11. Evaluation of diverse effects of phosphate application on legumes of arid areas.
Trop. Agric. (Trinidad), 64, 2, 1987, 91-96
Low organic matter and low N in most soils of arid and semi-arid parts of Rajasthan present the opportunity for the adoption of a low-input approach towards improvement of fertility through the cultivation of legumes. It is also felt that soil N, thus augmented, might contribute much towards the yield improvements of subsequent cereal crops, particularly of pearl millet, grown extensively in these parts. In this regard, the importance of phosphate fertilization to legumes for the improvement of their performance and N2 fixation has been documented in a number of reports. Although mungbean, moth bean and clusterbean are widely cultivated in these parts, there seems to be little knowledge regarding the effects of phosphate fertilization on these legumes and succeeding cereal crops. Such an assessment, moreover, is particularly needed because of the uncertainty of monsoonal rains and the drought-prone nature of the region; the effects of P on the growth, yield and water-use of legumes in different rainfall situations assume importance. Again, the implication of P application on soil N enrichment and the consequent yield improvement of the succeeding cereal crop warrant special consideration in view of the reports of beneficial effects of P on soil N status, even in situations where the performance of the legumes was not influenced. This paper relates some findings in these areas.
Mungbean (Vigna radiata), moth bean (Phaseolus acontifolius) and clusterbean (Cyamopsis tetragonoloba), grown over three successive years under low and variable rainfall on loamy sand soils of arid western Rajasthan, did not reveal any marked effect of phosphate application (0, 20, 40, 60 and 80 kg P2O5ha-1) on the consumptive use of moisture. The effects on dry matter production and seed yield were marginal, but not significant. Uniform distribution of precipitation during the growing period, rather than its quantum, had the more favourable influence on plants. P application induced a small increase in the available P status of the soil and also in N and P uptake. But the weight of nodules per plant and root CEC progressively increased with increasing level of P up to 40-60 kg P2O5ha-1. Phosphate application also led to an increase in soil N, particularly of the hydrolyzable organic-N fraction. Effects on mineralized N were marginal. The amount of N2 fixed was greater in mungbean and moth bean than in clusterbean but the mineralized and hydrolyzable organic-N fractions increased more under clusterbean. While the phosphate levels did not have any effect on the succeeding pearl millet (Pennisetum typhoides) crop, the legumes significantly promoted its yield equivalent to > 80 kg N ha-1, despite the prevalence of acute drought conditions. The beneficial effect of clusterbean was found to be greatest, followed by moth bean and mungbean. It seems that the beneficial effect of legume cultivation arose not only from the total N2 fixed but also from the level of mineralized and hydrolyzable organic N contributed by plant residues left in the soil.
1248 92 - 12/74
Asia, India, dryland agriculture, field trial, clay loam soil, cropping systems, fertilizer, pigeonpea, sorghum, sole cropping, intercropping
PANDEY, R.C. et al.
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