weather Station site. During the heavy water use period on the left of the screen, calculated ETo totalled and average of 4.2mm’s of reference crop water use, whereas in the low 3
Waikerie Dryland AWS site. Reference Crop ETo calculation (Penman Monteith method). Although out of growing season the December graph is worth considering as the phenomenal rainfall received in that month graphically demonstrates. A total of 156.6 mm’s of rainfall was received at this site in December, evidenced by the staggering rainfall bars. PAW which had been flagging after the latter stages of crop finish correspondingly rockets to an average of 46.82 mm’s of plant available water. The importance of this event from a calibration perspective is that an examination of the separate layer graphs showed that drainage had occurred at every sensor depth. Therefore it would appear that the maximum PAW this soil profile can hold is some 80mm’s, based on the calibration process and the values on the Y axis. However what needs to be remembered is that the crop is likely to only access moisture to 40cm due to the heavy carbonate presence in the soil. Once individual layer calibrations have been achieved it will be possible to estimate PAW within the effective rootzone of the crop more accurately. This obviously ‐ (combined with further rainfall events since) has set the stage for problematic and enduring summer weed growth at the site. An examination of weed impacts on moisture levels at the site will continue during 2011. Summary of quick stats from the Waikerie MSF Soil Moisture Monitoring Site: Total maximum estimated PAW for soil type (0‐100cm) 2010 Opening Season PAW content (Summed) (Earliest reading possible in July) Closing season PAW content (Summed) (taken immediately prior to harvest. PAW content as at February 16 2011 Rainfall statistics from Waikerie Total Growing Season Rainfall April to October Out of season rainfall to date (December 2010 to February 16, 2011) Yield estimate for site (no actual yield data was available in 2010) Conclusion 85mm 23.74 mm’s average 6.15 mm’s average 31.48mm’s average 227.6 mm’s 222.8 mm’s The first phase of the trial has focussed heavily on establishment and calibration. The second phase of this trial will now seek to link monitored soil moisture to crop growth, performance and yield. There are also interesting links to N application and calculation that will be explored. To date the trial work has shown that there is an emerging role for the capacitance probe to play on the dryland farm. It would appear also that calibrated probe results hold the greatest promise in terms of providing results that will be able to effectively interact with a suite of other tools, such as APSIM. Obviously the technology must be viewed within the limitations that will likely continue to surround the absolute confidence in monitored values. However it is apparent that both the technology and the means of calibration afford relatively good results for the effort. What is essential to understand is that the capacitance probe is providing point source information from a specific site within a broad acre situation. One of the questions that this project is attempting to address over time is just what would constitute an effective system setup for an average farm size? If a zonal approach to multi probe installations was undertaken on farm what would be the cost/benefits for landholders? As with a lot of precision agricultural technology it is likely that the role and full functionality of the capacitance probe is yet to be fully exploited in the dryland situation. It is hoped that this trial work and project will ultimately provide a good basis for landholders to evaluate the technology and it’s uses within their own farming systems. Jeremy Nelson [email protected] Mobile: 0429 845 216 Office: 8582 4477 1.8 tonnes/ha PO Box 1374, Berri SA, 5343