Study on Leaching Characteristics of Nitrogen in the Main Types of Tobacco-planting Soils in Nanxiong, Guangdong Province

A soil column experiment was conducted to investigate the leaching characteristics of nitrogen at different nitrogen rates in three main types of tobacco-planting soils in Nanxiong,Guangdong province.The results showed that the main leaching nitrogen form was nitrate in these three types of tobacco-planting soils,leaching occurred mainly in the first 2,3,4 times leaching,and leaching loss volume of nitrate(Y) increased with increasing rate(x) of nitrogen application Ypurple soil=1.8889+0.0121x+0.0012x2(R2 =0.9993),Yliver soil=2.7918-0.0771x+0.0012x2(R2=0.9861),Ysand field=3.6654-0.0536x+0.0012x2(R2=0.9935).In the same amount of nitrogen application,the nitrate leaching rates of three types of soil were as follows: purple soilsand fieldliver soil.The best regression equation between nitrate cumulative leaching loss and leaching times was logarithmic equation.After leaching,the nitrate content in each layer of soil column treated with nitrogen was higher than those without nitrogen application,and in the same nitrogen application rate,the level of residual nitrate in each layer of liver soil column was the highest,but lowest in purple soil.