I
D
A
H
O
Potassium Fertilization of
Russet Burbank Potatoes
By D.T. Westermann and T.A. Tindall
P
otato tuber yields over 500 cwt per the growing point, as well as vine,
acre are being achieved by many of roots and tubers periodically sampled
Idaho’s potato growers. At this pro- between early tuber growth and vine kill.
duction level, over 240 lb K2O/A can be Tuber yields, grades, and internal quality
removed by the tubers. Historic soil test were determined for each plot at normal
information shows that extractable K con- harvest.
centrations have declined
Fertilizer Rate
from more than 400 parts
A recent study re-evaluated
Recommendations
per million (ppm) in the
the potassium (K) fertilizer
Total tuber yields across
late 1960s to the range of
requirements of Russet
the experiments ranged
100 to 200 ppm now.
Burbank potato production
from a low of 350 cwt/A to
Five experiments were
under today’s soil conditions
nearly 600 cwt per acre.
conducted on growers’
and higher yield potentials.
Yield responses to K fertilfields between 1992 and
Potassium fertilization rates
ization were from none to
1995 with selected K
should be increased over
nearly 100 cwt/A. Tuber
rates, sources, placement
what was previously considexternal quality parameor timing variables, inered adequate, particularly
ters were generally high
cluding K-fertigation as
on coarse textured soils.
(greater than 70 percent
treatments. Preplant broadcast applications were applied before U.S. #1 tubers), except for the lowest
spring tillage preceding planting, while yielding experiment where other managebanded K was placed in a single band 4 ment factors affected yield. The 1987
to 6 inches adjacent to the seed piece University of Idaho fertilizer guide for
after planting.
Simulated K-fertigation applications TABLE 1. Comparison of K fertilization rates at
different soil test K concentration in 0
were accomplished by spraying K soluto 12 inches of soil.
tions on during a sprinkler irrigation.
Soil
Recommendations
Potassium sources were potassium sulfate
test K,
1987
1992-95
(K2SO4), potassium chloride (KCl) or
ppm
lb K2O/A
lb K2O/A
potassium thiosulfate (KTS). Soil textures
25
250
600
varied from a silt loam to loamy sand,
50
200
500
sodium bicarbonate (NaHCO3) extract75
150
400
able soil K concentrations from 85 to 126
100
100
300
ppm in the top 12 inches of soil. The K
125
50
200
150
0
100
status of each treatment was monitored by
175
0
0
sampling the fourth mature petiole from
8
Better Crops/Vol. 82 (1998, No. 2)
potatoes contained a critical
soil test K concentration of
150 ppm K in the top 12
inches of soil (NaHCO3
extractable). Tuber yield
data summarization from our
studies showed that the concentration
should
be
increased to 175 ppm K
(Table 1). While this was
not a large change, the K fertilization rate necessary to
achieve maximum yields did
change significantly. For Potassium deficiency symptoms on leaves of potato plants.
example, the optimum K fertilization rate at a soil test K concentration particularly as KCl. Growers should con(STKC) of 100 ppm was 300 lb K2O/A in sider other application options if they
our study compared with 100 lb K2O/A need to apply more than 300 lb K2O/A
recommended in the 1987 fertilizer guide. such as applying a portion the previous
Similar changes occurred at other STKCs. fall or splitting the preplant application
Growers may want to add 50 lb K2O/A to between KCl and K2SO4.
the rates in Table 1 for each 100 cwt/A
tuber yield above 400 cwt to maintain Fertigation and Petiole K
their soil test K concentrations.
Concentrations
Petiole K concentrations decreased
Source and Timing Effects
with time after tuber initiation. ConcenTotal tuber yields were generally 5 to trations were generally higher with broad10 percent higher with K2SO4 than with cast K compared with either banding or
KCl at the optimum fertilization rate fertigation treatments. Petiole K concenapplied preplant. The higher yield was trations should be above 6.5 to 7.0 perfrom an increased yield of U.S. #1 tubers cent until 30 days before vine kill to pregreater than 10 oz. Both K sources vent K from limiting tuber yields in southdecreased specific gravities. However, ern Idaho. Petiole K concentration restubers receiving KCl generally had gravi- ponses to K-fertigation applications were
ties 0.001 to 0.004 units lower than those slow, up to 15 to 20 days after an applicareceiving K2SO4. At K fertilization rates tion. A preferred K-fertigation source was
greater than optimum, both sources had not identified. Individual K-fertigation
similar effects.
applications should not exceed 30 lb
A preplant K application was more K2O/A during tuber growth and should
effective than splitting the same amount not be made within 30 days before vine
between preplant and fertigation or apply- kill. Potassium fertigation applications
ing all the fertilizer via fertigation during may need to be repeated, but should not
tuber growth. In addition, preplant broad- be closer than a 10 to 14 day internal.
casting was more effective than banding
the K fertilizer shortly after planting. Summary
Spring preplant applications higher than
Potassium fertilization rates for
300 lb K2O tended to decrease yields,
(continued on page 12)
Better Crops/Vol. 82 (1998, No. 2)
9
Summary
TABLE 4. Influence of P fertilizer application timing
Data from the P timing studies,
on rice grain yield from three P timing
studies conducted during 1997.
and other P fertilization projects conducted during 1997 on alkaline silt
P
Grain yield, bu/A
loams, continue to show significant
Timing
Brooks
Davis
Wimpy
TDM and yield increases from P ferPreemerge (PE)
184
145
150
tilization. Generally, acidic silt loam
Preflood (PF)
171
143
156
soils with acidic pH and following
Postflood (POF)
172
157
156
soybean in rotation have not shown
Midseason (MS)
182
131
147
rice yield increases from P fertilizaLSD (0.05)
NS
18
NS
Pr > F
0.611
0.018
0.410
tion in Arkansas. Fields that have
CV %
14.6
15.4
9.3
been precision graded are an exception, since they typically respond to P
fertilization for several years following lev- P response. More studies are needed to
eling, regardless of pH. Phosphorus timing establish consistent trends among P applistudies conducted during 1997 indicate cation timings. Present and future research
that P should be applied before or during efforts are focused on development of more
vegetative growth. Phosphorus applications accurate P recommendations for rice.
made at MS in these field studies tended to
produce lower yields than earlier applica- The authors are with the Department of Agronomy,
tions on P responsive soils. Data also indi- University of Arkansas. Dr. Slaton is Extension
cate that some benefit was obtained from Agronomist-Rice, located at the Rice Research
either PF or POF P application at the Extension Center, Stuttgart. Dr. Wilson is Extension
Wimpy site. Additionally, yield data from Rice Specialist/Research Associate Professor, located
the Davis farm indicate that P applied at Monticello. Dr. Ntamatungiro is research specialist,
before emergence may be subject to fixa- located at Stuttgart. Dr. Norman is Professor of Soil
tion. Phosphorus applied either PF or Fertility, located at Fayetteville.
seven days POF tended to produce the E-mail for Dr. Slaton: [email protected].
greatest overall yields at sites exhibiting a
Potassium Fertilization of Russet... (continued from page 9)
potato production in Idaho should be
increased over what was previously
considered adequate, particularly on
coarse, sandy textured soils. Growers
using the information from this study
should be able to successfully manage
the K needs of Russet Burbank potato
production in Idaho.
Dr. Westermann is a Soil Scientist, USDA-ARS,
Kimberly, Idaho. Dr. Tindall is Agronomist for
J.R. Simplot Company, Pocatello, formerly
Extension Soil Specialist, University of Idaho,
Twin Falls.
12
Recent Idaho research indicates need for
increased K application for higher potential
yields of Russet Burbank potatoes.
Better Crops/Vol. 82 (1998, No. 2)