为了研究施肥方式对蕹菜硝态氮累积和土壤酶活性的影响, 在上海郊区一蔬菜园艺场设置了6个施肥处理: 不施肥对照; 施用复合化肥量分别为900, 1 800和2 700 kg/ha; 施用菜籽饼肥量分别为2 250, 4 500 kg/ha, 并定期监测蕹菜硝态氮含量的变化和土壤酶活性的差异. 结果表明: 复合化肥的施肥量越多, 蕹菜硝态氮的累积量就越高, 且肥料施用量与蔬菜硝酸盐含量呈极显著正相关(p<0.01); 在蕹菜的整个生长周期内, 植株的硝态氮含量先上升, 至21 d左右达到最大值, 然后迅速减少, 至54 d 后趋于平稳, 且在可食用范围内; 不同施肥处理的蕹菜在生长后期, 其土壤脱氢酶、过氧化氢酶、脲酶和酸性磷酸酶的活性均显著高于施肥前的背景土壤, 说明蕹菜生长有利于增加土壤酶活性. 施菜籽饼肥的土壤酶活性显著高于施复合化肥, 说明增施有机肥可提高土壤酶活性.

To study influences of different fertilizing patterns on nitrate accumulation in swamp cabbage and soil enzyme activity, a field experiment was carried out in the suburb of Shanghai. It includes six different fertilizer treatments: no-fertilizer control; synthetic chemical fertilizer at 900, 1 800 and 2 700 kg/ha respectively; rapeseed cake manure at 2 250 and 4 500 kg/ha respectively. Content of nitrate in the vegetable and the activity of soil enzymes were analyzed throughout the growth period. The results as follows. (1) The more the applied chemical fertilizer, the higher content of nitrate is accumulated in thevegetable. The nitrate content in the vegetable has significant positive correlation with the amount of chemical fertilizer application (p<0.01). (2) During the entire growth period,
the nitrate content in the vegetable increases quickly at the beginning, reaches maximum after 21 days, then declines sharply and maintains a stable and edible range after 54 days. (3) During the latter stage of growth, activities of soil enzymes including dehydrogenase, catalase, urease and phosphatase are all significantly higher than those of the background soil, suggesting that the vegetable growth improves soil enzyme activities. Moreover, activities of soil enzymes with cake manure treatments are significantly higher than those with treatments of synthetic chemical fertilizer, suggesting that application of organic manure
can increase the enzyme activities more significantly.