Planting date effects on yield and quality of foxtail millet and three annual legumes

Abstract

Annual grasses and legumes offer potential as forages in the northern Great Plains region of the USA during late summer when perennial cool-season grass pastures are unproductive. The objective of this study was to evaluate the forage yield, in vitro digestible dry matter (IVDDM), and crude protein concentration of four annual species planted in May, June, and July at two South Dakota locations in 1989 and 1990. The species evaluated were cowpea (Vigna unguiculata (L.) Walp.), mungbean (Vigna radiata (L.) Wilczek), soybean (Glycine max (L.) Merr.), and Siberian foxtail millet (Setaria italica (L.) Beauv.). In 1989 cowpea, soybean, and millet produced similar yields at Highmore when planted in May, whereas in 1990 soybean had the highest forage yield of 8.3 t ha−1. Forage yields for the July planting were lower than those of the May planting, except for mungbean grown at Highmore in 1989 where the July planting produced 2.2 t ha−1 more forage than the May planting. Cowpea had significantly greater IVDDM than the other species for all three planting dates at Beresford in 1989, whereas at Highmore IVDDM for cowpea was not greater than that of mungbean for the May and June planting dates. Cowpea had the greatest crude protein concentration for all planting dates at Highmore in 1989, the greatest crude protein concentration for May and June planting dates at Beresford, and similar crude protein concentration to soybean for the July planting date. Millet, with the exception of the May planting at Highmore in 1990, consistently had lower IVDDM and crude protein concentrations than all three legumes each year at each location. The highest soybean forage yields at each location were always obtained from the May plantings. Cowpea forage yields were highest for the May planting at Highmore in 1989 and the June planting in 1990. Since cowpea often had higher forage yields, IVDDM, and crude protein concentrations than the other species it appears to be a viable alternative forage crop for this region.Key words: Annual forage legumes, millet, yield, quality