Effects of soil moisture on the success of soil-applied inocula for soybeans

Abstract

A field trial was carried out on three sites on black soil comparing seed inoculation of soybeans with soil application of inoculum. Inoculum was applied into the furrow as a peat inoculum in a water suspension at three levels of application (80, 250, 500 l ha-1) or carried on treated alkythene granules. The soil moisture at planting varied between sites. Seed inoculation gave a consistently high level of nodulated plants (c. 70%) and treated alkythene granules consistently low (c. 50%) at all sites. Nodulation results from the water suspension depended on the level of water applied and the planting moisture. At the low moisture site only high volume application (500 l ha-1) produced satisfactory nodulation of 63%. Evidently, the tolerance of peat cultures to moisture stress is reduced by suspension in water before application to soil. The efficiency of the solid inoculant method could probably be improved by increasing the number of inoculum loci through decreased granule size.