Métodos de diagnose nutricional da cana-de-açúcar fertirrigada na Paraíba

Abstract

Sugarcane was introduced in Brazil in the early sixteenth century, where it found favorable natural conditions, being today one of the main Brazilian agribusiness crops. Brazil is the world's largest producer of the crop, but still has average productivity considered low. Irrigation is one of the techniques that has been used to improve these productivity values, and drip irrigation has been highlighted by its high efficiency in water use and the possibility of fertilizing the crop via fertirrigation. This technology has been expanded in the sugar cane producing units in order to achieve higher yields and the longevity of the cane field. However, the nutritional demand of the fertirrigated crop is different from the one cultivated in the rainfed. With this, there is a lack of information to better guide the nutritional management of the crop in this type of system. The nutritional diagnosis of the plants can be made with the aid of foliar diagnostic methods such as DRIS, M-DRIS and CND. The first step in implementing a nutritional diagnostic system is the establishment of standard values or standards. The use of regional or specific standards increases the accuracy of the methods used to make a diagnosis of the nutritional status of crops. Thus, the objective of this work was to perform the nutritional diagnosis for the fertirrigated sugar cane via the DRIS, M-DRIS and CND methods, based on specific norms generated for each method used. For this, samples of leaf +1 samples were collected from 26 plots cultivated with sugarcane in the drip fertirrigation system at the Japungu Distillery in Paraíba. The contents of N, P, K, Ca, Mg, S, Cu Fe, Mn, Zn, B, Mo and Ni were calculated on the leaves and, together with the productivity data recorded in the sampled areas, a database was formed that was used to generate DRIS, M-DRIS and CND standards. The nutritional diagnosis of the crop was performed by the three methods and the interpretation performed by the method of potential response to fertilization (PRA). The agreement of the diagnosis was evaluated by the different methods studied. The diagnosis performed by DRIS and M-DRIS indicated Mo as the main limiting nutrient, and Fe as a potentially excess nutrient. The nutritional diagnosis by the CND method interpreted by the PRA disagreed with the DRIS and M-DRIS methods and indicated imbalance of micronutrients and K deficiency. The methods proposed by this study can be adopted for the nutritional diagnosis and the calibration of optimal contents for the culture of fertirrigated sugarcane, effectively contributing to the monitoring of commercial crops.