Publication Date


Degree Program

Department of Agriculture

Degree Type

Master of Science


Soybean [Glycine max (L.) Merr.] is a valuable source of edible food and organic nitrogen. Soybean cultivar development and cultural practices have been directed toward seed production rather than forage or green manure production. Recent environmental concerns have resulted in renewed interest in the use of organic matter in agriculture. The objective of the present investigation was to determine the effects of cultivar maturity differences and planting dates on biomass production of soybean. The research was conducted on the Western Kentucky University Farm in 1993. The experimental design was a split-split-plot with four replications. The three planting dates (June 2, June 16, and July 6) were main-plots, the three harvest dates were split-plots, and the five cultivars were split-split-plots. The cultivars and their maturity groupings and areas of adaptation are as follows: 'McCall' (00, Minnesota), 'A2506' (II, Iowa), 'FFR561' (V, Kentucky), 'Perrin' (VIII, South Carolina), and 'Laredo1 (undesignated maturity, forage cultivar). Each experimental unit was 45 m2. Seeds were inoculated and broadcast at the rate of 175 kg ha-1 and covered by disking. Average biomass production (oven dry basis) decreased progressively (2918, 2450, and 2088 kg ha-1) for the later planting dates. For the June 2 and June 16 planting dates, biomass yields increased for successive harvest dates; however, for the July 6 planting date, biomass yields did not differ for harvests 2 and 3. When cultivars were compared at the early bloom stage, later maturing cultivars produced more biomass. Laredo was consistently among the highest producers. There were significant interactions involving planting dates, harvest dates, and cultivars. Soybean stands and yields were reduced by inadequate seed covering, by insufficient soil moisture, especially the second planting, and by competition from johnsongrass and pigweed. However, these results indicate that soybean is a good source of green manure during the summer.


Agriculture | Agronomy and Crop Sciences