Soybean varietal response to liquid swine manure application

Applying manure to soybean [Glycine max (L,) Merr,] as a routine management practice requires additional information about cultivar-dependent response s. Our objective was to determine seed yield dry matter accumulation, N acc umulation, and lodging responses for a cross-section of adapted public and private soybean cultivars when liquid swine (Sus scrofa) manure was applied . Field studies were conducted at seven locations in southern Minnesota dur ing 1996 and 1997. Whole-plot treatments included three swine manure rates (zero, low, and high) injected with sweeps to a soil depth of 13 cm before planting, Split-plot treatments consisted of U public and private soybean c ultivars. Average seed yield for all cultivars at three of seven locations was generally positive, increasing on average 1.4 kg kg(-1) of applied avai lable N, A significant manure rate X cultivar interaction was observed for lodging scores, but increased lodging was not related to any change in yiel d. Seed yield decreased with increasing manure rates at a seventh location, where there was a history of white mold [Sclerotinia sclerotiorum (lib.) d . By.] incidence. At this location, seed yield for the control was 0.20 Mg ha(-1) greater than seed yield from either manure rate, and response to man ure application was not the same for every cultivar. Except for this latter site, seed yield response to increasing manure rate was either favorable o r innocuous, despite increased lodging. Manure application to soybean appea rs to be an acceptable management practice regardless of cultivar, except w hen the application exacerbated an already present disease pressure.