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

The effect of the rate and method of nitrogen application on nitrogen uptak e and utilization by broccoli (Brassica oleracea var, italica) was studied in four field experiments. The methods of application were broadcast applic ation vs band placement and split application. Maximum uptake of nitrogen b y the crop was around 300 kg ha(-1). In one experiment band placement posit ively influenced nitrogen uptake. Split application did not influence nitro gen uptake. Nitrogen application resulted in a higher head dry matter produ ction, but the efficiency of nitrogen utilization for the production of hea d dry matter decreased with higher amounts of nitrogen applied. Nitrogen ap plication decreased the dry matter content of the heads. In half of the exp eriments band placement of nitrogen fertilizer resulted in extra head dry m atter production and lower head dry matter contents. At the optimum rates o f band placed nitrogen application, the nitrogen harvest index in the exper iments ranged from 27 to 30 percent. The amount of mineral nitrogen in the soil at harvest generally increased w ith 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 wi th increasing amounts of nitrogen applied, but was always less than the amo unt of nitrogen in crop residues. At the optimum rates of band placed nitro gen application, the amount of nitrogen in crop residues ranged from 120 to 155 kg ha(-1). With broccoli cultivation, the nitrogen in the crop residue s forms the single largest source of potential loss of nitrogen to the envi ronment.