Estado nutricional da variedade RB92579 nos ciclos de cana-planta, primeira, segunda e terceira rebrotas

Abstract

The sugar cane crop is one of the most important cultivated in Brazilian territory, with one of the largest planting areas in Brazil, behind only corn and soybeans. It is possible to obtain products such as sugar, ethanol, bioenergy, waxes, tinctures as well as their use in animal feed. The growth and expansion of sugarcane production is a consequence of the implementation of technologies that aim to increase the productivity and profitability of the sugar cane crop. Among the main technologies adopted, we can highlight soil analysis, liming and plastering, green and organic fertilization, efficient use of chemical fertilizers, pest and weed control, irrigation and correct choice of sugarcane varieties. Genetic breeding programs have increasingly made available varieties that are well adapted to the edaphoclimatic and high productive potential conditions. For the available varieties, it is important to know the nutrient extraction, aiming at future fertilization recommendations, especially the fertilization of the refund and the mineralization of the cane straw harvested without burning. The variety RB92579 has been the most planted in the state of Alagoas, its harvested area increased 37% between the years 2000 to 2015 for the Northeast region of Brazil. It has been well accepted by sugarcane producers as well as in planted areas in the mills, thanks to its high tillering, good agricultural productivity, high Total Recoverable Sugar (ATR) content and high recovery under conditions of water stress. Given its importance for agricultural production and for the state economy, the present study had the objective of evaluating the nutritional status of the sugarcane variety RB92579 in each cycle: sugarcane, first, second and third regrowth; and analyze the nutritional status throughout the four cuts made. The study was conducted in Triunfo Usina experimental area, in the city of Anadia - AL. The experimental design was a randomized block design, with five replications. In the phase prior to the study, soil samples were collected for fertility evaluation in the 0-20cm and 20-40cm depth layers. The soil acidity correction was applied with the objective of increasing the saturation by bases to 60%. The soil was plowed and barred, then furrowed. The plots were constituted of seven grooves of 8.0 meters in length, spaced of 1,00 meters. In the cane-plant cycle the chemical fertilization, applied at the bottom of the planting groove, was the one usually used by the plant: 500 kg per hectare from 09-14-22. The regrowths were fertilized with 500 kg ha-1 of fertilizer 20-05-25, with manual fertilizer distribution. In the maximum growth stage of the cane, leaves +3 were collected to evaluate the nutritional status of the plants. With the results obtained, the data were submitted to analysis of variance and the means test. There was a difference in the nutritional status between the cycles of the variety RB92579 for nitrogen, phosphorus, magnesium, iron, sulfur and boron. Copper and manganese deficiency were observed during all evaluated cycles and that this deficiency has been recurrent in other studies carried out by this research group. It was verified, in the cane-plant cycle, the phosphorus deficiency that remained in the first regrowth cycle. For the second regrowth cycle, there was deficiency only for copper and manganese. The third regrowth presented insufficient levels for phosphorus, sulfur, nitrogen, copper and manganese. For the other nutrients, the presented contents were in the ideal range for the culture.