Dry matter accumulation and forage quality characteristics of different soybean genotypes
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Three different soybean [Glycine max (L.) Merr.] cultivars (A-3127, Derry, and Yemsoy) were evaluated for dry matter (DM) yield, plant components, and crop growth rate (CGR) at different row spacings and harvesting stages in 3 locations with Mediterranean-type climate in a split-split plot design with 3 replications in 2009 and 2010. In addition, crude protein (CP), crude protein yield (CPY), acid detergent fiber (ADF), neutral detergent fiber (NDF), total digestible nutrients (TDN), and relative feed value (RFV) of harvested forage soybeans were determined at the Bursa (Turkey) location. Increased row spacings significantly reduced DM yield at all locations. Combined over other main effects, the 25-cm row spacing produced 35% more DM yield than the 75-cm row spacing. Row spacings greatly affected DM yield at the R5 and particularly the R7 stage, but this effect was minimal at the RI stage. The forage-type cultivar Derry produced significantly higher DM yield in all locations, particularly at the R5 and R7 stages. The constituent components of DM were similar at different row spacings of soybean cultivars. In general, the CGR decreased from 25-cm row spacing to 75-cm row spacing in all locations, and the CGR of the cultivars varied significantly according to harvest period, row spacing, and location. Derry had a significantly higher CGR than the other cultivars in the Antalya and Bursa locations. Quality characteristics of soybean forage were not 'significantly affected by row spacing and showed little effect by cultivar. Harvest stage significantly affected CP, ADF, NDF, TDN, and RFV concentrations of soybean forage. It was concluded that in Mediterranean environments forage-type soybeans (i.e. Derry) can be seeded in narrow rows (25 cm) at high plant population (100 kg ha(-1)) and offer the most DM yield when harvested at later R stages (e.g., R7) rather than at the early reproductive stage.