Transition in plant–plant facilitation in response to soil water and phosphorus availability in a legume-cereal intercropping system

Abstract

Background The tradeoff between negative and positive interactions of facilitated species and facilitators may depend on the degree of resource availability in agroecosystems. However, the rhizospheric mechanisms driving trade-offs that occur along phosphorus (P) and water availability gradients have not yet been systematically clarified. We established three types of root isolation conditions (no barrier, nylon barrier and solid barrier) at different P and water addition levels to address the above issue in a maize-grass pea intercropping system. Results The total yield and biomass net effect (NE) and the relative interaction index (RII) were significantly higher than 0 under all environmental conditions, demonstrating that plant-plant interactions generated positive effects in the intercropping system. The maize yield and biomass RII were 0.029–0.095 and 0.018–0.066, respectively, which indicated that maize growth was constantly facilitated. However, the RII for grass pea yield and biomass exhibited a different trend in comparison with maize. It was higher than 0 (as the facilitated species) under low soil P and moisture conditions and transitioned to values lower than 0 (facilitator species) under high P and moisture conditions, which showed that the type and intensity of plant-plant interactions steadily shifted with the applied stressors. Direct interactions decreased the maize rhizospheric soil pH by 1.5% and 1.9% under Low-P conditions. Notably, the rhizospheric soil acid and alkaline phosphatase secretions of maize and grass pea increased by 17.4–27.4% and 15.3–27.7%, respectively, in P-deficient soils. These results show that plant-plant interactions can effectively relieve P stress by mineralizing organophosphorus in P-deficient soils. Furthermore, the above tendency became more pronounced under drought-stressed conditions. The nylon barrier partially restricted the exchange and utilization of available nutrients and decreased the total yield and biomass by 1.8–7.8% and 1.1–7.8%, respectively. The presence of a solid barrier completely restricted interspecific rhizospheric interactions and decreased the total yield and biomass by 2.1–13.8% and 1.6–15.7%, respectively. Phytate and KH2PO4 addition intensified asymmetric interspecific competition, and grass pea was consistently subjected to competitive pressures. Conclusion Briefly, the tradeoff between facilitation and competition was driven by rhizospheric interactions, and the transition in the intensity and type of interaction was highly dependent on resource availability in a biologically diverse system.

Maize/Soybean Intercropping with Straw Return Increases Crop Yield by Influencing the Biological Characteristics of Soil

“…Under conditions of long-term maize monoculture and continuous cropping, the soil microbial community structure is relatively uniform, but as more nutrients are released into the soil after the straw decays, that original state of dynamic equilibrium is disrupted, and this may greatly promote the growth of certain microbes. However, in the cultivation of corn and soybean intercropping systems, using different crops can have a greater impact on the microbial number, biomass, and population change in rhizosphere soil via interspecific interactions [ 43 ]. That view and our findings are consistent with previous work [ 44 ], showing that intercropping improves soil health and enhances the metabolic activity of microorganisms.…”

Maize intercropping enriches plant growth-promoting rhizobacteria and promotes both the growth and volatile oil concentration of Atractylodes lancea

“…This inconspicuous effect of intercropping may be due to the fact that our study provided adequate nutrition for A. lancea , and this must be considered against the fact that crop diversity largely exerts its effects by alleviating a stressful environment for plants to increase their growth; for example, in combating nutrient stress ( Liancourt and Dolezal, 2021 ). In one study, the plant-plant stimulatory effect was observably decreased with the reduction of stress in the intercropping of maize and grass bean under phosphorus and water deficiency conditions ( Zhu et al., 2022 ). Similarly, under either water sufficiency or drought stress conditions, intercropping increased grain yield by 14% and 93%, respectively, over monocropping ( Willey, 1990 ).…”

“…In many plant-plant interaction studies, the strength of the rhizosphere interaction determines plant growth outcomes ( Zhang et al., 2017 ; Xiao et al., 2020 ; Li et al, 2021 ), but in our study, some rhizosphere interactions of maize evidently failed to promote the growth of A. lancea . Maize is more competitive than A. lancea due to its dominant position in the nylon barrier intercropping system ( Li et al., 2011 ; Worku, 2014 ; Zhu et al., 2022 ), and is hence better able to absorb nutrients and soil moisture through the nylon barrier. Therefore, the rhizome weight of A. lancea in the AI treatment group was higher than that in the CK treatment group, but the result was not significant in this experiment.…”

The Effects of Incorporating Caraway into a Multi-Cropping Farming System on the Crops and the Overall Agroecosystem

“…Based on this, plants growing in a multi-cropping system form a more abundant plant root biomass, allowing for greater nutrient uptake from the soil [45]. Studies by Oelmann et al [46] and Zhu et al [47] show that biologically diverse plant communities make better use of phosphorus resources than less diverse ones. Well-developed roots cover a larger soil volume, leading to higher plant uptake of phosphorus, potassium, and other elements [28], such as nitrogen [48].…”