Calla lily intercropping in rubber tree plantations changes the nutrient content, microbial abundance, and enzyme activity of both rhizosphere and non-rhizosphere soil and calla lily growth

Abstract

Rubber is a globally important crop species and is widely grown in Hainan, China; the development of efficient agricultural practices is essential when attempting to maximize productivity. The effects of interspecific competition for nutrients and calla lily (Alocasia macrorrhizos L.) intercropping on calla lily growth, development, and nutrient uptake were investigated in rubber tree (Hevea brasiliensis Müll. Arg.) plantations. The nutrient abundances, enzyme activity, and number of microbes present in rhizosphere and non-rhizosphere soil were determined. Barriers were inserted between the crops to separate their root systems and nullify belowground competition to facilitate the analysis of intercrop competition. We found that in the rubber tree/calla lily intercropping system, nutrient content and soil urease activities in rhizosphere and non-rhizosphere soil significantly decreased, and nitrogen (N) and potassium (K) taken up by calla lilies, and the growth and biomasses of calla lilies significantly decreased. In contrast, soil sucrase, acid phosphatase, and catalase activities and the quantity of fungi in rhizosphere and non-rhizosphere soil significantly increased, and phosphorus (P) uptake, root length, and the ratio of root to shoot dry weights in calla lilies also significantly increased. Intercropping significantly decreased the abundances of both bacteria and actinomycetes and decreased total microbial abundance in rhizosphere soil, but significantly increased their abundances in non-rhizosphere soil. The nutrient content (excluding organic matter content and pH) in rhizosphere soil was lower than in non-rhizosphere soil. These findings indicate that nutrient competition between rubber trees and calla lilies was significant in this intercropping system, with rubber trees holding a competitive advantage. Intercropping significantly inhibited calla lily growth by significantly decreasing soil nutrient content. The abundances of soil microbes and changes in root architectures correspond to the responses of calla lilies to nutrient competition, allowing the adjustment of the plants’ nutritional needs during growth and development.