Effect of nitrogen on growth, flower yield, oil composition, and yield inboronia megastigmanees

Four forms of nitrogen (N), isobutylidene diurea (IBDU), urea, ammonium nitrate (NH4NO3), and calcium nitrate [Ca(NO3)2] were applied to boronia plants at three rates of application (25, 50, and 100 kg N/ha) either as a single application in late October or in two equal applications, one in October and the other in early January. Two sites and two clones were investigated, growth measurements were taken on one site on a regular basis throughout the year, and flowers were harvested in September. Leaf N, flower N number of nodes, and flower and oil yields as well as the percent volatiles and ß‐ionone content of the oil were positively correlated with increased rates of N application. Ammonium nitrate and Ca(NO3)2 gave the highest yields for both clones. IBDU and urea were partially toxic to Clone 5 at 100 kg N/ha which was thought to be due to an inability to detoxify ammonium (NH4) rather than a low nitrate reductase activity. This results of this experiment provides guide lines for N management in the future.