Saturday, 15 July 2006

Leaf Sampling Period Effect on the Efficiency of the DRIS Method Applied to Apple Culture in South Brazil.

Gilmar R. Nachtigall, Embrapa Grape and Wine, Rua Livramento, 515 P.O. Box 130, Bento Gonçalves - RS, Brazil and Antonio R. Dechen, Escola Superior de Agricultura "Luiz de Queiroz", Av. Padua Dia , 11, Piracicaba - SP, Brazil.

Nowadays, Brazil has about 30,000 hectares of apple orchards distributed mainly in the southern region. The Diagnosis and Recommendation Integrated System (DRIS) has successfully been developed and proposed by researchers for several annual and perennial crops including fruit cultures. One main advantage of DRIS is the ability to minimize the leaf age effect, allowing obtaining leaf samples from a larger tissue age range than the critical value do. The DRIS norms, once established for a particular crop, can be applied to the same crop in any other region. Little information concerning DRIS method application to apple orchards is available for the Brazilian conditions, especially about the effect of leaf sampling period on DRIS indices. Therefore, the objective of this research was to evaluate the DRIS method efficiency for different leaf sampling periods in Brazilian apple orchards. This study was carried out in 70 apple orchards selected for their productivities and management techniques' characteristics, at the following apple producing regions: ‘Campos de Cima da Serra', State of Rio Grande do Sul; and ‘Alto Vale do Rio do Peixe' and ‘Planalto Serrano', State of Santa Catarina. Leaf nutrient concentrations (nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, boron, copper, iron, manganese and zinc) were determined in leaf samples, collected during November, 2004 and February, 2005. DRIS indices were calculated using previously established DRIS norms for these apple orchards, using information from two harvests and leaf sampling in: (1) November 2004 (after the 8th week after blooming); and (2) February 2005 (between the 14th and and 18th week after blooming). Results indicated that leaf nutrient concentrations varied with the leaf sampling period: higher N, P and Cu leaf concentrations were found in samples collected in November/2004; and higher Ca, Mg, S, Fe, Mn and Zn leaf concentrations were found in samples collected in February/2005. DRIS indices calculated with the results obtained in November/2004 were more efficient for the nutritional diagnosis of apple orchards in the southern Brazil, due to the lower variability in leaf nutrient concentrations and better relationship between IBN and productivity.

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