Forage Yield and Nutrient Uptake of Warm‐Season Annual Grasses in a Swine Effluent Spray Field

Abstract

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.