YIELD AND QUALITY OF SOYBEAN FORAGE AS AFFECTED BY CULTIVAR AND MANAGEMENT-PRACTICES

Soybean [Glycine mar (L.) Merr.] has potential for use as an alternative forage crop, however, little is known about the effects of cultural practices on forage yield and quality. A study was conducted to evaluate the effects of cultivar, row spacing, plant density, and harvest maturity on the yield and quality of soybean forage. The study was conducted at the Univ. of Wisconsin Arlington Agricultural Research Station, Arlington, WI on a Plano silt-loam soil (fine-silty, mixed, mesic, Typic Argiudoll) in 1987 and 1989. The cultivars Corsoy 79, Pella, and Williams 82 were grown at 20- and 76-cm row spacings at planting rates of 280 000 and 890 000 seeds ha-1 and were harvested al the R1, R3, R5, and R7 stages of development. Harvest maturity had the greatest effect on soybean forage yield and quality of the management practices evaluated. The yield of soybean forage increased from 2.4 Mg ha-1 when harvested at R1 to 7.4 Mg ha-1 when harvested at R7, but quality declined between stages R1 and R5 then increased from R5 to R7 as pods developed and seeds filled. Late maturing cultivars (Maturity Group III vs. Maturity Group II) produced greater forage yields but lower quality forage when harvested at the same stage of development. The 20-cm row spacing produced 1.2 Mg ha-1 more forage than the 76-cm row spacing, but crude protein concentration was 8 g kg-1 less. The results of this experiment indicate that soybean can produce forage similar in quality to alfalfa and that management practices typically used for grain production are suitable for forage production.