Testing and validation of DRIS for apple tree Calibração e validação do DRIS para macieira

To evaluate three procedures of the calculation of DRIS indices, as well as the efficiency of DRIS as a method for the interpretation of apple tree leaf analyses. This study uses data collected in apple producing areas of the Rio Grande do Sul and Santa Catarina States, Brazil. The concentrations of nitrogen, phosphorus, potassium, calcium, magnesium, boron, copper, iron, manganese, and zinc were determined in the leaf samples. The validation of the DRIS method used results of an experiment of potassium fertilization. The DRIS indices were calculated using two criteria for the choice of the ratio order of nutrients (F value ratio of variance of the relationships among nutrients between the reference group and the low productivity group, and R value - correlation coefficients between the productivity and the relationship between pairs of nutrients) and three forms of calculation of nutrient functions (methods of Beaufils, Jones and Elwali & Gascho). The Nutritional Balance Index (NBI) presented negative correlation with the productivity in all combinations. The DRIS method described by Elwali & Gascho, using the F value, presented a performance similar to the criterion of sufficiency range, and it can be used for the interpretation of foliar analysis of apple trees, because it presents values of the nutritional balance index that indicates the nutritional status of the plants, and for the efficiency in the nutritional diagnosis of the crop.<br>Este trabalho teve por objetivo avaliar três procedimentos de cálculo dos índices DRIS, bem como avaliar a eficiência do DRIS como método de interpretação de resultados de análises de folhas de plantas de macieira. O estudo foi realizado nas regiões produtoras de maçã do Rio Grande do Sul e de Santa Catarina. Foram determinadas as concentrações de nitrogênio, fósforo, potássio, cálcio, magnésio, boro, cobre, ferro, manganês e zinco nas amostras de folhas. A validação do método DRIS utilizou resultados de um experimento de adubação potássica. Os índices DRIS foram calculados utilizando-se dois critérios para a escolha da ordem da razão dos nutrientes (valor "F" - razão de variância das relações entre nutrientes entre o grupo de referência e de baixa produtividade e valor "R" - coeficientes de correlação entre os valores de produtividade e a relação entre os pares de nutrientes) e três formas de cálculo das funções dos nutrientes (métodos de Beaufils, Jones e Elwali & Gascho). O Índice de Balanço Nutricional (IBN) apresentou correlação negativa e significativa com a produtividade em todas as combinações de métodos testados. O método DRIS descrito por Elwali & Gascho, utilizando o "valor F", apresentou desempenho semelhante ao critério de faixa de suficiência e pode ser utilizado para a interpretação da análise foliar em macieira, por apresentar valores de IBN que indicam o estado nutricional das plantas e pela eficiência no diagnóstico nutricional da cultura

Recommendation of soil fertility levels for willow in the southern highlands of Santa Catarina

The species Salix x rubens is being grown on the Southern Plateau of Santa Catarina since the 1940s, but so far the soil fertility requirements of the crop have not been assessed. This study is the first to evaluate the production profile of willow plantations in this region, based on the modified method of Summer & Farina (1986), for the recommendation of fertility levels for willow. By this method, based on the law of Minimum and of Maximum for willow production for the conditions on the Southern Plateau of Santa Catarina, the following ranges could be recommended: pH: 5.0-6.5; P: 12-89 mg dm-3; Mg: 3.2-7.5 mg; Zn: 5.0-8.3 mg dm-3; Cu: 0.8-4.6 mg dm-3; and Mn; 20-164 mg dm-3. The Ca/Mg ratio should be between 1.2 and 2.9. For K and Ca only the lower (sufficiency level), but not the upper threshold (excess) was established, with respectively 114 mg dm-3 and 5.3 cmol c dm-3. It was also possible to determine the upper threshold for Al and the Al/Ca ratio, i.e., 1.7 cmol c dm-3 and 0.28, respectively. For maximum yields, the clay in the soil surface layer should be below 320 g dm-3