Genotypic variation for phosphorus uptake dinitrogen fixation in cowpea on low‐phosphorus soils of southern Cameroon uri icon

abstract

  • In cowpea, efficient N-2-fixing genotypes are being selected to promote sustainable cropping systems in southern Cameroon (SC). However, N-2 fixation and growth of these genotypes are largely hampered by low levels of soil plant-available P. To evaluate the genotypic variation in N2 fixation and P uptake among cowpea (Vigna unguiculata L.) genotypes, field experiments were conducted over two years on two acid soils low in available P. The experiments were laid out in a split-block design with four replications on typic (TK) and rhodic (RK) Kandiudult soils with seven cowpea genotypes. Phosphorus (P) fertilizers were applied on the main plots with 0 kg P, 30 kg P ha(-1) as triple superphosphate (TSP) and 90 kg P ha(-1) as Togo phosphate rock (PR). Nodule dry matter (DM), shoot DM, grain yield, and P uptake of cowpea significantly varied with site, P application, and genotype (p < 0.05). The N2 fixation of the cowpea genotypes ranged from 29 to 51 kg N ha(-1) on both TK and RK soils and was significantly increased with P application. Significant genotypic variations in N-2 fixation were observed with superior ability of the genotypes IT89KD-391 and IT90K-59 to fix N-2. The harvest index (HI) did not significantly differ between soils and P application levels (p > 0.05). Four genotypes were selected to investigate root mechanisms responsible for efficient P acquisition in pot experiments. The results suggest that a better root infection by arbuscular mycorrhizal fungi (AMF) in genotype IT90K-59 and root morphological and physiological characteristics in IT89KD-391 were the most important factors for increasing P uptake.

publication date

  • 2006
  • 2006