Simulation Of Soil Nitrogen Balance And Development Of SISNDB Information System

Nitrogen is the important element for the beings, and the essential for the sustainable development of the agricutural production. Nitrogen fertilization takes a great contribution to crop production in recent centry. A large part of it lose to environment, by ammonia volatilization, denitrification, runoff and leaching, with low use efficiency of the nitrogen fertilizer, which greatly threatened the survival of the humankind. Soil nitrogen is very important for harmonizing the increase of crop yield and envrionmental protection. Based on the former achievements and the traditional means, the combination of the new methods are expected to be helpful for the better understanding of soil nitrogen balance, which will also do good to the advancement of research in sustainable development of the agricutural production, the rational, economical fertilization, and the preferable environmental protection.In view of the complexity and the comprehensiveness, mathematical modelling plays an important role on the anlysis of soil nitrogen balance and its impact on environment, which is a hot topic and a hard task. Until now, most of the models focus on soil nitrogen balance in the upland, but little has been done on wetland rice field, containing all the major processes of nitrogen cycle. Aimed at appling nitrogen fertilizer in reason and reduce its negative impact on environment, the mechanism of soil nitrogen balance in the soil-crop system is systematically studied in the case, based on the related internal and external research, and our experience. In detail, two main aspects are as follows:(1) Developing dynamic simulation model and information system for soil nitrogen balance. Based on the former achievements, and through the mechanismanalysis and validation experiment, the dynamic simulation model for the soil nitrogen balance, esp. for wetland rice field, is built and its information system is programmed. The simulation and information system consists of such submodels as soil nitrogen balance, soil water balance and crop growth. The criteria for the design of the system is easy to apply as well as powerful in analysis. This study is expected to supply a gap in this field in our country, and to be a useful tool to analyse the processes of soil nitrogen cycle and the loads to the environment. (2) Integration of ComGIS (Component GIS) and soil water balance and crop growth coupled model. It is required to be independent of general purpose GIS platform, and its parameter sets should be simplified to faciliate popularization. This study gives decision-making support for the agricultural water management, and lays the foundation of the integration of ComGIS and the simulation model for soil nitrogen balance.After years of hard work, the anticipated goals have been accomplished. Soil nitrogen balance dynamic simulation model and its information system have been established, and ComGIS-based simulation and information system for soil water balance and crop growth model has also been completed. Such innovated progress have been achieved as follows:(1) Referred to the fomer soil nitrogen models concerned, conforming to the powerness and practicability, SISNDB (Simulation and Information System for Soil Nitrogen Dynamic Balance) are developed. This system is designed user-friendly, easy to use, less parameter to input and powerful to simulate. It is the first one in our country, and makes a great step in this field in China.(2) This information system for soil nitrogen balance is special for paddy field, which takes the lead of this field in the whole world. The system is expected to be effective for management nitrogen fertilization and environmental protection.(3) Integration of ComGIS and soil water balance and crop growth coupled model SISWBCG (Simulation and Information System for Soil Water Balance and Crop Growth), has been accomplished, as a platform for integration of ComGIS and soil nitrogen balance dynamic simulation model. Being of our own intelligence property,the system can work free of GIS platform, and its interfaces are all designed in Chinese language. Minimum data set based on sensitivity analysis of parameters has been made, which greatly facilitates learning and using. SISWBCG system is expected to be a useful tool for agricultural water management. Additionally, it serves as a basis for the combination with RS and GPS in the future to conduct the precision irrigation and fertilization.In this study, sensitivity analysis and validation have been done, and simulation on different variety, timing, amount for fertilization and different water management have been made. Results are concluded as follows:(1) By the sensitivity analysis for parameters in SISNDB system, the results are satisfied. The minimum saturated hydraulic conductivity in the whole profile (for paddy soil, the saturated hydraulic conductivity in plough layer), the parameters for water management and weather (temperature, rainfall and wind speed) are all very sensitive to the processes of soil nitrogen balance. The results of validation experiment indicated that the simulated values agreed the observed quite well.(2) The simulation for urea and ammonium sulphate shows that the different fertilizers could change the processes of soil nitrogen balance. Compared to ammonium sulphate, urea application will produce less ammonia, but will increase denitrification loads. During one week after fertilizer application, NH4+-N is liable to loss in runoff if it rains; for NCV-N, nine to ten days are critical for runoff loss. Soil nitrogen loads by overflow from paddy field can be decreased if the time of fertilization keeps away from the rain. NH4+-N is more than NCV-N in leaching and runoff for two fertilizers.(3) From simulated results of the different fertilization pattern, it can be concluded that the timing of fertilization could change the processes of soil nitrogen balance, such as NHt+-N and NCV-N concentration in paddy field surface water and leaching water. Basal fertilization has the biggest impact. The next is top dressing at tillering stage and at blooming stage, and the minimum is top dressing at ear differentiation stage. The concentration and overabundance fertilization during the former phase of rice growth will definitely cause a great deal of soil nitrogen loads to water and...