Doublecropping Seed and Forage Crops with Small Grains in the Upper Midwest

Sequential doublecropping is a standard agronomic practice in the Southeast and Southern Plains of the USA. Soybean [Glycine max (L.) M err.] and grain sorghum [Sorghum bicolor (L.)] are the seed crops most frequently doublecropped following small grain. Yields have been variable in the Upper Midwest, even when the small grain is removed for forage rather than harvested for grain. This irrigated experiment was conducted in northeast Nebraska at 42° N and 97° W to evaluate doublecropping of several early maturing seed crops and summer annual forages after removal of barley (Hordeum vulgare L. ‘Hazen’) forage (first date) or winter wheat (Triticum aestivum L. ‘Cody’) for grain (second date). The seed crops used were buckwheat (Fagopyrum esculentum Moench ‘Mancan’), dwarf corn (Zea mays L. ‘Cargill 1077’), ‘DK-18’ grain sorghum, proso millet [Panicum miliaceum (L.) ‘Rise’], ‘Elgin’ soybean, sunflower (Helianthus annus L. ‘Sunwheat 101’), and rapeseed (Brassica campestris L. ‘Tobin’). Forage crops evaluated were foxtail millet [Setaria italica (L.) Beauv. ‘Snofox’], pearl millet, [Pennisetum americanum (L.) ‘NK Millex 24’], ‘Cargill Morcane’ forage sorghum, ‘Cargill Sweet Sioux V’ sorgho-sudangrass, and turnip (Brassica rapa L. ‘Purpletop Globe’). With 23 June the first date of planting, dwarf corn, grain sorghum, and soybean yielded 179, 446, and 188% more grain, respectively, than with the later 7 July average planting date. Rapeseed produced low seed yield with either planting date. Buckwheat yield with the first date was 57% of the late date yield, due to herbicide injury. Pest control problems limited firm conclusions about the suitability of sunflower and proso millet for doublecropping. None of the grain doublecrops showed more promise than soybean or grain sorghum. Among forage crops, pearl millet, forage sorghum, and sorghum sudangrass forage yields were 115, 102, and 117% respectively, with the early vs. late planting dates. Forage sorghum produced the highest forage, digestible dry matter, and protein yields. First date of planting yields of foxtail millet and turnip were 91 and 76% compared with later planting; herbicide injury reduced first planting date turnip root yield 1 yr.