Effects of Nitrogen Application Rate on Yield,Quality and Nitrogen Efficiency of Winter Potato
A field experiment was carried out to investigate the effects of nitrogen application rate(0,120, 180, 240, 300, 360 kg N/hm2) on the growth, yield, nitrogen efficiency and quality of winter potato in Pearl River Delta area. The results showed that chlorophyll content, leaf area, height and stem diameter under 180-300 kg N/hm2were better than those under other treatments, the yield and economic effectiveness of 240 kg N/hm2was the highest. N harvest index and apparent N recovery efficiency was between 0.57-0.66 and 12.65%-28.13%, respectively, and they decreased with the nitrogen application rate increased. However, the agronomic N use efficiency and physiological N use efficiency were enhanced with nitrogen application rate increased and peaked at 240 kg N/hm2with the highest value of 55.56 kg/kg and 48.07 kg/kg, respectively. The content of crude protein and soluble sugar of potato tuber increased with nitrogen fertilizer application rate increased and peaked at180 kg N/hm2and 120 kg N/hm2, respectively. However, the nitrogen application rate had no significant effect on vitamin C and starch content. It is suggested that 240 kg N/hm2application on winter potato in Pearl River Delta area is advisable.