Recurrent inoculation of soybeans are not necessary
2015
Andersson, E., Swedish Univ. of Agricultural Sciences, Uppsala (Sweden). Dept.of Soil and Environment | Maartensson, A., Swedish Univ. of Agricultural Sciences, Uppsala (Sweden). Dept.of Soil and Environment | Fogelberg, F., JTI - Swedish Inst. of Agricultural and Environmental Engineering, Uppsala (Sweden)
Soybean is a legume used world-wide for food and fodder. It fixes atmospheric nitrogen and symbiotically produces high quality protein, and is therefore a valuable crop to include in any crop rotation. Currently Sweden imports large quantities of soybean, notwithstanding the negative impact on the environment, owing to, e.g., deforestation in countries where soybeans are produced and the use of long transportation routes. When cultivating soybeans on juvenile soils, which are common in Sweden, they need to be inoculated with their symbiotic partner, the bacteria Bradyrhizobium japonicum. Task of the present study was to investigate the need for re-inoculation of soybeans in cropping sequences where soybeans are included. For this purpose we collected samples from soils in which soybeans had been grown previously and used these soils to grow soybeans in a greenhouse. We found that B. japonicum survived in the soils in which soybeans had been grown previously. Soil factors such as pH, nitrogen content and organic matter showed varying and inconsistent effects on the survival rate of B. japonicum, making it difficult to estimate their impact significance. However, application of nitrogen (as manure) and high amounts of phosphorus in soil appeared to promote B. japonicum survival. The amount of potassium in soil had varying effects, but high amounts appeared to impair B. japonicum survival. As regards to soil type, B. japonicum survived better in light soils than in clayey soils. We conclude that it could be recommended for growers not to re-incoulate their soybeans if the crop has been cultivated in recent years.
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