| A fully balanced incubation trial designed as soil moisture×water-retainingAgent=3×4was conducted to reveal the effects of Water-retaining Agent on Nitrogenammonia volatilization under different soil moisture condition and a fully balancedfield trial designed as soil moisture×water-retaining Agent=4×2was conducted toreveal the effect of water-retaining Agent applied on yield and water utilizationefficiency of winter wheat in Sandy chao soil. We also study the effect of differentamounts of water-retaining agent applied with a20%nitrogen fertilizer cut-off onwheat yield and nitrogen utilization efficiency, with the control of no nitrogen appliedtreatment and normal nitrogen treatment. All about this study was trying to provideevidence for water-retaining agent induced the increase of water utilization efficiencyand yield in wheat. The main results were as follows:1. After32d’s incubation, the total ammonia volatilization curves were similar toeach other under three different Water-retaining Agent levels, which could describedby three types of dynamic equivalents: first order kinetics, Elovich equivalent andParabolic diffusion equation. The total ammonia volatilization under three moistureconditions that were treated by Water-retaining Agent increased with the extending ofincubation time, and they all showed W1>W2>W3.When the soil moisture were50%,75%and100%of field capacity and the Water-retaining Agent treatments wereB0,B1,B2and B3,the total ammonia volatilization was23.04,19.69,17.13,16.11mg,22.16,18.25,17.59,15.91mg and19.74,17.12,15.97,15.48mg, respectively. Thedecrease effect of Water-retaining Agent on total ammonia volatilization wouldincrease with the increase of amount of Water-retaining Agent and soil water contentwithin certain amount, while the effect of Water-retaining Agent would be weaken byexceed Water-retaining Agent or soil moisture. The less ammonia volatilization in thesoil could be arrived when the Water-retaining Agent amounts were more and soilmoisture content increased. When Water-retaining Agent amounts were same,compared with without Water-retaining Agent application, the effects ofWater-retaining Agent reduced the total ammonia volatilization were better under thelow soil water content condition. Soil urease activity and pH were influenced by soilwater content condition and Water-retaining Agent levels. With the increase of soilwater content condition and Water-retaining Agent levels, soil urease activity and pHall showed the tend of depressed, and the result could explain the discipline that theammonia volatilization changed with the different soil water content condition andamount of water-regaining agent. 2. Significant interaction effect of soil water content and Water-retaining Agentapplication amount on wheat yield were observed. The result shows that under theincrease of irrigation levels rate from20%-80%, the yield increased significantlywithout Water-retaining Agent, while In the application of Water-retaining Agent,corresponding to reduce irrigation water yield can reach the highest. With the increaseof irrigation levels, Soil moisture content increased, and it increased significantly inthe application of Water-retaining Agent. Both low irrigation levels and highirrigation levels weakened the effect of increase in Water Production Efficiency,Irrigation Utilization Efficiency and Rainfall Utilization Efficiency significantly,which was caused by Water-retaining Agent. A close relationship between yieldincrease cause by irrigation and Water Production Efficiency, Irrigation UtilizationEfficiency and Rainfall Utilization Efficiency was easily seen in this study. Thehighest yield was achieved by60%of the field moisture capacity irrigation combinedwith the application of Water-retaining Agent under this annual rainfall and climateconditions.3. A significant yield decrease was observed in a20%nitrogen cut-off treatment,compared to the normal nitrogen applied treatment. While the yield would increase by8.66%,24.51%and27.07%under the same nitrogen fertilizer treatment when20kg/hm2～80kg/hm2water-regaining agent applied, and remarkably higher yieldthan normal nitrogen treatment could be achieved by50kg/hm2～80kg/hm2water-regaining agent applied. Significant lower rate of total ammonia volatilizationcould be reached with20%nitrogen cut-off. The rate of total ammonia volatilizationwould present a lower trend from0to13d, as the increasing amount ofwater-regaining agent applied. A30.58%～40.55%lower lower total ammoniavolatilization could be seen in the20kg/hm2～80kg/hm2water-regaining agenttreatment when compared to the normal nitrogen treatment,0%～13.82%lower totalammonia volatilization amount could be seen under the same nitrogen treatment thanwithout water-retaining agent applied. Soil nitrate content in0-100cm in80kg/hm2water-regaining agent applied treatment increased significantly in wintering periodand seedling establishment period in the20%nitrogen cut-off treatment comparedwith no water-regaining agent applied. And as time went by, the soil nitrate contentwere remarkably higher in the water-regaining agent applied treatment than withoutafter elongation stage and the nitrate content would increase as the amount ofwater-regaining agent applied increase. The nitrogen accumulation of wheat in all ofthe growing period would decrease with a20%nitrogen cut-off treatment, but wouldincrease after elongation stage when20kg/hm2～80kg/hm2water-retaining agentapplied and would reach the same level as normal nitrogen fertilizer fortified when50kg/hm2～80kg/hm2water-retaining agent applied. Nitrogen use efficiency andpartial nitrogen productivity of applied would stay the same, but a significantdecreased agricultural efficiency could be observed with20%nitrogen cut-offcompared with the normal, while all of these three index would increase greatly in20kg/hm2～80kg/hm2water-retaining agent treatment and were higher than thenormal nitrogen applied treatment. |
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