Estimation of the nitrogen fixation by sugarcane cultivar NiF-8 using 15N dilution and natural 15N abundance techniques

The high population of endophytic diazotrophs in the stalk of the Japanese sugarcane cultivar NiF-8 described in our previous report suggests the possible significant contribution of biological nitrogen fixation (BNF) to the crop nitrogen nutrition. To estimate the amount of BNF in this cultivar, the proportion of biologically fixed nitrogen (%Ndfa) to the plant total nitrogen uptake was determined by N-15 dilution and natural N-15 abundance (delta(15)N) techniques. Using the delta(15)N method, the estimated %Ndfa by the sugarcane cv. NiF-8 under field lysimeter conditions ranged from 32 to 38% at 6 months after planting (MAP) and from 27 to 34% at 7 MAP. With the N-15 dilution method, the estimated %Ndfa by the sugarcane plants was 26.0% for the roots, 14.1% for the stem, and 20.5% for the leaves. These results indicate that the sugarcane cv. NiF-8 obtained part of its nitrogen requirements from BNF.