氮肥种类及用量对油菜硝酸盐累积的影响

施用氮肥能明显增加油菜硝酸盐累积；且存在油菜硝酸盐累积随施氮量增加而明显增加的趋势。无论高量、低量水平：施用硝酸铵使油菜硝酸还原酶活性受到较强的抑制，从而累积的硝酸盐最多；施用尿素，油菜硝酸还原酶活性较强，累积硝酸盐较少。施用硝酸钙，油菜硝酸还原酶活性虽不很强，但由于其中的钙可促进油菜对氮素的同化，所以硝酸盐的累积也较少。施用低量硫酸铵，油菜累积硝酸盐较少；而施高量硫酸铵，则累积较多。

Effect of the Varieties and Rates of Nitrogen Fertilizer on Nitrate Accumulation in Rape

The results showed that supplying nitrogen fertilizer could increase the nitrate accumulation in rape sharply, and Rape's nitrate accumulation increased with fertilization increasing. According to ether of the two Nitrogen Fertilizer rates: supplying Rape with Ammonium nitrate, rape's Nitrate Reductase Activity (NRA) was restrained strongly, so rape's nitrate accumulation was very high; while supplying Rape with Urea, rape's nitrate accumulation was comparatively low because their NRA was comparatively strong. When Rape supplied with Calcium nitrate, though nitrogen fertilizer provided was in form of NO3- totally and rape's NRA was not strong enough, its nitrate accumulation was lower than that with the supplying of Ammonium nitrate because of the influence of Calcium. If Ammonium Sulfate supplied, when the supplying rate was lower, Rape's nitrate accumulation was lower than any one of the rest lower nitrogen treatments ; while the rate was higher, its nitrate accumulation was comparatively high.