Nutrient Content of Silages Made from Whole-Plant Soybeans

Abstract

Whole-plant soybean forages were chopped and ensiled in 1988 and 1989 from plots ina 2×3×2 factorial arrangement of a randomized complete block design. Maturity group IV (‘Stafford’) vs group V (‘Bay’) soybean forages were harvested and ensiled at either full bloom (R2), full pod (R4), or full seed (R6) growth stages, with (I) or without (NI) a silage inoculant for a minimum of 60 d in lined 19-L containers. Dry matter yield of Bay in both years and Stafford in 1989 increased (P<.05) with advancing growth stage, and R2 and R6 Bay yields were greater (P<.05) than R2 and R6 Stafford yields. Three-way interactions were detected (P<.05) for silage pH; total volatile fatty acids (VFA); and molar proportions of acetic, isobutyric, and butyric acids in 1988 and of acetic and butyric acids in 1989. Silages harvested at R6 had the highest (P<.0S) lactic acid and lowest (P<.05) ammonia concentrations in 1988 and the lowest (P<.05) total VFA in 1989. Bay had greater ethanol and ADL and lower N concentrations in both years (P<.05) and lower pH, ammonia, and total VFA and higher NDF and ADF in 1989 than Stafford (P<.05). Inoculated silages had lower (Ρ<·01) molar proportions of propionate in 1988 and higher (P<.01) total VFA in 1989 than NI. Silages harvested at R2 had higher N in 1988 and lower ADL in both years than those harvested at R4 and R6 (P<.05). Neutral-detergent fiber content at R4 was higher (P<.05) than at R2 and R6 in 1988 and higher (Ρ<·05) than at R2 in 1989·Considering the relative magnitude of changes in yield and quality with advancing maturity, one should delay harvesting soybeans for silage until the R6 growth stage, if possible.