A cana-de-açúcar em sistema de plantio direto comparado ao sistema convencional com e sem adubação

The objective of this study was to evaluate the agronomic characteristics of sugarcane as a function of the no-tillage system (NTS) compared to the conventional one (CS) with, and without, manuring. The experimental design was completely randomized, using four repetitions, in a factorial scheme 4 x 2. The treatments were: sugarcane NTS on sunnhemp (Crotalaria juncea); sugarcane NTS on jack bean (Canavalia ensiformis); sugarcane NTS on black mucuna (Mucuna aterrima) and sugarcane CS with incorporation of spontaneous vegetation (control), being duplicated, since each one was with, and without, manuring. In nutritional terms, the sugarcane CS on leguminosae was 43% superior in content of K, and the prominence was jack bean and mucuna that on average provided 26% more foliar N in relation to sugarcane CS. The nutritional diagnosis also indicated N and K as the main limitants of the productivity of sugarcane CS, while Ca, Fe, Zn and Cu were independent limitants of the management system. K was the main nutrient limitant of the productivity of unfertilized sugarcane. Sugarcane NTS on leguminosae provides larger foliar contents of N and K, besides increasing in 27, 32 and 37%, respectively, the number, the diameter and the productivity of stems in relation to the sugarcane of CS. The sugarcane in NTS on leguminosae, besides being more productive, guarantees larger preservation of the environment due to the harvesting of the cane without prior burning.