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United States Department of Agriculture

Agricultural Research Service

Research Project: INTEGRATION OF CLIMATE VARIABILITY AND FORECASTS INTO RISK-BASED MANAGEMENT TOOLS FOR AGRICULTURE PRODUCTION AND RESOURCE CONSERVATION

Location: Agroclimate and Natural Resources Research

Title: Variable environment and market affects optimal nitrogen management in wheat and cattle production systems)

Author
item Zhang, Xunchang
item Mackown, Charles
item Garbrecht, Jurgen
item Zhang, Hailin
item Edwards, Jeff

Submitted to: Agronomy Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/30/2011
Publication Date: 6/1/2012
Citation: Zhang, X.J., Mackown, C.T., Zhang, H., Edwards, J.T., Garbrecht, J.D. 2012. Variable environment and market affects optimal nitrogen management in wheat and cattle production systems. Agronomy Journal. 104(4):1136-1148.

Interpretive Summary: On average, about 33% of applied fertilizer nitrogen (N) is used by plant for grain production worldwide, and a 1% increase in N use (say from 33% to 34%) could annually save producers 200-400 million dollars worldwide. The N use efficiency can be improved by using computer simulation models to optimize N management. We used a computer simulation model to develop economically optimal N management for wheat (Triticum aestivum L.) and cattle (Bos taurus L.) production for selected climate, soil moisture, and market conditions for the north-central region of Oklahoma. For grain-only wheat, simulation results showed there was a 55% chance that optimal fertilizer N was < 40 kg ha-1 when precipitation during August-February is < 0.3 m, while there was a 90% chance that optimal fertilizer was between 90 and 120 kg ha-1 when precipitation is > 0.4 m. This result strongly supports a split N application strategy with < 45 kg ha-1 applied pre-plant and additional N top dressed in February according to precipitation and grain yield potential. For dual purpose wheat with wet soil at planting, about 20, 60, 80, and 90 kg ha-1 of pre-plant N were needed to maximize live weight gain for stocking densities of 1, 2, 2.5, and 3 heads ha-1, respectively. Net economic returns from wheat and cattle production were maximized at an N rate of 120 kg ha-1. These findings should be useful to farmers to make better decision on N rates based on soil moisture at planting, rainfall amount before February, planned stocking rate, and anticipated seasonal climate.

Technical Abstract: The average efficiency of fertilizer nitrogen (N) in grain production of cereals is about 33% worldwide, and a 1% increase in fertilizer N use efficiency (NUE) could annually save US producers 200-400 million US dollars. Process-based crop simulation models provide a unique opportunity to improve fertilizer NUE by optimizing N and synchronizing N supply with crop demand. We used a computer simulation approach to develop economically optimal N management for wheat (Triticum aestivum L.) and cattle (Bos taurus L.) production for wet, average, and dry years, two initial soil water reserves, and three market conditions. A wheat grazing model was used to optimize fertilizer N for each scenario using optimal planting dates, grazing initiation dates, and stocking densities for the north-central region of Oklahoma, USA. Based on simulated optimal N fertilizer distributions for grain-only wheat, there was a 55% chance that optimal fertilizer N was < 40 kg ha-1 when precipitation during August-February is < 30 cm, while there was a 90% chance that optimal fertilizer was between 90 and 120 kg ha-1 when precipitation is > 40 cm. This result strongly supports a split N application strategy with < 45 kg ha-1 applied pre-plant and additional N top dressed in February according to precipitation and grain yield potential. For dual-purpose wheat (forage + grain) production and an initially wet soil profile, about 20, 60, 80, and 90 kg ha-1 of pre-plant N were needed to maximize live weight gain for stocking densities of 1, 2, 2.5, and 3 heads ha-1, respectively, and about 120 kg N ha-1 to maximize total net economic returns. The yield response to N supply (fertilizer N plus soil residual inorganic N) was adequately simulated in the range of 0-170 kg N ha-1 for grain-only wheat and 0-210 kg N ha-1 for dual-purpose wheat. Overall, the wheat grazing simulation model effectively optimized fertilizer N management for wheat-based enterprises within the aforementioned scenarios for regions with similar physiography and climate as north-central Oklahoma, USA.

Last Modified: 8/24/2016
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