ASA Southern Branch 2008 Annual Meeting
February 3-5, 2008
Dallas, TX

Sunday, February 3, 2008

Response of Determinate and Indeterminate Soybeans to Bradyrhizobium japonica Seed Inoculation on a Clay Soil Following Rice.

Paul Francis1, Dain Strickland2, and C. Robert Stark1. (1) Division of Agriculture, University of Arkansas at Monticello, SEREC-UAM, 1408 Scogins Dr., Monticello, AR 71656, (2) Crop, Soil and Environmental Sciences, University of Arkansas, 276 Altheimer Dr., Fayetteville, 72704

A flooded rice soil that remains water saturated through most the winter may impact natural populations of N-fixing bacteria for soybeans.  Seed inoculation with an improved strain of N-fixing bacteria in these situations may enhance nodulation and yield. The effects of Bradyrhizobium japonica seed treatment on the nodulation, yield, and yield components of determinate and indeterminate soybean in a clay soil following rice was investigated in a greenhouse study.  Seed of ‘DP4331’, a Group IV indeterminate, and ‘PG 5822’, a Group V determinate, were planted in pots of Sharkey clay collected from a field previously in rice and grown to R7 growth stage.  Treatments were cultivar, and inoculated (Nod +®, Becker Underwood) or untreated, surface sterilized seed.  Seed treatment and cultivar had no effects on nodule numbers per plant, nodule weight, or number of pods or seed set per plant.  Average seed weights were 11.0 and 8.7 g plant-1 respectively for the DP4331 and PG5822 and significant at the 0.05 level of probability, but most likely due to genetic differences. The lack of overall effect of seed inoculation on yield and yield components suggest that further greenhouse studies be conducted prior to consideration of field-scale research.