Influence of inoculation and phosphorus regimes on symbiotic nitrogen fixation and phosphorus use efficiency of Algerian cowpea (Vigna unguiculata L. (Walp.)) landraces
Integrative Breeding of Vegetable Production Laboratory, National High School of Agronomy, Avenue Hassen Badi, El Harrach, DZ16200 Algeria
To study the genotypic variation of cowpeas on plant growth and phosphorus (P) uptake which is a function of different P regimes in the soil rhizosphere, 6 landraces of cowpea commonly found in northern Algeria (NE4, NE10, NE11, NKT5, NKT7, NKB7) and 4 landraces from Sahara in southern Algeria (NAG4, NAG5, NAT2 and ND3) were studied during 2013–2014 in greenhouse. They were inoculated with Mesorhizobium sp. (S1), Bradyrhizobium sp. (S2) and co–inoculation (S1–S2) under three P treatments: no P supply (P0), soluble P (PP) and insoluble P (TCP). Only varieties commonly found in northern Algeria nodulated with soluble P (PP) and inoculation containing Mesorhizobium sp. (S1). As a result of the symbiosis, the use of S1 has significantly increased shoot dry weight by 22%, total P content by 20% and P use efficiency for symbiotic nitrogen fixation by 18% compared to no inoculation (T). The landraces from the northern of Algeria expressed a higher growth than those from Sahara in the south of Algeria, especially three of them (NE4, NE10 and NE11) who showed a high performance under all P regimes. We suggest that these three landraces may be useful for improving symbiotic nitrogen fixation in cowpeas when growth is limited by low–P soils and that they could contribute to sustainable farming systems through reduction of farmer’s dependence on fertilizers.