Year-to-Year and Maturity Variation in Rainfed Soybean Yield by Planting Dates

The interactions on rainfed soybean yield among planting date,maturity,and year-to-year climate change were studied using CROPGRO-soybeanmodel.Simulations were based on 19 planting dates,maturity groupsⅢ,Ⅳ and V,30 years recorded weather data from Corbin,Suffolk,West Point in Virginia,USA.Yield was similar on early plantings and went down with late plantings.Both grand and year-to-year variation of soybean yield declined linearly with planting date.Year-to-year climate variation was dominant yield variation source in rainfed soybean production.Interaction occurred between planting date and maturity.Optimal planting dates for different sites lied within 130th-170th day of a year.Irrigation is recommended for profitable crops,especially in Corbin and West Point.