Agronomic performance of sugarcane cultivated under different amounts of sugarcane straw on the soil surface

Mechanized harvesting has become increasingly common in the sugarcane production system. The sugarcane straw removed by mechanical harvesting could be converted into ethanol or be used to generate electricity by burning the material. At the same time, it is important to determine the amount of biomass that could be removed from the soil surface without damage to the cane crop. The agronomic performance of sugarcane was evaluated by growing the variety RB92579 under different amounts of sugarcane straw on the soil surface, in the first and second years of cane crop growth. An experimental randomized block in a split-plot design was used with four replications. In the first year the plots received five amounts of straw (0.0, 4.5, 9.0, 13.5, and 18 Mg ha(-1)), and six assessments (60, 120, 180, 240, 300, and 360 days after planting) were made in the subplots. In the second year, the plots received the same amount of straw and four assessments (60, 120, 240, and 540 days after the regrowth) in the subplots. Biometric indexes, components of production, and crop yield were evaluated. The data were submitted to variance analysis and polynomial regression (p < 0.05). Increasing amounts of sugarcane straw deposited on the soil surface reduced the number and diameter of stalks at the beginning of crop establishment and the number of leaves for the first year. The maximum productivity of stalks was achieved by maintaining on the soil surface 9.6 Mg ha(-1) of straw in the first year and 4.7 Mg ha(-1) of straw in the second year of cane crop production.