NITROGEN, PHOSPHORUS, AND POTASSIUM IN SPAD READINGS IN RANGPUR LIME ROOTSTOCK

Abstract

The objective of the experiment was to evaluate the effect of N, P, and K rates on the chlorophyll indirect measurement in the rangpur lime rootstock. Twenty days after the rangpur lime rootstock sowing, the experiment was installed in a complete randomized factorial scheme 3³ + 1, with three factors (NPK) in three levels and a control (without fertilization), with three repetitions. The treatments consisted of half of the standard dose, the standard dose, two times the standard dose, and no fertilization. Four months from the emergence of the rangpur lime rootstock, the SPAD (Soil Plant Analysis Development), dry matter, and nitrogen concentration were determined. N affected SPAD readings, while P and K did not affect. The effect of N in the SPAD reading was influenced by the application of P. There was a positive correlation between the SPAD reading and the N concentration and with the dry matter production. The use of the chlorophyll indirect measurement method  is appropriate for evaluating the N nutricional state of the rangpur lime rootstock

KEY-WORDS: Citrus limonia; plant nutrition; nutritional diagnosis; SPAD.