Normas DRIS e diagnóstico nutricional de cana-soca na região sul de Goiás

Abstract

DRIS norms were developed for sugarcane and have been successfully used in some productivity areas. In order to improve the diagnoses obtained with the DRIS method, specific norms can be developed for some specific conditions. This work was carried out aiming to develop, compare and assess general and specific DRIS norms for first and second ratoon sugarcane crop in southern region of Goiás, Brazil. With this purpose, leaf samples of 156 commercial sugarcane (Saccharum spp.) crops were collected in the year 2012/2013. For the development of the norms, the samples were divided according to the yield of the plots. The plots with yield above average productivity plus 2/3 of standard deviation were considered of high yield. DRIS norms, consisting of the mean and coefficient of variation of the dual relationships between all the nutrients in the reference population, were calculated using the method of F-value. The DRIS indices were calculated. From these values, the Nutritional Balance Index (NBI) and the average nutrient balance Index (BNIa) were determined. The percentage of concordant dual relationships was calculated. The values of the concordant dual relationships were compared by "t" test (P < 0.05) and a model identity test was performed to compare the norms. Beaufils ranges were generated from the DRIS norms obtained, with which we calculated the frequency of plots in each class of nutrient content. Reference values for first and second ratoon sugarcane crop were different from each other and from the general norm obtained for the two development stage. The norms obtained in plots first ratoon sugarcane discriminated better the nutritional balance of ratoon sugarcane plots. Based on the Beaufils ranges obtained, the most limiting macronutrient, for deficiency were K and P. In turn, N and S were those more frequently in excess. Zn and Cu were the micronutrients most often lacking, while B and Mn were those in excess.