Green Manure Modulates Soil–Plant–Microbial Responses to Increasing Irrigation Salinity in a Semiarid Agroecosystem

ABSTRACT

Soil salinisation under saline irrigation is a major constraint to agricultural productivity in semiarid regions. This study evaluated how legume‐based green manure systems influence soil chemistry, microbial biomass and maize nutrition under increasing irrigation salinity. A two‐cycle field experiment combined four legume species with three irrigation salinity levels (1.5, 3.0 and 4.5 dS m ⁻¹ ). Soil fertility, exchangeable cations, microbial biomass and respiration, leaf nutrients and maize dry matter were assessed. Structural equation modelling (SEM) was used to evaluate soil–plant–microbe interactions. Increasing salinity elevated soil electrical conductivity and sodium accumulation while reducing organic carbon, available phosphorus and exchangeable potassium. Cumulative stress decreased microbial biomass and respiration, particularly in the second cycle. Leaf potassium decreased and sodium increased, causing ionic imbalances that reduced maize dry matter. However, green manures improved soil fertility and supported microbial biomass, promoting better plant nutritional balance. SEM revealed that salinity primarily affected maize indirectly via soil chemical changes, with green manure partially buffering these effects. Thus, organic management enhances system resilience against soil‐mediated salinity impacts, although it does not fully offset saline stress.