Establishment of leaf nutrient patterns for the nutritional diagnosis of Urochloa brizantha pastures in two seasons

ABSTRACT. To diagnose and monitor the nutritional status of commercial crops, reference standards must be established based on chemical analyses of soils and leaf tissues. Therefore, the objective of this study was to establish sufficiency ranges, DRIS standards and leaf nutritional diagnoses for palisade grass pastures in the rainy and dry seasons. Of a total of 105 sampled pastures, the 20 highest-yielding areas were used to establish reference standards. In the other, low-productivity pastures, the nutritional status was diagnosed in both the rainy and dry seasons for nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), boron (B), copper (Cu), iron (Fe), nickel (Ni), molybdenum (Mo), and zinc (Zn). A productivity of 15 tons ha-1 year-1 was determined as the threshold to separate high-yielding (> 15 tons ha-1 year-1) pastures from low-productivity pastures (< 15 tons ha-1 year-1). Sufficiency ranges and foliar DRIS standards were established for palisade grass pastures in the rainy and dry seasons, which resulted in the recommendation of region- and season-specific sufficiency ranges and DRIS leaf standards. In the rainy season, in more than 50% of the evaluated pastures, nutritional deficiencies in all nutrients except K, B and Zn were observed, while in the dry season, only N, P, Cu, and Mn were deficient.