Nutrients optimum range (NOR) based on DRIS method to assess the nutritional status of the first ratoon sugarcane

The development of nutrients optimum range (NOR) is quite important for the ratoon sugarcane (Saccharum spp.) to help decision making of fertilizers management. The purpose of this study was to establish NOR from statistical models of relationship between leaf nutrient content (LNC) and DRIS indices. In this study, the nutritional status of the first ratoon sugarcane crop was assessed based on NOR. The study was performed using data from the first ratoon sugarcane obtained from commercial fields, in the southern region of Goi s State, in Brazil. Yield data from plots (average acreage 20 ha) and LNC of macro- and micronutrients in 2012/2013 cropping season were stored in a database. The procedure to define the reference population (high-yielding subpopulation) consisted of plots with above-average yield + 2/3 standard deviation (over 200.94 tonnes ha-1). The average and coefficient of variation for each dual ratio between nutrient concentration (N/P, N/K, N/Ca, etc.) were measured in the high-yielding subpopulation, which was considered the DRIS norms. Based on DRIS norms at the first ratoon sugarcane, it was possible to develop NOR and assess the nutritional status of sugarcane crop. The evaluation of the nutritional status using the NOR indicated that K (87.36%), P (81.82%), Zn (67.27%) and Cu (76.36%) were the nutrients that showed the most deficiency among the plots assessed. On the other hand, N (69.09%), Ca (60%) and S (70.91%) were the most excess nutrients.