Abstract
Accurate fertilizer N recommendations for irrigated continuous corn ( Zea mays L.) production in the Great Plains are important for maximizing productivity and profit, while minimizing environmental impact of fertilizer use. The objectives of this study were to determine the effects of long‐term N and P fertilization on grain yield and fertilizer recovery by irrigated continuous corn and to compare predicted N recommendations with actual N requirements. Six rates of N (0, 40, 80, 120, 160, and 200 lb/acre) and two rates of P (0 and 18 lb P/acre) in a factorial arrangement were applied annually from 1961 to 1991 on a Ulysses silt loam (fine silty, mixed, mesic Aridic Haplustoll) near Tribune, KS. Grain yields were greater with a combination of N and P than with either applied alone. The optimal N rate was about 160 lb N/acre and was relatively constant over time. Averaged over the last 10 yr, application of 160 lb N/acre increased grain yields 46% without P and 103% with P. The yield benefit from applied P has increased over time. With adequate N, P increased grain yields by 29% averaged over 31 yr and 48% over the last 10 yr. Phosphorus fertilization reduced grain moisture from 28 to 23%. Apparent fertilizer N recovery in the grain at 160 lb N/acre was twice as high with P as without P. A N recommendation model was used to compare estimated N requirements with actual N rates required to meet yield goals. Yields obtained with 160 lb N/acre were estimated to require 220 to 260 lb N/acre, or an overestimation of 30 to 60%. These data suggest that the crop factor used in the model may need to be reduced to improve accuracy of N recommendations. Research Question Long term fertilizer use is a common practice for irrigated continuous corn in the Great Plains. Accurately identifying the fertilizer N requirement is important for maximizing productivity and profit, while minimizing environmental impact of fertilizer use. This study quantified the effect of repeated fertilizer applications on optimal N rate and evaluated the accuracy of predicting N requirements using a N recommendation model. Literature Summary Several studies have shown that accurately identifying the optimal N rate is an important N management decision for maximizing fertilizer N recovery by the crop, minimizing residual fertilizer N after harvest, and reducing potential groundwater contamination. Establishing yield goals that are too high or not taking into account residual soil N can result in overestimating N requirements. Adequate amounts of other plant nutrients also are required to maximize fertilizer N recovery. Study Description Six rates of N fertilizer (0, 40, 80, 120, 160, and 200 lb N/acre) and two rates of P (0 and 18 lb P/acre) were applied annually (1961–1991) to irrigated continuous corn on a Ulysses silt loam. Measurements included grain yield, grain N and P, grain moisture, and apparent fertilizer recovery. Applied Question What is the optimum N rate for irrigated continuous corn? In this long‐term study, the optimum N rate was about 160 lb N/acre and was relatively constant across years (Table ). Although fertilizer P was needed to maximize grain yield, it had little effect on optimal N rate. What effect does P have on fertilizer N efficiency and grain production? With optimal N, fertilizer P doubled apparent N fertilizer recovery. Fertilizer P decreased grain moisture and increased grain yields by 48% averaged over 10 yr when applied with optimal N. Do current N recommendation models accurately predict N requirements? No. In 2 yr of the study with average or above average yields, the model overpredicted N needs by 30 to 60% compared with observed optimal N rate. Grain yield response of corn to N and P. 1982–1991 1961–1991 N rate −P +P −P + P lb/acre ‐‐‐‐‐‐‐‐‐‐‐‐bu/acre‐‐‐‐‐‐‐‐‐‐‐‐‐ 0 82 87 70 73 40 109 131 107 119 80 115 150 121 143 120 114 166 124 159 160 120 177 131 169 200 119 173 132 166
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Claims 13
Claim · model-written summary
A combination of N and P gave greater grain yields than either N or P applied alone.
- Treatment
- combination of N and Pe1
- Outcome
- grain yieldse1
- Direction
- greatere1
- Comparator
- either applied alonee1
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“irrigated continuous corn ( Zea mays L.) production”
e1“Grain yields were greater with a combination of N and P than with either applied alone.”
Claim · model-written summary
The optimal N rate for irrigated continuous corn was about 160 lb N/acre.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“irrigated continuous corn ( Zea mays L.) production”
e2“The optimal N rate was about 160 lb N/acre and was relatively constant over time.”
Claim · model-written summary
The optimal N rate was relatively constant over time.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“irrigated continuous corn ( Zea mays L.) production”
e2“The optimal N rate was about 160 lb N/acre and was relatively constant over time.”
Claim · model-written summary
Application of 160 lb N/acre increased grain yields by 46% without P over the last 10 yr.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“irrigated continuous corn ( Zea mays L.) production”
e3“Averaged over the last 10 yr, application of 160 lb N/acre increased grain yields 46% without P and 103% with P.”
Claim · model-written summary
Application of 160 lb N/acre increased grain yields by 103% with P over the last 10 yr.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“irrigated continuous corn ( Zea mays L.) production”
e3“Averaged over the last 10 yr, application of 160 lb N/acre increased grain yields 46% without P and 103% with P.”
Claim · model-written summary
With adequate N, P increased grain yields by 29% averaged over 31 yr.
- Treatment
- With adequate N, Pe4
- Outcome
- grain yieldse4
- Direction
- increasede4
- Value
- 29%e4
- Qualifier
- averaged over 31 yre4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“irrigated continuous corn ( Zea mays L.) production”
e4“With adequate N, P increased grain yields by 29% averaged over 31 yr and 48% over the last 10 yr.”
Claim · model-written summary
With adequate N, P increased grain yields by 48% over the last 10 yr.
- Treatment
- With adequate N, Pe4
- Outcome
- grain yieldse4
- Direction
- increasede4
- Value
- 48%e4
- Qualifier
- over the last 10 yre4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“irrigated continuous corn ( Zea mays L.) production”
e4“With adequate N, P increased grain yields by 29% averaged over 31 yr and 48% over the last 10 yr.”
Claim · model-written summary
The yield benefit from applied P has increased over time.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“irrigated continuous corn ( Zea mays L.) production”
e5“The yield benefit from applied P has increased over time.”
Claim · model-written summary
Phosphorus fertilization reduced grain moisture from 28 to 23%.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“irrigated continuous corn ( Zea mays L.) production”
e6“Phosphorus fertilization reduced grain moisture from 28 to 23%”
Claim · model-written summary
With P, apparent N fertilizer recovery in the grain at 160 lb N/acre was twice as high as without P.
- Treatment
- with Pe7
- Outcome
- Apparent fertilizer N recovery in the graine7
- Direction
- twice as highe7
- Comparator
- without Pe7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“irrigated continuous corn ( Zea mays L.) production”
e7“Apparent fertilizer N recovery in the grain at 160 lb N/acre was twice as high with P as without P.”
Claim · model-written summary
The N recommendation model overestimated N requirements by 30 to 60% at 160 lb N/acre yield goals.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“irrigated continuous corn ( Zea mays L.) production”
e7“Yields obtained with 160 lb N/acre were estimated to require 220 to 260 lb N/acre, or an overestimation of 30 to 60%”
Claim · model-written summary
The crop factor used in the N recommendation model may need to be reduced to improve accuracy of N recommendations.
- Outcome
- crop factor used in the model may need to be reducede7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“irrigated continuous corn ( Zea mays L.) production”
e7“These data suggest that the crop factor used in the model may need to be reduced to improve accuracy of N recommendations”
Claim · model-written summary
Fertilizer P had little effect on the optimal N rate.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“irrigated continuous corn ( Zea mays L.) production”
e7“Although fertilizer P was needed to maximize grain yield, it had little effect on optimal N rate.”
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See all 2,185 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.