Subsolagem e irrigação em cana soca sob doses crescentes de nitrogênio

Abstract

Irrigation can provide great influence on the productivity of sugarcane, but part of the sugarcane fields under irrigation are still getting inadequate management of varieties and soil. Then, must be identified management that optimize the sugarcane yield and increase the crop longevity. Among these practices, the suitable fertilization after each harvest and the soil management combined with irrigation management, can contribute to increase productivity and longevity of sugarcane crop. Then, this study aimed to evaluate the effects of subsoiling on soil physical attributes with sugarcane growing after two harvests and on the retention water and productivity under nitrogen doses. The treatments were arranged in three blocks randomized with arrangement in split plots, composed of five levels of nitrogen (0, 40, 80, 120 and 160 t.ha-1) with and without subsoiling, being evaluated under rainfed and irrigated conditions resulting in two experiments. Soil physical properties were evaluated on 0-20; 20-40 and 40-60 cm, which are hydraulic conductivity, penetration resistance, bulk density, water retention curve and pore distribution by size. Additionally, some technological quality parameters of sugarcane were determined, as the productivity of stalks (TCH), tons of total reducing sugar per hectare and tons of Pol per hectare. The results were analyzed by F test (ANOVA) and the significant results have evaluated through a comparison of means using the Tukey test, at a level of 5% probability. Regression analysis was used for evaluate nitrogen levels effect. The results showed that subsoiling didn’t increase significantly the water soil retention since total porosity increased only in some layers. The density of the soil subsoiled reduced while, soil hydraulic conductivity increased by 50%, and as a result there was significant reduction in soil penetration resistance values. Among the technological variables, only productivity showed significant gains. The N rates favored a linear increase in productivity. Subsoiling tend to be a promising practice to contribute in maintaining the sugarcane yield after 2nd harvest.