| Resumo: |
Nitrogen fixing capability of legumes can be enhanced by the supply of adequate amounts of nutrients, especially phosphorus (P) and sulphur (S). However, combined application of P and S may have synefgistic oí antognistic effects on crop yield, depending upon initial fertility status of soil, level of nutrients applied and test crop used. Field experiments were conducted at two different locations (Barani Agriculture Research Institute, Chakwal, and farmer's field, Talagang) in northern fainfed Punjab, Pakistan, to assess nodulation, nitrogen fixation and nutrient uptake by chickpea (Cicer arietinum L.) in response to application of P (0, 40 and 80 kg ha-1) and of S (0, 15 and 30 kg ha-1) in different combinations. Application of P and S significantly increased seed yield (27 to 41 % and 7 to 11 %) over control. Sulphur application increased N derived from ah- (% Ndfa) by 5 to 7 % over control; however, P application had no significant effect on Ndfa. Both P and S application increased N fixation (16 to 40 % and 15 to 22 %) over control. Nutrient uptake (N, P and S) increased significantly with the application of both P and S. There was a wreak correlation between P uptake and % Ndfa (R=0.28*) but a positive correlation between S uptake and % Ndfa (R=0.76**). Phosphorus (R=0.56") and sulphur (R=0.97**) uptake correlated positively with N fixation.
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