Adubação com NPK e o estado nutricional de 'citrumelo' por medida indireta de clorofila

Abstract

The SPAD values of the leaves have correlation with nutrients content and dry matter production and could be used for evaluation of the nutritional state in citrus rootstock. The aim of this work was to evaluate the effect of the rates of nitrogen (N), phosphorus (P) and potassium (K) on the indirect measure of chlorophyll in the lemon tree citrus rootstock of citrumelo. After 20 days from sowing of the plants, the experiment was installed, in a randomized design factorial project 3×3 + 1, being three rates of N, P e K (920 mg dm-3, 790 mg dm-3 and 100 mg dm-3, respectively), with three replications. The treatments were: D1 = half of the recommend rate; D2 = the recommend rate; e D3 = two times the recommend rate and one control (without fertilization). Four months after the emergency, were determined the SPAD values, dry matter yield and the N, P and K content of the plants. Interaction between N, P and K content with SPAD values the plants were found. SPAD values with N content and with the dry mass yield of the plants the citrus rootstock were encountered, indicating that the indirect measure of chlorophyll is adequate for the evaluation of the nitrogen content of 'citrumelo' plants.