Efecto del nitrógeno disponible sobre los componentes del balance de nitrógeno en un cultivo de coliflor ("Brassica oleracea" var. "Botrytis")

Abstract

There is increasing interest in crop nitrogen fertilization optimization and thus the improvement of nitrogen use efficiency to both obtain high yields and reduce the side effects related to nitrogen leaching. The objective of this study was to investigate the effect of the available nitrogen on yield and the nitrogen use efficiency in a cauliflower crop (Brassica oleracea var. Botrytis) var. Barcelona with a growing cycle of 75 days. The trial took place in Finca Valdegón, at the SIDTA of Gobierno de La Rioja, in Agoncillo, Spain in 2012. Planting was carried out in August. A completely randomized experiment with four nitrogen treatments and four replications each was designed: T1 (Nmin initial), T2 (190 kgN/ha), T3 (270kgN/ha), T4 (320 kgN/ha). Based on soil analysis, fertilizer was applied as follows: T1: 0 kg N/ha; T2: 87 kgN/ha; T3: 149 kgN/ha; T4, 194 kgN/ha. Ion exchange resins were installed in tubes at 0.2 m depth to estimate mineralization in all experimental plots. Soil and plant samples were collected periodically for nitrogen content determination as well as nitrate in the resins and plant biomass. Yield was related to the total available nitrogen but above 224 kg N/ha yields did not exceed 23 t/ha. Average mineralization at 0.3 m deep from transplanting to harvest was estimated at 41 kgN/ha. The relationship between nitrogen content and nitrogen available in leaves and heads was studied. Excess fertilizer led to further losses thereof, thus decreasing the available nitrogen use efficiency.