Double-Crop Soybean Leaf Area and Yield Responses to Mid-Atlantic Soils and Cropping Systems

Double-crop soybean (Glycine mar L.) often yields less than full-season soybean, due in part to decreased leaf area development. Information is lacking on the effect of cropping system and plant-available water holding capacity (PAWHC) as affected by soil type on LAI in field-scale environments. The objectives of this research were to (i) determine the effect of three cropping systems and three soil types that vary in PAWHC on double-crop soybean leaf area and yield; and (ii) validate the LAI-yield relationship in a field-scale experiment. Soybean LAI and yield were measured at random geographically located positions during the 1999 to 2001 cropping seasons. During years of early season or little drought stress, LAI and yield were 1.1 to 1.2 units and 480 to 558 kg ha(-1) less on the lowest PAWHC soil compared with the soil with the highest PAWHC. Soybean LAI and yield were reduced 0.4 units and 301 kg ha(-1) when soybean experience early season drought stress and was not rotated. Under conditions of late-season drought stress, LAI and yield of rotated soybean were 1.6 units and 1350 kg ha(-1) less on the lowest PAWHC soil. When soybean was not rotated and under conditions of late-season drought stress, LAI and yield were reduced by 2.9 units and 1770 kg ha(-1) for the soil with the lowest PAWHC, and 1.6 units and 760 kg ha(-1) for the soil with intermediate PAWHC. Soybean LAI was linearly related to yield only on the lowest PAWHC soil where LAI was low.