Abstract
In Africa, intercropping and intra-hole cropping systems are common practices used by smallholder farmers to optimize land use and tap the benefits of plant-to-plant interactions. The aim of this study was to evaluate mineral nutrient concentrations, P-enzyme activity and changes in microbial communities in the rhizospheres of sole cropped and intra-hole planted cowpea (cvs. TVu 546 and PAN 311), maize (cv. ZM 521), and sorghum (cv. M48). Cowpea cv. TVu546 intra-hole planted with sorghum (i.e., TVu546+M48) produced the highest rhizosphere acid phosphatase (APase) activity (230.0 μg p-nitrophenol.g−1 soil.h−1). From 16S rRNA Miseq Illumina sequencing, the rhizosphere bacterial community structure was altered by intra-hole cropping, and was dominated by Actinobacteria, Acidobacteria, Bacteroidetes, Firmicutes, Planctomycetes, Proteobacteria, and Verrucomicrobia, which together accounted for about >95% of the total sequences. The Sphingobacteria phylum was the dominant microbial group in the rhizosphere soil of all the cropping systems. The Proteobacteria phylum was the second most abundant in this study, which included the beneficial bacteria in all the rhizosphere soils studied. In contrast, typical pathogens like Ralsotonia and Agrobacterium were completely absent, indicating that the intra-hole cropping system can provide protection against soil-borne diseases possibly through elimination by antibiotics and/or phytoalexins present in plant and microbial exudates in the rhizosphere. Mucilaginibacter and Flavobacterium were however selectively present with intra-hole cropping.
Highlights
Intercropping, defined as the planting of two or more crops on the same piece of land within the same cropping season, is an ancient cultural practice common among smallholder farmers, especially in Africa
Based on operational taxonomic units or OTUs (97% 16S rRNA identity), the results showed that the microbial communities were separated by rhizosphere soil of the test crop species and the cropping systems, indicating that there was a difference in the community composition (Figure 7)
acid phosphatase (APase) and AlkPase activities in the rhizosphere of monocultures of the two cowpea genotypes were generally higher than those of the cereals, be it sorghum or maize (Figure 3). This is consistent with the findings by Li et al (2004) which showed that chickpea secreted greater amount of APase than maize
Summary
Intercropping, defined as the planting of two or more crops on the same piece of land within the same cropping season, is an ancient cultural practice common among smallholder farmers, especially in Africa. The intercropping system can vary from intra-row intercropping, inter-row intercropping to intra-hole cropping, which involves two or more different plant species These intercropping systems are a common practice used by smallholder farmers in Africa to optimize. Rhizosphere Ecology of Sole and Intra-Cropping Systems land use as well as tap the benefits of plant-to-plant interaction. This practice is regarded as low-input and self-sustaining, in that, it enhances the amount of biomass and yield that is harvested per unit land area (Matusso and Mucheru-Muna, 2014). Where a legume is intercropped with non-legume, direct transfer of fixed-N from the legume to the non-legume can occur, leading to enhanced N nutrition of the companion crop (Xiao et al, 2004)
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