| Water and nutrient deficiencies are two key factors of limiting the development of agriculture in the dry land. Many of the researches carried out have concentrated on how to apply water and nutrients effectively to achieve the goal of high yield, good quality and high efficiency. Adding fertilizers through the irrigation water (i.e. fertigation) is one of common ways of fertilization. However, the uneven distribution and leachings of nutrients and induced crop damage are the common problems for the traditional way of fertigation. Fertigation by drip irrigation as an advanced technology to control the supply of water and nutrients has been applied by other countries in recent years. However, the movement and transformation of N in soil under fertigation remains unclear. The methods of simulation experiment and culture experiment were used to study the movement and transformation of N in soil under fertigation by drip irrigation. The main experimental results were shown as folio wings:(1) The water infiltration under drop irrigation is a point infiltration; and the soil moisture in vertical and horizontal directions was increased with the irrigation time, and the movement rate were decreased with the irrigation time. And compared to the vertical wetting front, the rate of horizontal wetting front was 1.22 times higher. Different models were used to fit the movement of wetting front, it is found that the polynomial function was a good model. We also use polynomial function to model the soil moisture under drip irrigation; and the function will be useful for design the drip irrigation system and fertigation system.(2) The amount water added and the way of supplying water and fertilizer were two key important 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 NCV-N; the proportion ofNH4+ 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 soil layers. As the increase of water added, the level of NO3-N in soils was decreased, In comparison with FIF, it is concluded that DIF significantly decreased the leaching loss of urea-N from soil, and increased the available nitrogen in soil.(3) The amount of nitrogen leached was in the decreasing order as NO3-fertilizer> urea>NH4+-fertinzer, and the main form of N leached was the N fertilizers added. The amount of nitrogen leached from sand soil exceed in that from clay soil. Applying NH4+-fertilizer can significantly increase the content of NH4+-N in soils, and as the processing of nitrification the content of NH4+-N was reduced, and NO3--N was increased gradually. After applying the urea, the content of NH4+-N in soils reached up to the peak in the fifth day or so, then began to decrease because of the occurring of the nitrification. The content of mineral nitrogen content (NH4+-N + NO3-N) decreased during the incubation period after applying NH4+-N fertilizer and urea. It maybe relates to the NH4+-N fixation, volatilization, and its nitrification.(4) Fertigation by drip irrigation increased the N uptake and accumulation of dry matter of summer maize, and improved the activity of crop photosynthesis. Root activity, NRA, and Pn/E were also increased by fertigation. When fertilizer was added as fertigation, the recovery of nitrogen fertilizer was high as 73.55%, with the 110.44% of increasing rate compared to traditional fertilization way; and corresponding increasing rate in dry weight of shoot and grain yield and water use efficiency were 49.55%, 67.57%, 109.20%, respectively. Obvi...
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