Soil fertility effects on nodulation,nitrogen fixation,and yields of guar, (Cyamopsis tetragonoloba (L.) Taub.), grown on a typic eutrustox

Guar (Cyamopsis tetragonoloba (L.) Taub.) is a legume of unusual industrial importance due to increased utilization of Guar gum, ‘Guran,’ in numerous modern manufacturing and food processes. Guar has high tolerance of drought and inhibitory soil characteristics and has been utilized for many centuries within the subhumid regions of the Indo‐Pakistan subcontinent. Nodulation, nitrogen fixation, and yields of high protein seed with desirable Guran content are improved by favorable soil fertility. Plant growth, seed yields, and nodulation are influenced by plant population density.

Top Growth quadratically increased with plant population densities of 10, 25, and 50 plants per meter² for P and P+K treatments. Highest seed yield and nodule development resulted for all soil fertility treatments with 25 plant per meter². Ontogenetic response from anthesis to full seed maturity resulted with increased nodulation significantly correlated (r = 0.67) with top growth. However, nitrogenase activity levels plant‘¹ declined significantly with plant maturity. Nodule cytosol enzyme activity levels at anthesis were: allantoinase (ALTN) 29.5 IU, aspartate transaminase (AST) 19.3 IU, glutamine synthase 12.5 IU, uricase (URC) 2.25 IU, and allantoicase (ALTC) 0.14 IU g^‐1 fresh nodule. Cytosol composition included ureidoglycolates (ureides) 425.8 μmol, amine‐amide content 29.5 μmol, nitrate 1.95 μmol, pyruvate 0.21 μimol, and oketoglutarate 0.09 μmol g‘¹ fresh nodule. Plant nutrient composition of nodule cytosol was K 394.9 jig, P 59.4 μg, Ca 48.9 μg, Mg 39. μg, and Na 19.0 μg g^‐1 fresh nodule. Precise histology with Giemsa and PAS procedures were essential for microscopy with cellular compartmentalization of purine enzymatic transformations governing nitrogenase activity and nodule development.