The effect of the rate and method of nitrogen application on nitrogen uptake and utilization by broccoli (Brassica oleracea var. italica)

Abstract

The effect of the rate and method of nitrogen application on nitrogen uptake and utilization by broccoli (Brassica oleracea var. italica) was studied in four field experiments. The methods of application were broadcast application vs band placement and split application. Maximum uptake of nitrogen by the crop was around 300 kg ha-1. In one experiment, band placement positively influenced nitrogen uptake. Split application did not influence nitrogen uptake. Nitrogen application resulted in a higher head dry matter production, but the efficiency of nitrogen utilization for the production of head dry matter decreased with higher amounts of nitrogen applied. Nitrogen application decreased the dry matter content of the heads. In half of the experiments, band placement of nitrogen fertilizer resulted in extra head dry matter production and lower head dry matter contents. At the optimum rates of band placed nitrogen application, the nitrogen harvest index in the experiments ranged from 27 to 30%. The amount of mineral nitrogen in the soil at harvest generally increased with increasing amounts of nitrogen applied. Band placement resulted only in one experiment in lower amounts of mineral nitrogen in the soil at harvest. The mineral nitrogen in the soil at harvest can be unevenly horizontally distributed, both with broadcast application and band placement of nitrogen fertilizer. The amount of nitrogen unaccounted for at harvest increased with increasing amounts of nitrogen applied, but was always less than the amount of nitrogen in crop residues. At the optimum rates of band placed nitrogen application, the amount of nitrogen in crop residues ranged from 120 to 155 kg ha-1. With broccoli cultivation, the nitrogen in the crop residues forms the single largest source of potential loss of nitrogen to the environment.