Diagnóstico nutricional foliar e blends de fertilizantes de eficiência aumentada em cafeeiros em produção

Abstract

The adoption of technologies for the balanced mineral nutrition of arabica coffee represents an important role to support the productivity of the crop as well as the sustainability of the coffee grower in the agricultural activity. In this sense, the use of portable equipment to diagnose the nutritional status and sources of fertilizers of increased efficiency were evaluated in order to optimize the nutritional diagnosis of arabica coffee and increase the efficiency of use of nutrients for the culture. Therefore, the aim of the first article was to determine the levels of nutrients N, K and Ca in the coffee leaf extract, with a portable ion-selective device, correlating them with the levels determined in the leaf by the acid digestion method, the in order to obtain an efficient and fast-response methodology. The work was carried out in commercial crops in the production phase, divided between cultivars of Coffea arabica L. (Catuaí-IAC99 and Acaiá IAC 474-19), in two trials: one involving the standard management of the farm and the other with varying doses of nitrogen. The results showed a significant Pearson correlation for Ca and K between the cultivars Acaiá IAC 474-19 and Catuaí IAC 99, with a high correlation for Ca, indicating, in a first evaluation that, that for this nutrient, the technique has a good tendency to use supporting new investigations for method validation. There was low correlation for K, probably due to its rapid mobility in the plant. For N, there was no significant correlation between the methods, indicating that the levels of nitrate in the leaf extract do not present adequate concentrations for their correlation with the content of total N. However, depending on the doses of N applied with the two sources (ammonium nitrate and urea), it was observed that the nitrate contents of the coffee leaves adjusted to the quadratic model and did not present significant differences for the effect of the sources. The second article aimed to evaluate the efficiency of blends, through the association of conventional fertilizers, of controlled or slow-release fertilizers, for coffee in production. Five fertilizers were used: two conventional sources - Urea and Ammonium Nitrate, divided into three applications, and three formulations of blends, applied in a single fertilization - Blend 1, Blend 2 and Blend 3, subjected to varying doses of N, K2O and P2O5. The N release for the blend treatments showed different longevity between the use of blends associated with controlled release fertilizers, compared to the slow release. The release of nutrients from blends 2 and 3 were higher in the laboratory, compared to that observed in the field test. Leaf N and P contents were influenced only by the isolated effect of doses. Among the nutrient release tests (in the field and in the laboratory) blend 2 presented itself as the source of greater longevity and adjustment in contrast to the nutritional demand of the coffee tree. The Blend 3 application strategy, in top dressing and incorporated, did not influence the release of nutrients N, P and K. The sources under study, as well as the variation of N, P and K doses, did not influence produtivity, income or yield, output and income or hulling for coffee in its first year of evaluation, demonstrating that medium to long-term studies are needed for the culture to support interference in the production environment for the use of sources and different doses of nutrients N, P and K.