Forage yield and nutrient uptake of warm-season annual grasses in a swine effluent spray field

Five warm-season annual grasses were compared for dry matter (DM) yield and nutrient uptake alongside bermudagrass [Cynodon dactylon (L.) Pers.] on a Brooksville silty clay (fine, montmorillonitic, thermic Aquic Chromuderts) in a field that had swine (Sus scrofa) effluent applied through a center pivot sprinkler system. Annuals were browntop millet [Panicum ramosum (L.) Stapf in Prain], pearl millet [Pennisetum glaucum (L.) R. Br.], sudangrass [Sorghum bicolor (L.) Moench], sorghum-sudan, [Sorghum bicolor (L.) Moench], and crabgrass [Digitaria sanguinalis (L.) Scop.]. Grasses were tested in 3 yr (1999-2001), but results in 2000 were incomplete due to poor growing conditions. In 1999 (establishment year for bermudagrass) sorghum-sudan had the highest DM yield (18.9 Mg ha(-1)) and P uptake (50.3 kg ha(-1)). In 2001, sorghum-sudan DM yield (20.6 Mg ha(-1)) and P uptake (56.3 kg ha(-1)) were equivalent to established bermudagrass (21.3 Mg ha(-1) and 56.1 kg ha(-1), respectively). In 2001 sudangrass and pearl millet DM yields (17.4 and 15.7 Mg ha(-1), respectively) were equal to and lower than sorghum-sudan, but P uptake of pearl millet (49.5 kg ha(-1)) did not differ from sorghum-sudan, due to the high P concentration (3.2 g kg(-1)) in pearl millet. Browntop millet and crabgrass DM yields and P uptake were less than those of sorghum-sudan in both years. Sorghum-sudan and pearl millet were higher in DM yield and P uptake than the other annuals in both years, equal to established bermudagrass, and therefore should be the most useful in nutrient management hay systems in the southeastern USA.