Study On Nitrogen Leaching Regulations On Three Textures Of Soil

Nitrogen fertilizer is one of the most important fertilizers used in forest management. Due to unreasonable management, the ratio that plant takes the fertilizer is low although a large amount of fertilizer is applied, the loss of nitrogen is still very high, and leaching is one of the most important ways of nitrogen losing. Transportation of nitrogen in the soil is effected mainly by the amount of fertilizer, precipitation, soil texture, study the leaching regulations of soil under different amount of fertilizer applied can provide envidence for reasonable fertilizing, on one hand, it can reduce the loss caused by soil leaching after fertilizing, on the other hand, it can avoid pollution by preventing nitrogen from leaching down to underground water.This study used a column method and sitimulated rainfall to determine the nitrogen leaching of different textures of soil, and the results were as follows:1. Nitrate is the main nitrogen leaching form, in this study over 60% of nitrogen leached as nitrate in 3 types of soil, while the proportion of ammonium was under 15%.2. The amount of fertilizer applied to the soil was one important factors influnced the nitrogen leaching, the amount of leaching increased while the fertilizer increased, and the equation of total nitrogen leaching amount and fertilizer amount can be described as follows: sandy soil:y=0.4261x+127.83 (R2=0.9606) loam soil:y=0.2508x+220.67 (R2=0.9297) clay soil:y=0.5994x+58.937 (R2=0.9299).3. Precipitation was another factor influced the nitrogen leaching. It would cause leaching easily under the condition that there were no plants or the fertilizer was much sufficient to the plant. This study showed the equation between total nitrogen leaching amount and precipitation amount.4. The results showed that, in sandy soil, fertilizing would not cause leaching at 20cm while the amount of fertilizer is under 100 kg·hm-2, when it reaches to 200 kg·hm-2, fertilizing would not cause leaching at 60cm; in loam soil, fertilizing would not cause leaching at 20cm while the amount of fertilizer is under 200 kg·hm-2; while in clay soil, fertilizing would not cause leaching at 40cm while the amount of fertilizer is under 100 kg·hm-2. When roots are within certain depth and the amount of fertilizer is under certain amount, nitrogen leaching caused by fertilizing would be neglected.