Coupling Effect of Water and Fertilizer on Soybean Yield and Nutrient Absorption

Soybean cultivar Bei 92-28 was tested in this experiment in 2000 to study the coupling effect of water and ferilizer on soybean yield.The results showed that the effect of irrigation varied among the levels of fertilizer application,and vice versa;pods per plant,seeds per pod.and 100-seed weight had positive correlations with soybean yield,but the degrees of correlations of different treatments were various;LAI and dry matter accumulation could be significantly increased when watered and applied fertilizer with different levels,but high fertilizer application treatment didn't obtain the highest yield;watering could increase the absolute absorption amount of N,P,K in seeds,but the accumulation rates were various.

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-yearclimate change were studied using CROPGRO-soybean model. Simulations were based on 19 plantingdates, maturity groupsⅢ, ⅣandⅤ, 30 years recorded weather data from Corbin, Suffolk,West Point in Virginia, USA. Yield was similar on early plantings and went down with lateplantings. Both grand and year-to-year variation of soybean yield declined linearly withplanting date. Year-to-year climate variation was dominant yield variation source inrainfed 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.

Some Aspects of Yield Physiology Research in Soybean

The paper reviews the factors and mechanisms involved in the regulation of seed growth,discusses the roles of source sink relationship in yield formation and effects of climate change and canopy photosynthesis on groth and yield in soybean.

Some Eco-Physiological Characteristics at R4-R5 Stage in Relation to Soybean Yield Differing in Maturities

Digital plant canopy imager and photosynthesis analyzer system were used to analyze thecharacteristics of canopy structure, photosynthetic physiology and micro-environmentalfactors at R4-R5 stage in different yielding soybean cultivars or lines with differentmaturities. The results showed that the common characteristics of high yielding soybeancultivars were high LAI, uniform foliage distribution in all horizontal directions, lessvariance of photosynthetic rate between top and bottom leaves in canopy and relativelyhigher photosynthetic rate of the whole canopy. All these characters combined in allresulted in higher canopy photosynthetic productivity, and pod number, seed number andseed weight per plant, especially pod and seed number in top and middle canopy wereincreased. The characters of high yielding canopy varied among maturities. Light interceptionwas more important to early cultivars. Less foliage inclination angle was benefit tointercept more solar energy during yield formation. As late soybean cultivars had a moreclosure canopy and higher LAI, greater foliage inclination angle in all layers of highyielding canopy made more solar radiation penetrate into canopy, which was beneficial toyield formation.