132-5 Predicting Risk of Reducing Nitrogen Fertilization Using Hierarchical Models and On-Farm Evaluation Data.

See more from this Division: S04 Soil Fertility & Plant Nutrition
See more from this Session: Nitrogen Management to Improve Use Efficiency and Crop Yield
Monday, October 22, 2012: 2:05 PM
Duke Energy Convention Center, Room 208, Level 2
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Peter Kyveryga1, Petrutza C. Caragea2, Mark Kaiser2 and Tracy M. Blackmer1, (1)On-Farm Network, Iowa Soybean Association, Ankeny, IA
(2)Department of Statistics, Iowas State University, Ames, IA
Current nitrogen (N) fertilizer recommendation systems for corn (Zea mays L.) do not consider factors that influence yield responses to N at different levels and the uncertainty in N recommendations. We used hierarchical modeling (HM) and Bayesian statistics to quantify the risk from reducing N applications in corn based on observations from on-farm evaluations trials. Across Iowa, farmers conducted 34 trials in 2006 and 22 trials in 2007. Each trial had a normal N rate alternating with a reduced N rate (about one third less) in >3 replications, and yield losses (YL) from reduced N were calculated at 35-m intervals. Posterior distributions were used to identify field and within-field level factors affecting YL, and to quantify the risk of economic YL from reduced N in unobserved fields. In 2006 (dry May and June), the economic YL for corn after soybean (C-S) was predicted >20% than for corn after corn. Also in 2006, C-S fields with above normal June rainfall had economic YL by 35% less than those with below normal June rainfall, and sidedress N applications were about 20% more riskier than spring applications. In 2007 for C-S, N reductions with above normal spring rainfall were more riskier than with below normal, and within-fields areas with higher SOM had economic YL by about 20% less than those with lower SOM. Many on-farm evaluation trials can conducted across the state to quantify the risk from reducing N and identifying management, weather, and soil factors that affect this risk at different levels.
See more from this Division: S04 Soil Fertility & Plant Nutrition
See more from this Session: Nitrogen Management to Improve Use Efficiency and Crop Yield