Mechanisms of AMF Regulating Rhizosphere Microenvironment and Physiological Metabolism in Areca/Vanilla Intercropping System under Nitrogen Reduction

This study systematically investigated the response mechanisms of the rhizosphere microenvironment and physiological metabolism in an areca/vanilla intercropping system under three nitrogen reduction levels (conventional, 30% reduction, and 60% reduction) combined with inoculation of two arbuscular mycorrhizal fungi (AMF). The results showed that under 30% nitrogen reduction, inoculation with AMF (C.e) significantly increased soil hydrolytic nitrogen by 26.29% (P < 0.05), while AMF (F.m) enhanced soil organic matter and available potassium by 10.93% and 2.38%, respectively. AMF exhibited species-specific regulation of soil enzyme activities. For instance, under conventional fertilization, AMF (C.e) increased phosphatase activity by 25.68%, while under 60% nitrogen reduction, AMF (F.m) boosted urease activity by 64.46%. Additionally, nitrogen reduction combined with AMF inoculation significantly promoted the accumulation of glomalin-related soil protein (GRSP), with AMF (F.m) increasing GRSP content by 5.16%. This study demonstrates that AMF optimizes rhizosphere nutrient cycling and soil structure, providing a theoretical basis for reducing fertilizer application and enhancing ecological intensification in tropical intercropping systems.