Effects of Soil Moisture on Nodulation and Nitrogen Fixation

Abstract

The objectives of these studies were to evaluate the effects of soil moisture content on nodulation, nitrogen fixation, growth and yield of SJ2 soybean inoculated with Rhizobium japonicum. Two sets of experiments were conducted, the first was designed to evaluate nodulation of soybean and the second for nitrogen fixation and yield observations. These were performed by mixing the seeds with Rhizobium japonicum powder using gum Arabic as adhesive material and the inoculated seeds were planted in pots containing fertilized and limed Korat soil. The soil moisture was kept at 100% FC following with water addition at 1, 2, 3, 4, and 5 days intervals. Results of these experiments revealed that nodulation in soil with high Moisture contents were better than those of the soil with lower water contents. Addition of water at one day interval gave higher nodulation than those of the other treatments. At higher soil water contents plant growth and nitrogen fixation were relatively higher than those of soil with lower contents. Addition of water at one day interval gave batter growth, higher nitrogen fixation, and higher seed yield than those of the other treatments. It is suggested that to obtain good nodulation, nitrogen fixation, growth, and yield of soybean grown in Korat soil, moisture contents should be kept between 80 to 100% FC and water is added at 1 to 2 days intervals.