Evapotranspiration and Soil Water Balance for Corn in a Perennial Living Mulch.

Kura clover (Trifolium ambiguum M. Bieb.) living mulch has the potential to significantly reduce nitrogen fertilizer use, nitrate leaching, and soil erosion in corn (Zea mays L.) fields of the north central U.S.  This cropping system is especially well suited for stover harvest whether for livestock feed or bioenergy feedstock.  A primary limitation of the living mulch system is the risk of water stress.  The objectives of this research are to quantify the soil water balance for rain-fed corn grown in a perennial kura clover living mulch and to find management strategies to reduce the risk of water stress on the corn in such a system.  Evapotranspiration (ET) modeling and time domain reflectometry profile water storage measurements were used to compare the water balance for the living mulch system and for conventional corn production.  Modeling was based on the FAO-56 method modified for a living mulch cropping system.  The soil water storage data confirmed the accuracy of the ET model.  In a dry season, six month ET totals were similar with and without the living mulch, but June through July ET (and hence corn yield) was reduced ~16% in the living mulch.  The corn in the living mulch experienced greater water stress, yet at maximum depletion the soil was wetter under the living mulch than the conventional corn.  This suggests reduced corn root development.  Ongoing greenhouse and field studies are testing alternative methods for suppressing springtime ET and enhancing corn root development in the living mulch.