Integrating Field Experiments On Crop Water Deficits with Crop Modeling.

Crop production systems in the semi-arid Great Plains are normally limited by available water. Further, irrigated agriculture is increasingly competing with urban demands for water, and considerable interest is developing in how best to manage limited water for agricultural use. Addressing these issues is difficult because 1) rigorous examination of crop responses to water deficits (both amount and timing) is limited under field conditions, and 2) plant responses vary among crops and within crops (i.e., genotypes). These difficulties have slowed progress on integrating advances in molecular biology, breeding, and whole plant physiology, and quantification and incorporation into crop models has been even slower. This paper presents results for the first year of several experiments examining water deficits precisely managed in the field using drip irrigation systems. Genotype responses for several important traits (e.g., tillering and tiller retention, above-ground biomass, plant height, yield, and end-use quality) to varying water deficits (timing and amount), and gene expression across an environmental gradient, will be presented. The suitability of crop models for assessing the phenotypic plasticity, or genotype by environment interaction, to varying water deficits will be examined.