Submitted to: American Society of Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: April 30, 2007
Publication Date: November 4, 2007
Citation: Grabber, J.H. 2007. Sorghum-sudangrass yield responses to nitrogen fertilizer following legume and nonlegume forages [abstract]. In: American Society of Agronomy Abstracts. American Society of Agronomy Annual Meeting, November 4-8, 2007, New Orleans, Louisiana. 2007 CDROM. Technical Abstract: Rotation effects on the yield and N response of sorghum-sudangrass have not been reported. In this study, sorghum-sudangrass was grown in southern Wisconsin on a silt-loam soil for two years following one full production year of legume (alfalfa or birdsfoot trefoil) or nonlegume (reed canarygrass or kale) forage crops. Each year, sorghum-sudangrass was conventionally or no-till seeded in late May and harvested twice with 0 to 220 kg/ha of N fertilizer applied per harvest. Pronounced N rotation, non-N rotation, and tillage effects on sorghum sudangrass yields were observed at all harvests. Without N fertilizer, sorghum-sudangrass yields were greater following legumes than nonlegumes and yield differences were more pronounced each year in the first harvest (5.0 vs. 1.9 Mg/ha) than in the second harvest (3.3 vs. 1.6 Mg/ha). With no N fertilizer, yields both years with conventional tillage exceeded no-till (4.3 vs. 2.8 Mg/ha) in the first harvest but no differences due to tillage were observed in the second harvest. Responses to N fertilizer were generally greater with no-till and following nonlegume forages and N response progressively increased with each succeeding harvest. At each harvest, applying ~150 kg/ha of N fertilizer following forage legumes gave maximal yields (ranging from 6 to 11.5 Mg/ha). Maximal yields following non-legumes were often lower (ranging from 5 to 10 Mg/ha) and usually required higher N fertilizer applications.