Genotypic Effect of Groundnut on Nodulation, N Fixation and N Balance in the Two Savannahs of Nigeria

Identification of high N-fixing groundnut genotypes and integrating them into the prevailing cereal-based cropping systems can reduce the need for nitrogen (N) fertilizers, thus minimizing their high cost and associated environmental consequences. This study was conducted to estimate the amount of symbiotically fixed N by groundnut genotypes and its contribution to soil N and yield of groundnut. Trials were carried out during the 2015 rainy season at Bayero University Kano (BUK) Agricultural Research Farm and the research farm of the Institute for Agricultural Research (IAR), Samaru-Zaria. The treatments comprised of 15 groundnut genotypes (ICG 4729, ICGV-IS 07823, ICGV-IS 07893, ICGV-IS 07908, ICGV- SM 07539, ICGV- SM 07599, ICGV-IS 09926, ICGV-IS 09932, ICGV-IS 09992, ICGV-IS 09994, SAMNUT-21, SAMNUT-22, SAMNUT-25, KAMPALA and KWANKWASO) arranged in a randomized complete block design in three replicates. Data on nodulation, nitrogen fixation and N balance were collected. The results of the study showed that ICGV-IS 09932 significantly fixed the highest amount of N at IAR location while the lowest was obtained in KWANKWASO. On the other hand, SAMNUT-22 fixed the highest N among the genotypes while ICGV- SM 07539 fixed the lowest N in BUK location. Similarly, SAMNUT-22 which fixed moderate to high amount of N but low to moderate NHI was the best genotype that imparted positively to soil N balance among the genotypes when only the grains were removed across the locations. On the other hand, SAMNUT-21 which fixed low to high amount of N to the soil but accumulated low N in its grains was the best genotype that left fairly close to zero nitrogen balance, even though imparted negatively on soil N balance when both grains and haulms were removed.