System analysis of plant traits to increase grain yield on limited water supplies

Crop growth in commercial situations usually requires maximizing grain yield on limited available water resources, which results in maximizing the ratio of yield to evapotranspiration. A system analysis was undertaken to identify those plant traits that might be altered to improve crop yield in a water-limited environment. A mechanistic crop model was used to simulate maize (Zea mays L.) yield over 20 yr at Columbia, MO, which had high interannual variability in precipitation. Because sorghum [Sorghum bicolor (L.) Moench] is known to be better adapted to drier environments, a number of individual plant traits were adjusted in the maize model to represent a sorghum crop. For the tested environments, it was found that decreasing leaf size and increasing seed growth rate both resulted in decreased yield and a decreased ratio of grain yield to evapotranspiration. On the other hand, increasing the depth of water extraction resulted in increased yields and an increased ratio of grain yield to evapotranspiration. Combining sorghum-like traits in the maize model also increased yield and the ratio of grain yield to evapotranspiration when averaged for all years. For all seasons where simulated yield was less than approximately 550 g m−2, grain yields were greater for a crop with sorghum-like traits than for a crop with maize traits.