Cana-de-açúcar cultivada sob diferentes lâminas de irrigação, doses de nitrogênio em solo com e sem subsolagem

Abstract

Sugarcane is a crop of great importance in the world scenario for the production of sugar, ethanol and biomass; although being cultivated in several regions of the world, water and nitrogen are limiting factors for its production. The objective of this study was to evaluate the effect of different nitrogen doses and irrigation slides on sugarcane cultivated under soil conditions with and without subsoiling. A field experiment was carried out on cane soca in the 4th crop leaf using the variety RB92579 at the Experimental Sugarcane Station of Carpina - EECAC / UFRPE. Nitrogen doses (0, 40, 80, 120 and 160 kg ha-1) and irrigation slides (0, 50, 100 and 150% of crop evapotranspiration) were arranged in strips under and without subsoiling conditions in blocks, 5 × 4 × 2 with 3 replicates. Sugarcane productivity was then determined and the production functions, maximum production regions, marginal substitution rate, rational production region, and yield of sugar and alcohol in soils with and without subsoiling were determined. In order to verify the effects of the treatments on the photosynthesis of the plants, the chlorophyll fluorescence analysis was performed at 150 days of cultivation on leaves +1 adapted to the dark. From the collected data the JIP Test parameters were calculated. The maximum N levels and slides were 2033 mm and 131 kg ha-1 for the soil without subsoiling and 1729 mm and 137 kg ha-1 for the soil with subsoil with the respective yields of 125 and 127 Mg ha-1, with the region of rational production delimited by the regions of maximum productions. For the higher yield of sugar and alcohol the application of inputs must remain in the region of rational production until the minimum of 80 kg h-1 N and 1456 mm of water because smaller combinations of inputs decrease the yield of sugar and alcohol. The performance of photochemistry in sugarcane plants grown in subsoil soil is higher than in those grown in non-subsoil soil. Blade greater than or equal to 100% of ETC and doses of N greater than or equal to 80 kg ha-1 were more efficient photosynthetically in both subsoil and subsoil conditions.