Modelling of functions in calculating DRIS indices.
Wadt P. G. S., Silva D. J., Maia C. E., ToméJúnior J. B., Pinto P. A. da C., Machado P. L. O. de A.
Author Affiliation: Embrapa Acre, Caixa Postal 321, CEP 69908-970 Rio Branco, AC, Brazil.
Pesquisa Agropecuária Brasileira 42 : 57-64
Abstract : DRIS functions and k factor were used for the foliar diagnosis of mango from 10 commercial orchards, at yield stage, in the São Francisco River valley in Brazil during 1998-99. Monthly data on leaf N, P, K, Ca, Mg, B, Fe, Mn, Zn and Cu concentrations were recorded. Data tested for normality and bivariate relationships between nutrient concentrations were used to calculate the DRIS indices. Mean, variance as well as minimum and maximum values were calculated for each relationship within the population. The nutrients were classified as highly responsive macronutrients (HRMa) (N, P and K); rarely responsive macronutrients (RRMa) (Ca and Mg); highly responsive micronutrients (HRMi) (B, Fe, Mn and Zn), and rarely responsive micronutrients (RRMi) (Cu). DRIS functions were developed for each nutrient class. The results showed that the developed model expresses the nutritional balance adjusted for each nutrient, and reflects the expected biological behaviour of plants as a result of variation in the availability of nutrients.