Diagnose nutricional da videira cultivada no Vale do Submédio São Francisco

Abstract

Grape (Vitis vinifera L.) is a highly profitable crop, one of the most important fruit crops in Submédio São Francisco Valley. The assessment of nutritional status of the vine is important because it influences yield and quality of grape. Despite this, specific nutritional standards for the grape in the region have not been developed yet. Integrated Diagnosis and Recommendation System (DRIS), modified DRIS (M-DRIS), and Composition Nutrient Diagnosis (CND) are modern methods of nutritional diagnosis that consider the interactions among nutrients and can be used to stablish nutritional standards in Submédio São Francisco Valley. Also, the relationship between nutritional balance and content of Ca bound to pectins in the cell wall (Ca-pectin) has not yet been evaluated. Ca is the nutrient that most interferes with the quality of the fruit, being related to fruit firmness and fruit quality in post-harvest. Thus, the objectives of this study were: to define specific DRIS, M-DRIS, CND norms for grapes in Submédio São Francisco Valley; evaluate and compare nutritional status of grape using these methods in three different production environment; evaluate the relationship of Ca-pectin with DRIS, nutrients concentrations (soil, leaf and fruit) and criteria of fruit quality. The work involved three cultivars produced in the region (BRS Vitória, Sweet Jubilee and Sugar Crisp), grown in three different environments, at PL (Petrolina / PE), JZ (Juazeiro / BA), and CN (Casa Nova / BA) farms. Twenty vineyards were selected and soil, leaf and fruit samples were collected to determine N, P, K, Ca, Mg, S, Fe, Cu, Mn, Zn and B concentrations. Database was divided into two populations (high and low-yielding). As a criterion for separating populations, the average yield + 0.5 of the standard deviation was used, with 18.89 Mg ha-1 being the limit for separating them. DRIS standards were developed from the selection of dual ratios between nutrients that had the highest variance ratio between low and high-yielding populations. The respective DRIS, M-DRIS and CND nutrient indices and the Average Nutritional Balance Index (IBNm) of each vineyard were calculated. The results were interpreted by Response Potential to Fertilization (PRA). Fruits were evaluated for berry weight and diameter, bunch length, soluble solids, titratable acidity and berry firmness. Fe, Cu and Zn compromised the normality of some dual relationships. The nutritional diagnosis methods showed high percentage of agreement, suggesting that the use of any of them may be recommended for the region. Nutritional diagnosis carried out by DRIS identified Mn deficiency and excess Ca in vineyards, showing nutritional imbalance in 73% of nutrients. Grape yield was negatively correlated with IBNm, suggesting that grape yield has been influenced by nutritional imbalance. Ca-pectin showed negative correlation with IBNm, indicating that nutritionally unbalanced plants have higher Ca-pectin content. Ca-pectin was positively correlated with TA and did not correlate with berry firmness. Principal component analysis showed that Ca-pectin was correlated with nutrients in the fruit and dry weight, but not with nutrients in the soil and leaf. Fertilization programs need to be monitored and readjusted to optimize fruit yield and quality.