Modeling Winter Cereal Grain Canopies for Legume Intercrop Establishment.

As energy demands continue to increase and wheat (Triticum aestivum L.) prices remain high, more North Central U.S. corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] producers may convert some production acres to wheat. Including a winter cereal grain in the rotation increases the opportunity for incorporating a red clover (Trifolium pratense L.) or alfalfa (Medicago sativa L.) intercrop. Legume intercrops may improve soil quality, reduce erosion and weed pressure, and provide additional returns to the producer as a forage and nitrogen source. To maximize these benefits, uniform legume establishment and survival during cereal growth are critical. Red clover and alfalfa plant densities measured in mid-May at maximum legume emergence and again in mid-July at cereal grain harvest decreased 18 to 52%. We hypothesize that the most critical factor affecting legume survival is light transmittance. The influences of plant height, leaf area index, and transmission of photosynthetically active radiation of six winter wheat and triticale (X Triticosecale Wittmack) varieties on legume establishment were modeled. Model results may identify superior winter cereal grain varieties for producers to use in intercrop systems and provide plant breeders with specific canopy traits to select for in their breeding lines.