ARS | Publication request: Prohexadione-Ca improves the establishment and subsequent yield of alfalfa interseeded into silage corn

Submitted to: Proceedings of Plant Growth Regulation Society of America
Publication Type: Proceedings
Publication Acceptance Date: June 29, 2012
Publication Date: July 23, 2012
Citation: Grabber, J.H. 2012. Prohexadione-Ca improves the establishment and subsequent yield of alfalfa interseeded into silage corn [abstract]. Proceedings of Plant Growth Regulation Society of America. p 27-28.

Technical Abstract: Establishing alfalfa by interseeding into corn rather than by conventional spring-seeding after corn could double first-year yields of alfalfa, but interseeding is currently unworkable due to excessive competition between the co-planted crops. Our goal is to identify plant growth regulator (PGR) treatments that will boost successful establishment of interseeded alfalfa to >80% and limit yield depression of corn to <5%. Such a system could improve the profitability of first year alfalfa by about $170 to $290 per hectare. A screening of PGRs suggested that prohexadione-Ca might be useful for limiting excessive top growth of interseeded alfalfa during its establishment in corn. Field studies were then carried out for three years near Prairie du Sac Wisconsin to evaluate prohexadione-Ca applications on alfalfa that was planted with corn in early to mid-May. In 2009 and 2011, a mid-June drop-nozzle application of 1 kg/hectare prohexadione-Ca reduced alfalfa herbage mass by 25% by mid-July and doubled plant survival by mid-October compared to non-treated controls. In 2010, an earlier application of prohexadione-Ca had no effect on alfalfa growth and survival and all seedlings died that year due to excessive competition from corn. Alfalfa interseeding reduced silage corn yields by 9 to 15% compared to corn-only controls. Prohexadione-Ca application had no effect on corn yields. First-year yields of alfalfa established by interseeding were two-fold greater than conventionally spring-seeded alfalfa. Prior year prohexadione-Ca applications increased first year alfalfa yields by 11% compared to untreated controls. Overall, prohexadione-Ca shows promise for enhancing the establishment and subsequent yield of interseeded alfalfa, but additional studies with this and other PGRs are needed to further improve alfalfa establishment, lessen yield reductions in corn, and develop workable production systems.