Effects of Nitrogen and Phosphorus Application on Growth and Root Nodules of Mungbean under Sandy Soil Conditions

Abstract

Legume production under infertile sandy soil may be limited by low nitrogen (N) and phosphorus (P) availability in the soil. A study was conducted to assess the effects of N and P on growth, yield, and root nodules of mung bean under sandy soil conditions. Two pot experiments were conducted under a greenhouse environment and were laid out in a completely randomized design (CRD) with five replications. Experiment 1 consisted of two types of soils (sandy and loamy sand) and two P application rates at 0 and 13 mg P kg-1. Experiment 2 consisted of 10 fertilizer treatments that included two N treatments of 0 and 53 mg N kg-1 in combination with four P treatments of 0, 17, 34, 68 mg P kg-1, P only at 17 mg P kg-1, and a cattle manure that was applied at a rate of 5 t ha-1 which was equivalent to 52:07:56 (N:P:K mg kg-1). The results showed that crop growth and root nodules improved with P application in the loamy sand soil (containing medium P), but not in the sandy soil (containing low P). Nitrogen application also improved the crop growth and grain yield significantly in loamy sand soil. However, N application suppressed root nodule formation, an effect that was significant for the N2 fixation of the crop. Increase in the P rate did not alleviate the inhibitory effect of N on nodule formation. Since N and P fertilizer had opposite effects on root nodules, interactions between N and P need to be further investigated when considering the economic benefits of using these fertilizers.