植物体氮素的挥发损失——Ⅱ.植物收获期地上部分氮素减少与土壤、作物和肥料供应的关系

试验表明,从整体来看,小麦的地上部分氮素在成熟期明显减少,而豌豆则无,至少采用差数法看不出其损失。氮素损失数量与土壤供氮水平有关。供氮较充分时,损失少;供氮不足时,损失反而严重。在缺磷严重的土壤上施用磷肥,豌豆后期地上部分的氮素反有减少;在其他情况下,则有所增加。施磷肥有助于小麦成熟期地上部分氮素的增加,施氮磷则可使其明显降低。在供氮较高土壤上施用氮肥,小麦后期氮素减少;在供氮较低的土壤上则相反。施肥对增产的影响取决于对其植株体内的含氮百分率影响的大小。施肥后,小麦前期含氮百分率高者,后期氮素总量均降低,反之则增加。

Nitrogen Loss from Plants by VolatilizationIt. The Relationships Among Nitrogen Reduction from Above-ground Plants at Maturity and Soils, Crops as Well Fertilization

Pot experimemt results show that on the whole, the nitrogen in wheat was significantly reduced during maturity period while pea had no such reduction, at least the loss could not be determined by the method used in the experiments. The nitrogen amounts lost from plants were related to the soil N-supplying levels: the loss was less when the supplying level was high. Otherwise it was high due to wheat early senility. Applying P fertilizer to the soil seriously deficient in available P, the nitrogen in pea was reduced at maturity. However, in other cases, nitrogen was increased. Application of P fertilizer assisted nitrogen increase in aboveground parts of wheat at maturity. In contrast, application of N and P fertilizers led to its reduction significantly. Applying N fertilizer into a soil with low N-supplying capacity, nitrogen in plants was increased at late growth stage. It seemed that the influence of fertilization on the nitrogen loss from plants depended on the N contents of wheat plants.- the total N uptake by plants was reduced by application of fertilizer if nitrogen percentage was high in plants at early stage. However, the reverse was true for the plants with low nitrogen contents at early stage.