Intercropping Corn and Kura Clover: Response to Nitrogen Fertilization

Nitrogen fertilizer is an important input for corn (Zea map L.) production and leaching losses contribute to NO3-N in water systems. This study was conducted to determine whether a kura clover (Trifolium ambiguum M. Bieb.) intercropped corn system could reduce corn N fertilization need and NO3-N in the soil profile, while maintaining corn productivity. Two systems were studied at six sites in Iowa, soybean [Glycine max (L.) Merr.]-corn intercropped with established kura clover and soybean-corn without kura clover. Six N fertilizer rates were applied to corn in each system. Excessive kura clover competition caused reduced corn population, delayed development, and reduced grain yield in 2006. More vigorous kura clover growth suppression in 2007 resulted in similar yield between the kura clover and no-kura clover systems, with greater yield in the intercropped kura clover at a site with coarse-textured soil. The kura clover system did not reduce corn N fertilization requirement, as measured by response in plant N stress and grain yield. The kura clover also did not influence NO3-N in the soil profile before, during, or after the growing season. These results differ from other studies where kura clover intercropping has reduced corn N fertilization need and not reduced corn yield. Intercropping corn with kura clover posed the challenge of sufficiently suppressing the clover to allow successful corn establishment and production, and in addition did not provide potential benefits such as reduced N fertilization requirement or less NO3-N in the soil profile.