Effect of Different Fertilization Pattern on Available Nitrogen Dynamics in Tobacco Planting Soil in Southwest Hubei

A field experiment was carried out in tobacco planting soil in southwest Hubei to study the effect of different fertilization pattern on available nitrogen dynamics.The results showed that,in years of high rainfall,nitrogen from chemical fertilizers completely leached out within one month after tobacco transplanting.Nitrogen from organic fertilizer in 0-20 cm soil supplied nitrogen to tobacco within 45-70 d after transplanting.Soil organic nitrogen started to mineralize,which increased soil available nitrogen contents 60 d after transplanting.Chemical nitrogen largely leached out under uncover condition and soil available nitrogen increased if using plastic cover.Applying nitrogen fertilizer earlier can cause chemical nitrogen to transfer to organic nitrogen,thus reduce the risk of nitrogen leaching greatly.