Leaching and transforming characteristics of urea-N added by different ways of fertigation

Soil column method was used to study the characteristics of the movement, transformation, and leach of urea-N in soil added by different ways of the fertigation. The result shows that the amount water added and the way of supplying water and fertilizer were two key factors to affect the movement, transformation, and leach of urea-N in soil. The amount of nitrogen leached was increased with the increasing amount of water applied. And compared to the treatment of fertilizer added as flooding irrigation (FIF), the treatment of fertilizer added in drip irrigation (DIF) significantly decreased the nitrogen leached. The main form of N leached was urea-N, next was NO3--N; the proportion of NH4+-N leached was very low. The NH4+-N accumulated in the upper layer of soil when the irrigation water was low; and at the high irrigation rate, this accumulation was decreased. With the low irrigation water, the content of NO3--N was lower in the upper layer of soil, and higher in deeper layers. As the increase of water added, the level of NO3--N in soil was decreased. It is concluded that, in comparison with FIF, DIF significantly decreased the leaching loss of urea-N from soil, and increased the available N in soil.