Abstract

Many methods of nutritional diagnosis present discordant reports. It is necessary to study how these diagnoses relate to agricultural productivity and nutrient balance for a more efficient nutritional monitoring of the crops. This study had two objectives: (1) evaluate and compare Diagnosis and Recommendation Integrated System (DRIS) and Compositional Nutrient Diagnosis (CND) methods for nutritional diagnosis of sugarcane cultivated in the Northeast of Brazil; (2) establish standards, identify and hierarchize nutritional limitations. The database consisted of 183 samples, in which 31 were in areas with high productivity (³ 80 Mg ha^-1) and 152 of areas with low productivity (< 80 Mg ha^-1). Sugarcane leaves were collected and contents of N, P, K, Ca, Mg, S, Fe, Zn, Cu, Mn and B were determined. The DRIS indexes were calculated by methods DRIS-Beaufils, DRIS-Jones, DRIS-Elwali and Gascho, M-DRIS Beaufils, M-DRIS Jones, and the indexes CND too were calculated. The DRIS-Beaufils, DRIS-Jones, M-DRIS Beaufils and M-DRIS Jones methods tended to agree on the nutritional diagnosis of sugarcane. The nutritional diagnosis of the CND method interpreted by the Potencial Fertilization Response (PFR) was different from the DRIS methods for N and Mn nutrients. The M-DRIS Beaufils and M-DRIS Jones methods showed a higher correlation with nutrient contents. However, there was no significant correlation between agricultural productivity and nutrient balance index mean (NBIm), suggesting that other factors influenced sugarcane production more than nutritional factors. The nutritional diagnosis methods identified excessive fertilization with N and limitations of Ca, Mg, K, S, Mn, Cu, Zn and B in sugarcane in the Northeast of Brazil.

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