Influence of inoculation and phosphorus regimes on symbiotic nitrogen fixation and phosphorus use efficiency of Algerian cowpea (Vigna unguiculata L. (Walp.)) landraces

ArticleTo 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 farm er’s dependence on fertilizers

Intercropping Promotes the Ability of Legume and Cereal to Facilitate Phosphorus and Nitrogen Acquisition through Root- Induced Processes

Intercropping of cereal and legume can improve the use of resources for crop growth compared to cropping system. An increase in soil phosphorus (P) and nitrogen (N) acquisition by root-induced biochemical changes of intercropped species has been reported as key processes of facilitation and complementarily between both intercropping legumes and cereals. Indeed, the functional facilitation prevails over interspecific competition under nutrients limiting for crop growth. Results showed that P availability significantly increased in the rhizosphere of both species, especially in intercropping under the P-deficient soil conditions. This increase was associated with high efficiency efficiency in use of rhizobial, plant growth and resource use efficiency as indicated by higher land equivalent ratio (LER) and N nutrition index. In addition, the rhizosphere P availability and nodule biomass were positively correlated (r2 = 0.71**, and r2 = 0.62**) in the intercropped common bean grown at P-deficient soil. The increased P availability presumably improved biomass and yield in intercropping, although it mainly enhanced intercropped maize grain yield. Exploiting belowground parameters in a legume-cereal intercropping is likely necessary to maximize rhizosphere-interspecific interactions as a strategy to improve the symbiotic rhizobial efficiency and microbial activities, as a result of root-induced pH and N availability changes under low P soils

Nodular diagnosis of contrasting recombinant inbred lines of Phaseolus vulgaris in multi-local field tests under Mediterranean climate

Common bean (Phaseolus vulgaris L.) has the capacity to fix atmospheric N-2 into the biosphere through its aptitude to establish a symbiosis with soil rhizobia. In order to search for environmental constraints that might limit this symbiosis a nodular diagnosis was performed in eighteen field sites chosen with farmers of the Setif agro-ecosystem. Common bean was used as a model grain-legume with six recombinant inbred lines (RILs) and one local genotype Djadida. At flowering stage, the biomass of plants and nodules was determined by excavating 20 cm in depth and around the root-system of ten plants per genotype and per site. The results indicate a large spatial variation in nodulation and growth between genotypes, and the distribution of soils in four soil clusters, based on physico-chemical properties. The inhibition of nodulation of all genotypes in soil of clusters A and B was associated with high residual soil mineral nitrogen (2.23 +/- 0.49 g kg(-1) soil). The low nodulation of all genotypes in the phosphorus (P) deficient soil of cluster C (6.73 +/- 3.63 mg kg(-1) soil) was partly compensated by increasing their efficiency in use of the rhizobial symbiosis (13%), estimated by the slope of the regression model of shoot biomass as a function of nodule biomass. Interestingly, significant correlations were found between nodulation of all genotypes and Olsen-P content in soils of clusters C (R-2 = 0.97, P < 0.001) and D (R-2 = 0.94, P < 0.05). It is concluded that the RILs selected for their efficient use of P for symbiotic nitrogen fixation show the highest nodulation and growth and that the nodular diagnosis can be used to assess the growth response of N-2-dependent grain-legume to soils with low availabilities of N and P

The intercropping cowpea-maize improves soil phosphorus availability and maize yields in an alkaline soil

Aim: This study assessed whether growing cowpea can increase phosphorus (P) availability in the rhizosphere and improve the yield of legume-cereal systems. In alkaline Mediterranean soils with P deficiency, it is assumed that legumes increase inorganic P availability.Methods: A field experiment was conducted at the Staoueli experimental station, in Algiers province, Algeria, to compare the growth, grain yield, P availability, and P uptake by plants with sole-cropped cowpea (Vigna unguiculata L. cv. Moh Ouali) and maize (Zea mays L. cv. ILT), intercropped cowpea-maize, and fallow. Results: P availability in the rhizosphere was increased in both sole cropping and intercropping systems compared with fallow. It was highest in intercropping. The increase in P availability was associated with (i) significant pH changes of the rhizosphere of cowpea in sole cropping and intercropping systems, with the rhizosphere acidification significantly higher in intercropping (−0.73 units) than in sole cropping (−0.42 units); (ii) significant increase in the rhizosphere pH of intercropped maize (+0.49 units) compared to fallow; (iii) increased soil respiration (C-CO2 from microbial and root activity) in intercropping compared with sole cropping and fallow; and (iv) higher efficiency in utilization of the rhizobial symbiosis in intercropping than in sole-cropped cowpea. Conclusion With cowpea-maize intercropping, cowpea increased the P uptake, by increasing the P availability by rhizosphere pH changes in an alkaline soil. Overall, this study showed that intercropping cowpea improved the plant biomass and grain yield of maize in this soil