Dairy effluent effects on herbage yield and nutritive value of forage cropping systems

The utilization of dairy waste effluent provides nutrients and water for crop growth and allows producers to comply with regulations governing on-farm recycling of nutrients. Dry matter (DM) yield and nutritive value were measured for forages from five year-round cropping systems at effluent N rates of 450, 675, and 900 kg ha(-1) yr(-1) during 4 yr on a Kershaw fine sand (coated, thermic Typic Quartzipsamments) in northern Florida. Cropping systems were rye (Secale cereale L.) grown in tandem with either bermudagrass (Cynodon spp.), corn (Zea mays L.)-bermudagrass (CBR), corn-forage sorghum [Sorghum bicolor (L.) Moench; CSR], rhizoma peanut (Arachis glabrata Benth.; PR), or corn-rhizoma peanut (CPR). Annual yields increased with N level in Years 1 and 2, but not during Years 3 and 4. Yields were similar among BR, CBR, and CSR (25.9 Mg ha(-1)) in Year 1. In Year 2, BR (31.2 Mg ha(-1)) had the greatest yield followed by CBR and CSR (avg. 25.5 Mg ha(-1)). In Years 3 and 4, yields of BR (21.1 Mg ha(-1)) and CBR (20.7 Mg ha(-1)) declined while yield of CSR remained constant. Systems CPR and PR yielded less during the 4 yr (17.6 Mg ha(-1)). In vitro digestibility of BR (580 g kg(-1)) was lower than for the other systems (mean of 653 g kg(-1)). Cropping system had a major impact on forage yield and nutritive value, but N rates above 450 kg ha(-1) had relatively little effect on these responses.