Irrigation and Planting Date Effects on Seed Yield and Agronomic Traits of Early-Maturing Soybean

Soybean [Glycine max (L.) Merr.] growers in the mid-south United States have increasingly practiced early planting and double-cropping systems. Information on crop management is desired by soybean growers to improve production and profitability. Effects of irrigation and planting date on seed yield and other agronomic traits were investigated in soybean cultivars from eight maturity groups (MG) in 2002 and 2003 at two locations in Arkansas. The planting date (April, May, and June) and irrigation treatments significantly affected seed yield, plant height, and maturity. Significant effects were also observed for number of nodes, number of pods, and number of seeds per plant, whereas number of branches per plant was not affected by planting date and irrigation treatments. Irrigation improved seed yield by an average of 83% (986 kg/ha) in all experiments conducted across two years. Highest seed yield was achieved when soybeans were planted in May, followed by April and then by June planting. The MG V and VI cultivars, conventionally grown in Arkansas, produced higher seed yields than other maturity groups and were the most suitable cultivar selections when considering seed yield alone. Significant interactions were observed among planting date, irrigation, and maturity groups/genotypes. The MG IV was a better candidate for the double-cropping system (June-planting) because of its earlier maturity and high seed yield. For the early soybean production system (April-planting), MG I and II cultivars were potentially good selections because of their short growing periods and acceptable seed yields. The various planting dates and irrigation systems combined with proper cultivar selections provide soybean producers with more options for using the land and water efficiently.