Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract only
Publication Acceptance Date: 11/1/2006
Publication Date: 12/1/2006
Citation: Pan, W.L., William Schillinger, David Huggins, Richard Koenig, and John Burns. 2006. Fifty Years of Predicting Wheat Nitrogen Requirements Based on Soil Water, Yield, Protein and Nitrogen Efficiencies. In Annual meetings abstracts [CD-ROM]. ASA, CSSA, and SSSA, Madison, WI. Interpretive Summary:
Technical Abstract: During the early 1950’s synthetic N fertilizers were gaining widespread adoption in the wheat growing region of the inland Pacfic Northwestern U.S. Agronomists quickly recognized water and N as the two principal determinants of grain yield and quality Numerous N fertility trials across a range of climatic environments, soils and cropping systems provided the basis for estimating wheat yield potentials from root zone soil moisture, and N fertilizer recommendations were made from yield-based crop N requirements, estimates of soil N supplies and N use efficiencies. This N recommendation model based on the regional variations in crop-soil N budgets has stood the test of time for nearly 50 years, as confirmed by recent N fertility and agronomic trials. A recent data analysis of yield-water relationships reveals a remarkably similar slope but different y-intercept defining the lowest available water levels at which grain yields are obtainable. Spring soil moisture remains a reasonable predictor in this Mediterranean climate, but variable in-season rainfall is still a major source of error. Adjustments in the N recommendation model have been made to accommodate genetic, soil, management and climatic variables affecting water and N use efficiencies. However, limits in our ability to extrapolate the regional model to site specific applications are restricted by our ability to predict landscape processes that control the water-yield and the yield-nitrogen use relationships defining the unit N requirement. The generalized 50% single season N uptake efficiency used in the model is adjustable with improved N management, but much higher rotational N uptake efficiencies need to be recognized and taken into account.