Submitted to: Agronomy Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/1/2004
Publication Date: 6/1/2004
Citation: Baker, D.A., Young, D.L., Huggins, D.R., Pan, W.L. 2004. Economically optimal nitrogen fertilization for yield and protein in hard red spring wheat. Agronomy Journal. 96:116-123. Interpretive Summary: The price that a producer receives for hard red spring wheat (HRSW), unlike soft white wheat (SWW), is influenced by protein content(%). Since both yield and protein percentage directly affect profit, producers may desire to apply levels of N fertilizer to HRSW that maximize profits considering both yield and protein. Unfortunately, growers often over-apply N to achieve both yield and protein goals. Yield and protein of HRSW were integrated into a profit model conditional on grain price, nitrogen fertilizer price, and price premium or discounts based on departure from 14% grain protein. Maximum profit was predicted to be achieved by fertilizing for slightly less than 14% protein for both high and low N prices. This analysis shows that producers need not target high protein % by applying high rates of nitrogen fertilizer in order to optimize profits. Lower applications of N will decrease N contamination of surface and ground waters and increase overall profits to growers.
Technical Abstract: The price that a producer receives for hard red spring wheat (HRSW), unlike soft white wheat (SWW), is influenced by protein content (%). The producer receives a premium on wheat with greater than 14% grain protein and a discount on wheat with less than 14% grain protein. Since both yield and protein percentage directly effect profit, producers may desire to apply levels of N fertilizer to HRSW that maximize profits considering both yield and protein. HRSW field experiment data consisting of rates of N fertilization (kg ha-1), grain yield (kg ha-1), and grain protein (%) were used to estimate regression relationships to predict yield and protein in response to N. The field experiments used randomized complete block designs over two growing seasons, 1987 and 1989. Experiments were located near Pullman, WA (550 mm average annual precipitation). The analysis considered high, intermediate, and low grain prices, five premium/discount (P/D) structures and high and low N prices showing their effects on optimal N fertilization. Estimated yield and protein models were integrated into a profit ($ ha-1) function conditional on grain price, N price, and P/D structure. Increasing N price at all wheat prices resulted in a decrease in optimal N levels and levels at all P/D¿s and resulted in reduced profits in each scenario. At the two lowest P/D structures associated with the least price reward for high protein, it was most profitable to fertilize for slightly less than 14% expected protein. Optimal yield varied little with changes in both N and wheat price.