MANAGEMENT OF NITROGEN FERTILIZATION IN SUGARCANE: THE SEARCH TO FIND OUT ALTERNATIVES TO INCREASE THIS EFFICIENCY

Abstract

The use of sensors that allow the application of nitrogen fertilizer rate on variable has been widely used by researchers in agricultural crops, but without success in the cultivation of sugarcane, probably due to the difficulty of diagnosis of the nutritional status of culture in nitrogen (N). Furthermore, the application of nitrogen fertilizer without standardization stage of plant growth results in decreased efficiency of fertilizer nitrogen along with increased environmental impact. This research is based on the hypotheses that methods of diagnosing nutritional status of culture through active optical sensors are effective for predicting the need for N-fertilizer to be applied in the field, since the supply of nitrogen at different times affects the nutritional balance of culture in N. The objective is to assess the nutritional status of the culture of sugarcane fertilized with different nitrogen rates applied at different times after harvest, through diagnostic sensors in order to generate parameters for the sustainable application of N-fertilizer in sugarcane. So it, three experiments will be installed with the same experimental design, in commercial sugarcane same age (first ratoon), all planted with the variety IACSP95-5000, but harvested at different times within the sugarcane crop Center South of Brazil. The experiments will be evaluated for two consecutive years and will begin in area with early harvest (April), with the second half of the harvest season (July) and the third harvest in order to harvest (October). The experimental design is a randomized block in factorial 5x5 with four replications, and five levels of nitrogen (0, 50, 100, 150 and 200 kg N ha-1) applied in five seasons after harvesting the sugarcane plant (after cutting of stalks, 30, 60, 90 and 120 days after the cut - DAC). During the development of the crop (30, 60, 90, 120 and DAC 180) is evaluated nutritional status of culture in N through foliar analysis performed by chemical analysis (determination of N +1 of the sheet by the classical method Kjedahl ), chlorophyll a (read on leaf blades of leaves +1) and reading the crop canopy with active optical sensor. In every age assessment, biometric parameters of culture will be assessed for the standardization of the growth stage of the crop within each fertilization. All data will be correlated with nutritional diagnosis of sugarcane yield and sugar measured in the crop harvest. In the second year of the project beyond the evaluations described above, in the treatments with a dose of 100 kg N ha-1 (mean dose commonly used in culture) will evaluate the efficiency of N fertilizer applied at different times after cutting the first ratoon. For this technique 15N isotope tracer is used to measure the utilization of N from the culture of nitrogen fertilization. The results hoped for this project will help the management of N-fertilizer in the sugar plantations in Brazil, through diagnostic techniques associated with the stage of plant development ideal for monitoring "on-the-go" demand for N by sugarcane.