Sugarcane is the leading feedstock for bioethanol in Brazil and worldwide, but its continuous cultivation can degrade soil through nutrient depletion and compaction. Integrating green manures such as Crotalaria and pigeon pea into rotations offers a sustainable way to improve soil structure, water infiltration, and nutrient cycling. When combined with sweet sorghum as a complementary crop, these species can mitigate soil physical constraints and strengthen the resilience of sugar–energy systems under rainfed conditions. This three-year field experiment evaluated the effects of green manure and sweet sorghum rotations on sugarcane yield and sandy-soil physical attributes. The treatments were arranged in a 3 × 2 factorial design with randomized blocks, including two green manures (Crotalaria and pigeon pea) and a fallow control, each combined with or without sweet sorghum rotation. Biometric traits and yields were measured for all crops, and soil physical properties were assessed after the sugarcane cycle. Green manure significantly increased the stalk yield and dry matter of both sweet sorghum and sugarcane. In sugarcane, rotations with Crotalaria and pigeon pea enhanced stalk and dry matter yields by up to 18%, while the highest increase (31%) occurred under the sweet sorghum rotation. Furthermore, green manures improved sandy-soil water retention, increased infiltration rates, and reduced penetration resistance. These results demonstrate that legume–sorghum rotations are an effective and low-input strategy to enhance crop yield and sandy-soil physical properties, contributing to more sustainable bioenergy production under tropical rainfed conditions.
Nascimento et al. (Tue,) studied this question.