Evaluating different green manuring plant species and stool destruction methods for enhancing sugarcane yield at Wonji-Shoa Sugar Estate, Ethiopia

The long-term intensive production system employed in the Sugar Estates in Ethiopia, characterized by monoculture, preharvest burning, and excessive tillage, has led to soil degradation with a concomitant decline in sugarcane yield. Therefore, a study was conducted at Wonji-Shoa Sugar Estate (WSSE) with the objective of evaluating the effectiveness of different green manuring plant species and cane stool destruction methods (SDMs) in improving cane yield. To that end, seven green manure plant species (sunn-hemp, lablab, cowpea, soybean, mungbean, dhaincha, and sugarcane trash) were evaluated under three SDMs (cultivating-out, spraying-out with herbicide, and maintaining the stool as it is) using a split-plot design. The experimental fields were established on two major soil types, with green manure crops incorporated into the soil before planting the sugarcane. The dry matter production and nitrogen contribution of the green manure plants, as well as the height, population, diameter, and yields of sugarcane, were determined and subsequently subjected to statistical and economic analysis. The results showed that cowpea, followed by lablab, dhaincha, and sunn hemp, were the most effective green manures in terms of improving cane performance, with up to 17–20 % yield advantage and 21–40 % net economic benefits over the control treatment. Additionally, the spraying-out MSD was as effective as the cultivating-out MSD, but both outperformed maintaining the stool. In conclusion, utilizing these green manuring crops in combination with the spraying-out SDM presents notable advantages for improved cane yield and enhanced economic benefits in a sustainable manner. Adoption of these practices, therefore, holds significant potential for reversing the constantly declining sugarcane yields at WSSE.