Influence of phosphorus on nitrogen fixation in chickpea cultivars

Abstract

Phosphorus (P) is a major nutrient factor influencing nitrogen (N) accumulation and partitioning of photosynthates in plants, especially the symbiotic N₂‐fixation in legumes. This study was conducted to investigate how P application (0, 20, 40, and 60 kg P₂O₅/ha) affects symbiotic N₂‐fixation of three cultivars (C 235, Pusa 408, and Pusa 417) of chickpea (Cicer arietinum L.). Application of P in general significantly increased leaf area, shoot dry weight, and the rate of acetylene (C₂H₂) reduction. Phosphorus concentration of shoots and roots, soluble sugar content of nodules, and shoot N accumulation were also significantly increased, especially by P at the 40 kg P₂O₅/ha rate. The P concentration in nodules was, however, not affected by different levels of P. The Pusa 417 cultivar responded better than the others to the P treatments. Phosphorus‐deficient plants accumulated sugar in their leaves. The interaction effect was found significant on leaf area, shoot dry weight, nodule number, and shoot N accumulation. Pusa 417 gave greatest response to 40 kg P₂O₅/ha but Pusa 408 and C 235 interacted best with the 20 kg P₂O₅/ha rate only. The increased nodulation and symbiotic N₂‐fixation on P application seem to be the result of morphologically advanced shoots which are making more photosynthates for transport to nodules and not the direct effect of P on the nodules.