Relación entre nitrógeno foliar y el contenido de clorofila, en maíz asociado con pastos en el Piedemonte Llanero colombiano

In the piedmont of Colombia, an association between maize and the grasses Brachiaria decumbens Stapf., Brachiaria Mulato hybrid, Brachiaria brizantha cv. Toledo was established as a means of renewing a degraded pasture, using a nitrogen fertilization of 100 and 200 kg ha-1. To estimate the leaf nitrogen in the maize and grass, we compared the laboratory kjeldahl method and the measurement of the greenness index using a clorofilometro, Minolta SPAD® 502 (rapid nondestructive method). The evaluation at the beginning of flowering in the maize (35 days after planting) had a coefficient of determination (r2) of 0.79 in the maize and in the grass, while at the beginning of grain filling (60 days after planting) an r2 of 0.92 was recorded in the maize and 0.96 in the grass, indicating a good relationship between leaf N and the clorofilometro greenness index. At doses of 200 kg ha-1 N, the chlorophyll content was significantly higher with 51.6 SPAD units in the leaves of the corn, but grain yield was similar between 100 and 200 kg ha-1 N with a yield of 5.2 t ha-1.