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The aim of this controlled environment experiment was to quantify the distribution of leaffed-15 N and canopy fed-13 C within nodulating, nonnodulating or N fertilized non-nodulating Cicer arietinum L. and in their surrounding rhizosphere soil, excluding soil+root respiration. Nodulating chickpea partitioned 32% of its total N and 27% of its total recoverable C below-ground, of which only 50% of N and 36% of C were in the clean root fraction. Non-nodulating chickpea allocated equal recoverable C but slightly less N (28%) below-ground but lost less C from plant induced below-ground respiration. The importance of this below-ground partitioning for crop systems C and N balances is highlighted by their large (45% and 33%, for N and C, respectively) contribution to the total plant derived residue (recyclable) fraction. Recovered 15 N and 13 C were greater (P<0.05) in the outer-rhizosphere (459µg 15 N and 3.2 mg 13 C core −1 ) than in the inner-rhizosphere soil (detached from roots during freeze-drying; 18µg 15 N and 67µg 13 C core −1 ) in relation with the relative size of these compartments. This highlights the significance of the outerrhizosphere soil when estimating C and N budgets and quantifying rhizodeposition, and the benefit of a double ( 15 N, 13 C) isotope approach to determine this flow against large background soil C and N pools.

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The effect of nitrogen application on biomass production and yield of legumes and maize under rainfed field conditions was studied to estimate the amount of nitrogen fixed by various leguminous crops under fertilized and non-fertilized conditions and to compare the yield, income and net return of legumes and non-legumes. Yield and biomass of summer legumes were not affected significantly with N application but in case of maize there was an increase of 69 and 74 percent in dry matter and grain yield, respectively. The nitrogen application significantly increased straw yield of summer legumes but had a negative effect on N-fixation at flowering and at pod fill stage.