INFLUENCE OF SUMMER GRASS AND LEGUME CROPS ON WINTER-GROWN WHEAT AND LUPIN

This research was conducted during 1994 and 1995 on a Dothan sandy loa m (fine, loamy siliceous, thermic Plinthic Kandiudults) located at the North Florida Research and Education Center (NFREC), Quincy, N. The o bjective of this research was to evaluate the influence of summer gras s and legume crops on winter-grown wheat and lupin. Winter wheat (Trit icum aestivum L.) (var. Coker 9835) and white lupin (Lupinus albus L.) (var. ''Lunoble'') followed tropical corn (Zea ,mays L.), pearl mille t [Pennisetum glaucum (L.) R. Br., HGM(TM) 100] and soybean [Glycine m ax (L.) Merr.]. Four nitrogen rates (0, 67, 134 and 202 kg ha(-1)) wer e applied to tropical corn and pearl millet. Higher yields of wheat si lage [35% dry matter (DM)] in 1994 were obtained after tropical corn ( 14.3 t ha(-1)) and soybean (13.3 t ha(-1)) than after pearl millet (12 .9 t ha(-1)) but, in 1995, wheat silage (35% DM) yields were higher af ter soybean and pearl millet (15.3 t ha(-1) and 14.4 t ha(-1), respect ively). The N content of wheat silage in 1994 increased with previous N fertilization on rotation crops. Highest wheat grain yield (2.3 t ha (-1)) in 1994 occurred after both tropical corn and soybean. In 1995, grain yields of wheat were generally lower than in 1994 and without si gnificant effects from previous crops. The grain yield of wheat after tropical corn in 1994 was a linear function of N rate applied to tropi cal corn (0 to 202 kgN ha(-1)). The N content of wheat grain in 1994 f ollowing tropical corn was highest at 125 kg N ha(-1). Nitrogen fertil ization of previous rotation crops did not affect wheat grain yields i n 1995. The 4.4 t ha(-1) silage yield of white lupin in 1994 after soy bean was higher than after tropical corn or pearl millet. In 1995 the highest yield of lupin silage (5.2 t ha(-1)) was obtained after soybea n. In 1994, the highest grain yield (1134 kg ha(-1)) of white lupin wa s obtained after tropical corn, but in 1995 the previous-crop influenc e was not significant.