Nitrogen fixation (15N dilution) with soybeans under Thai field conditions

Abstract

Field experiments were conducted in northern Thailand to evaluate the effect of five herbicides and three watering schedules on soybean yields and Nz fixation. The herbicides sethoxydim, alachlor, fluazifop butyl and metolachlor when added at recommended rates for weed control did not result in detrimental effects on seed yields or benefits of N2 fixation. Paraquat additions significantly reduced the amount of N2 fixed as measured by ~SN dilution methods. Inoculation of the soil with a mixed strain inoculum of Bradyrhizobium japonicum increased seed yields and measurements of Nz fixation. The application of water to soybeans only when water stress symptoms such as wilting were observed resulted in drastic reductions in both yield and N 2 fixation of four cultivars of soybeans. Reducing the water application from weekly to biweekly did not seriously reduce yields or N2 fixation benefits.

Nitrogen fixation(N-15 dilution) with soybeans under Thai field conditions. III. Effects of Bradyrhizobium japonicum strains and herbicides in northeast Thailand.

“…RENNIE et al (13) inoculated soybeans with a granular product (Soil Implant, Nitragin Co.). KUCEY et al (3) showed that one of the strains used in the granular inoculant (61 A 101 C) was not as effective as other strains used for soybean yields and N2 fixation in soils of northern and central Thailand. Research is needed to determine whether substitution of selected strains into a commercial inoculant such as Soil Implant could result in yet greater levels of N2 fixation than are currently obtained.…”

“…Merr.) is beneficial in the tropical soils of southeast Asia (1)(2)(3). The benefits depend greatly on the selection of appropriate bacterial strains, since bacterial strain-soybean cultivar specificity has been found in many cases (3)(4)(5)(6).…”

“…is beneficial in the tropical soils of southeast Asia (1)(2)(3). The benefits depend greatly on the selection of appropriate bacterial strains, since bacterial strain-soybean cultivar specificity has been found in many cases (3)(4)(5)(6). Native populations of Bradyrhizobium japonicum cannot be relied upon to supply adequate amounts of N for commercial soybean production since they vary considerably in their competitiveness and N2-fixing abilities (7,8).…”

Nitrogen fertilization and use efficiency in an intercrop system of cassava (Manihot esculenta Crantz) and soybean (Glycine max (L) Meril.)

“…Conflicting results of nitrogen application to soybean have been reported from response to no response of which no conclusion on the amount of fertilization at intercropping system can be drawn (Mengel et al, 1987). Affipunguh (1991) determined the safe levels of supplementary nitrogen in maize/cowpea intercrop to be 50 kg N/ha -1 , while Kucey (1988) reported that nitrogen fixation in soybean ranged from 32 to 161 kg N/ha -1 annually. This study was therefore conducted to determine the effects of intercropping cassava with soybean on tuber and grain yields of the two crops, respectively and on nitrogen use efficiency (NUE) of cassava at the intercropping system.…”