Combined Effects of Hybrid Pressurized Irrigation and High-Intensity Legume Intercropping on Productivity, Water Use Efficiency, and Soil Carbon Dynamics in Sugarcane-Based Cropping Systems

To evaluate the combined effects of hybrid pressurized irrigation (drip irrigation for sugarcane and micro-sprinkler irrigation for intercrops), legume-based intercropping, and residue incorporation on crop productivity, water use efficiency, soil organic carbon dynamics, and carbon sequestration in a sugarcane-ratoon I-ratoon II production system. A three-year field experiment (2017–2020) was conducted at RPCAU, Pusa, Bihar, India. Eight treatments involving different irrigation methods, intercropping systems, and residue management practices were evaluated in a randomized block design with three replications. All parameters were assessed across the plant crop, ratoon-I, and ratoon-II. Drip-irrigated sole sugarcane produced the highest cane yield (107.3, 102.1 and 98.4 t ha−1) in plant, ratoon I and ratoon II, compared with surface irrigation, respectively. The highest cane equivalent yield (154.0–159.1 t ha−1) and soil organic carbon stock (33.6 Mg ha−1) were recorded under hybrid pressurized irrigation + French bean–green gram intercropping + residue incorporation. Drip irrigation improved water use efficiency by 92% (1529 kg ha−1 cm−1). After three crop cycles, T8 recorded maximum total soil organic carbon (17.81 g kg−1), particulate organic matter (3.62 g kg−1), soil microbial biomass carbon (292.5 mg kg−1), carbon pool index (1.52), carbon lability index (1.54), carbon management index (234) and soil organic carbon stock (33.6 Mg ha−1), indicating improved soil carbon accumulation and sequestration. Integration of hybrid pressurized irrigation, legume intercropping, and residue incorporation improved productivity, water use efficiency, profitability, soil health, and carbon sequestration, and T8 treatment emerged as the most sustainable option for enhancing resource-use efficiency and long-term soil carbon storage in sugarcane-based cropping systems.