Diagnose nutricional e potencial de resposta a adubação em cana-de-açúcar (Saccharum spp.) na região de Tabuleiros Costeiros em Alagoas.

Leila Cruz da Silva

An experiment was carried out in the region of Coruripe, Alagoas, aiming to establish DRIS norms for the diagnosis nutritional status of sugarcane, calculate the nutrient indexes by the DRIS method, utilizing four criteria in order to obtain the norms: C1 nutrient relations with the highest variance ratio, C2 nutrient relations with the highest variation ratio and the lowest coefficient of skewness with a partial Box and Cox transformation, C3 every nutrient relation with a natural logarithm transformation and C4 nutrient relations with the highest variance ratio and lowest coefficient of skewness with a Box and Cox transformation for all the nutrient relations.. It was also evaluated the nutritional diagnosis when the DRIS norms were established by these criteria and a comparison of the nutritional diagnosis of five different methods of indexes of calculating of the Diagnosis and Recommendation Integrated System (DRIS) and Compositional Nutrient Diagnosis(CND), and, finally compare the optimum nutritional contents specifically for the crop studied, estimated by the Mathematical Chance, Diagnosis and Recommendation Integrated System(DRIS and M-DRIS) and Compositional Nutritional Diagnosis(CND), from data coming from the nutritional monitoring of 183 sugarcane commercial lots in the period of 2008-2009. The agriculture yield (TCH) of these lots were determined The concentration of N, P, K, Ca, Mg, S, Fe, Cu, Mn, Zn and B were determined, totalizing 110 nutritional relationships. The databank was made up of 183 samples, with 31 of those coming from areas with a high yield (reference population with yield above 80 t ha-1) and 152 samples coming from areas with a low yield (less than 80 t ha-1). The groups with the higher yield were utilized in order to generate the DRIS norms. The DRIS norms that were based on the largest variance ratio, associated with the lowest coefficient of skewness, resulted in a better selection of the relation between nutrient concentrations. The Box-Cox transformation of the relations that had a high coefficient of variation and/or skewness resulted in ratio values with a normal distribution. Thus, of all those 110 relations, 55 were chosen as specifics norms for the sugarcane culture, cultivated in the region of Coruripe-AL. The selection criteria of nutritional relations with a larger variance ratio for the establishment of DRIS norms werent satisfactory to evaluate the sugarcane nutritional status in the region of Coruripe, Alagoas. The DRIS norms based on the highest variance ratio associated with the lowest coefficient of skewness (C2 e C3) made it possible to have a better selection of the relation between the nutrient concentrations. However, the norms that used the C2, C3 and C4 criteria reduced the coefficient of skewness and established the normality of data, thus providing similar nutritional diagnoses among themselves. Regarding the DRIS methods, The nutritional diagnosis, depending on the chosen method used to make the nutritional evaluation of the crop, can lead to different interpretations,, compromising the recommendation of fertilizers. DRIS Beaufils, DRIS Jones, M-DRIS Beaufils and M-DRIS Jones methods tend to be consistent regarding the sugar cane nutritional diagnosis in the region of Coruripe, Alagoas. The CND method was not found in concordance with the N and Mn nutrients, compared to all the other methods verified in this study. M-DRIS Beaufils and M-DRIS Jones showed a higher correlation compared to the other methods studied in this work. The DRIS has been appointed as an alternative to the interpretation of the nutritional state of plants using dual relationships between nutrients, with the advantage in the fact that it minimizes the effects of dilution and concentration. While levels and critical ranges are univariated and bivariated on DRIS, the CND is a multivariated diagnosis method, which index, when tending to 0 shows a higher nutritional balance. The ChM, DRIS and CND methods proved to be promising for the calibration of optimal nutrient contents for the sugar cane crop, based on data coming from nutritional monitoring of commercial lots of sugar cane. However, the optimum nutritional contents obtained by these methods for most nutrients were below the recommended in the literature.

Diagnose nutricional e potencial de resposta a adubação em cana-de-açúcar (Saccharum spp.) na região de Tabuleiros Costeiros em Alagoas.

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