Rhizosphere Dynamics in Maize-Based Intercropping Systems
Cereal-legume intercropping is a key strategy in sustainable agriculture, aiming to enhance nutrient cycling, reduce fertilizer inputs, and improve agroecosystem resilience. However, the combined effects of maize genotype, intercrop identity, and soil context on rhizosphere processes remain insufficiently understood. This dissertation investigates how maize genotypic variation, intercropping configuration, and soil properties shape rhizosphere biochemical activity, microbial communities, and nutrient acquisition using greenhouse rhizotron experiments and multi-site field trials. In controlled rhizotron experiments, six contrasting maize genotypes intercropped with faba bean were analyzed using in situ zymography. Genotypes with deep axial roots and dense lateral branching generated pronounced hotspots of acid phosphatase and leucine aminopeptidase activity in shared root zones, indicating enhanced nutrient mobilization under legume intercropping. Field experiments at two agroecologically distinct Swiss sites compared maize intercropped with field pea or ryegrass. Field pea increased orthophosphate availability and phosphorus-solubilizing bacteria, whereas ryegrass promoted organic phosphorus stabilization and higher fungal abundance, including arbuscular mycorrhizal fungi. These effects were strongly modulated by soil properties. A third study using ¹⁵N isotope tracing showed that intercropping enhanced nitrogen uptake and mycorrhizal colonization. Genotypes differed in nitrogen acquisition strategies, demonstrating that functional mycorrhizal efficiency, rather than colonization level alone, governs nutrient use efficiency. Overall, the results demonstrate that maize root traits interact with intercrop species and soil context to regulate rhizosphere functioning and support genotype-informed intercropping strategies for sustainable, low-input agriculture.
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