Relation between soybean nodulation byBradyrhizobium japonicum and intensity of infestation with the spider miteTetranychus cucurbitacearum (Saved) under different sowing dates and increasing amounts of nitrogenous fertilizer

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Abstract
Inoculation of soybeans withBradyrhizobium japonicum and also the time of sowing of soybeans were studied under N-fertilization with urea at 0, 96 and 192 kg N/ha. Intensity of infestation with the spider miteTetranychus cucurbitacearum (Saved) was followed over six weeks. Inoculation greatly enhanced nodule numbers and weight, dry weight and N content of 65-day-old plant, seed yield, seed N content, 100-seed weight and efficiency of use of N from urea. Counts of the spider mite were increased by inoculation and N fertilization but decreased sharply under late plantation. Fertilizer N proportionally decreased nodulation, N2-fixation and productivity of chemical fertilizer. A late sowing date gave the least seed production but the maximum percentage increase in seed yield if inoculated. This indicated a lower efficiency of chemical fertilizer N utilization and the necessity for inoculation.