Study On Irrigation Indexes And Spatial Variability Of Soil Moisture And NO₃～--N Content In Wheat Field Under Sprinkling Irrigation Condition

In general ,the irrigation frequence or irrigation date of irrigation system was determined by the legal water management with the relationships among soil-water-plant and variation demanded by evaporation were neglected. It's very necessary to establish the relationships between soil water content, discrepancy between canopy and air, leaf water potential with the water status of plant. Based on the relationship a optimal irrigation time and irrigation norm can be made . The study on the spatial variability of soil moisture and N03^--N content under sprinkling irrigation conditions is important as well,the result shows some merit in increasing water use efficient and fertilizer use efficient and decreasing the waste of nitrogen and protecting the enviroment from being polluted.The field experiment were carried out in sprinkling area at Luancheng Agro-ecosystem Experiment Station (LAES) of Chinese Academy of Science during march,2002 to june,2002, by using the auto sprinkle irrigation system made by institue of soil science in nanjing. The experiments include two aspects: the study of the irrigation indexes under sprinkling irrigation condition, the study on the spatial variability of soil moisture and N03^--N content under sprinkling irrigation condition. By using the advanced equipment and facilities at LAES,many information and data were collected from those experiments.Those experiments were as following:based on the daily variation and the variation in the whole growing stage of winter wheat of soil moisture, soil evaporation under wheat canopy, leaf water potential, root distribution and canopy temperature, then a optimal irrigation system can be made with limited water amount. The relationship between relative yield and relative water use is formulated,based on these data, a optimal irrigation scheduling under sprinkling irrigation condition can be made or the lower level of soil moisture in different growing stage might be teken as the indicator for the scheduling irrifgation in winter wheat.Spatial variability of soil moisture and N03^--N content in a range of 0⁶0cm is studied with geostatistics and semi-variogram under different irrigation systems, Then the Semi-variance were matched with different kinds of model and the contours-N content and soil water content were generated by using the Kriging interpolation. The results can showed the sprinkler uniformity and soil characteristics and so on, it also showed some merits in increasing water use efficience and precision agriculture. The study on the spatial variability and the factors which caused the variabilty is important to learn the principle of water balance and increasing sampling efficiency.