Optimizing nitrogen fraction in the potato crop in the Toluca Valley

Abstract

The more convenient way to fractionate the nitrogen fertilizer varies according to the soil type, crop management and weather conditions. The objective of the present study was to determine the best way to fractionate the nitrogen in the potato crop in the Toluca Valley, under rainfed conditions. In 2006 an experiment was established, where three doses of nitrogen were tested (100, 200 and 300 kg N ha-1) fractionated in 1, 2 and 4 parts that were applied to the sowing, 18, 34 and 47 days after plant emergence (DAE). As well a treatment without nitrogen was included. During the vegetative cycle of the crop, four determinations were made for the nitrate concentration in the cellular extract of the leaf petioles (ELP) at 25, 40, 54 and 68 DAE, a CARDY meter was used. The maximum yields of 42.4 and 42.1 ton ha-1 were obtained with 200 kg N ha-1, when nitrogen was fractioned in one or two part respectively. The nitrate concentration at the ELP at 25 DAE associated with the maximum yield was 1 818 and 1 812 of N-NO3 respectively. The nitrate analysis at the ELP indicated that fractioning into four parts the nitrogen, it propitiate deficiencies of this element during the early stages of the plant development and the late applications caused physiological alterations in detriment of the production of tuber.