Rendimiento de brocoli (Brassica oleracea L. var italica) bajo diferentes dosis de nitrogeno y fosforo en un suelo aluvial de Linares.

In the period from January to April 1992 on an alluvial soil, a trial was carried out, to determine the effects of different nitrogen and phosphorus rates and their interactions on yield of broccoli and their possible effects, at harvest, on different parameters of the plants. The trial was done as a 4 x 4 factorial experiment in a complete random block design, using a combination of 4 nitrogen rates (0, 80, 160 and 240 kg/ha) and 4 phosphorus rates (0, 40, 80 and 120 kg/ha), evaluating the effect of 16 fertilizer combinations on yield and plant characteristics. At harvest, 10 plants complying a density of 61.538 plants/ha were evaluated, obviating plants from borders, corresponding to each of the treatments. Harvest was made by cutting the central inflorescence on the insert of the first lateral bud; lateral buds were harvested until they had a commercial production. The following agronomical characteristics were analyzed: inflorescence yield (central, lateral and total), central inflorescence parameters (stem diameter and inflorescence diameter, inflorescence weight, and hollow stem), and lateral inflorescence parameters (inflorescence diameter and weight). Results were analyzed by Fisher's variance and the significance among parameters was estimated by Tukey's test. Also simple correlations were calculated among the different parameters. A favorable effect of nitrogen rates on central inflorescence was observed. Phosphorus effect was mainly on lateral inflorescence. Nitrogen and phosphorus fertilization did not increase in a statistically significant manner the hollow stem percentage, although a significant correlation existed among the main inflorescence weight and hollow stem percentage. In regards to correlations among parameters analyzed, the central inflorescence diameter with its weight presented the highest positive association (r=0.934), and lateral inflorescence diameter with total weight presented the lower association degree (r=0.265). None of the associations was significantly negative.