Desempenho agronômico da cana-de-açúcar (Saccharum officinarum) em resposta a adubação nitrogenada e potássica

Abstract

Sugarcane cultivation has been consolidated as one of the main raw materials for bioenergy production, in addition to the importance already established for sugar production. With bioenergy production, several questions arise regarding the management and use of inputs, being the use of nitrogen (N) one of the main topics that have been discussed. Differences in response to N and potassium (K) as a function of crop cycles have required producers to be increasingly precise in choosing the doses to be used for fertilization, which, with the emergence of more productive varieties, has required more studies related to the theme. Therefore, this study aimed to evaluate the response of sugarcane crop to different doses of nitrogen and potassium. The experiment was carried out in the experimental area Garden Chã belonging to the Centro de Ciências Agrárias da Universidade Federal da Paraíba (UFPB). The experimental design was randomized blocks with 11 treatments and four replications. The treatments were arranged according to Plan Puebla III matrix, consisting of the combination of five doses of N in the form of urea (6.75; 40.5; 67.5; 94.5 and 128.25 kg ha-1) and five doses of K in the form of potassium chloride (9; 54; 90; 126 and 171 kg ha-1) plus additional treatment (without fertilization). The furrows were opened at 0.3 m depth, with 1.0 m distance between furrows. After opening the furrows, the seedlings were distributed in such a way as to obtain 15 viable buds per linear meter. These were covered with a 0.1 m layer of soil. Phosphorus (P) was applied in a single dose at the bottom of the furrow, along with the treatment corresponding to the N and K dose, before seedling disposal. Root biomass, total yield and crop nutritional status were evaluated at different times. The obtained data were submitted to the analysis of variance with unfolding of the quantitative effects in regression components, according to their significance by the F test. Nitrogen and potassium fertilization influenced the physiological performance of sugarcane, where the doses of 67.5 + K2O 90 kg ha-1; 6.75 + K2O 54 kg ha-1 and 40.5 + K2O 9 kg ha-1 of nitrogen and potassium, respectively, were the ones that best increased plant growth and root biomass. The maximum sugarcane yield (94,425.48 kg ha-1) was reached when the plants were fertilized with 63 kg ha-1 potassium and 128.25 kg ha-1 nitrogen. Regarding the years (cycles) of sugarcane evaluation, it was found that plants fertilized with nitrogen and potassium presented higher productivity than those not fertilized. In Brejo Paraibano it is economically viable to maintain sugarcane until the third cycle of production in unfertilized sugarcane and fourth cycle in fertilized sugarcane.