Weather during the growing season is critical for corn and soybean yields. Adjusting for weather in an analysis of historical U.S. corn and soybean yields is important for determining underlying trends and future yield expectations. Models for U.S. corn and soybean yields provide estimates of the effects of weather on yields for those crops, allowing an analysis of those effects to be used to derive weather-adjusted trend yields. The corn model also includes planting progress by the middle of May. The estimated models indicate that reductions in precipitation below its average result in larger declines in yields than the gains in yields resulting from increases in precipitation of equal magnitudes above its average. The yield models are used to track effects of high temperatures and drought on U.S. corn and soybean yields in 2012 and to provide estimates for expected 2013 yields. Further, the models provide a framework for assessing changes in expected yields due to planting progress and weather developments. Figures and tables. This is a print on demand report.

Why model? Agricultural system models enhance and extend field research...to synthesize and examine experiment data and advance our knowledge faster, to extend current research in time to predict best management systems, and to prepare for climate-change effects on agriculture. The relevance of such models depends on their implementation. Methods of Introducing System Models into Agricultural Research is the ultimate handbook for field scientists and other model users in the proper methods of model use. Readers will learn parameter estimation, calibration, validation, and extension of experimental results to other weather conditions, soils, and climates. The proper methods are the key to realizing the great potential benefits of modeling an agricultural system. Experts cover the major models, with the synthesis of knowledge that is the hallmark of the Advances in Agricultural Systems Modeling series.