Brown manuring in rice farming: unlocking new horizons for growth and productivity

Abstract

In India, agricultural practices are evolving to enhance resource management, with "brown manuring" (BM) emerging as a significant method for rice cultivation. Unlike traditional green manuring, which involves pre-planting cultivation and multiple tillage practices that can lead to soil moisture loss and increased irrigation needs, brown manuring offers a more efficient alternative. This technique involves the simultaneous cultivation of green manure crops such as dhaincha, Sesbania, and sunhemp with rice. These crops are later terminated using selective herbicides like 2,4-D, which causes a loss of chlorophyll and a brown appearance, hence the term "brown manuring. "Brown manuring effectively addresses the challenges of conventional green manuring by minimizing soil disturbance and reducing water usage. Research has demonstrated that this method can reduce weed density by approximately 50 percent and decrease total weed biomass by 37-80 percent without negatively impacting rice yield. Specifically, brown manuring with Sesbania suppresses broad-leaved weeds by 76-80 percent and grassy weeds by 20-33 percent, while also enhancing soil physicochemical conditions. The integration of brown manuring with herbicide application is particularly relevant in managing herbicide-resistant weed populations and mitigating shifts in weed dynamics. By employing green manure crops as intercrops and then terminating them with post-emergence herbicides, this method provides a dual benefit: enriching soil organic content and controlling weed growth through the shading effect of decomposing manure. Compared to traditional methods, brown manuring proves to be a more practical, resource-efficient, and environmentally sustainable approach to rice cultivation.