Study On Climatic Potential Productivity And Irrigation Suggestion In Shiyang River Basin

Climatic potential productivity is the maximum biological production or agricultural production that the per unit area of land may be given when fully and rational use of local climatic resources such as solar radiation, heat and water, while other conditions (such as soil fertility, carbon dioxide concentration, cultivation level etc.) at the optimum situation.The estimate of climatic potential productivity will explore the crop potential productivity under a certain climate, soil and agricultural technology level condition and provides a scientific basis of estimating population carrying capacity of land,planning regional agricultural development, and rational utilization of climatic resources.Based on the "mechanism method" principle, according to photosynthesis, temperature, moisture"decay process", to estimate the photosynthetic potential productivity, light -temperature potential productivity and climatic potential productivity of spring wheat and maize in Shiyang River Basin respectively. Using GIS software to put the photosynthetic potential productivity, light-temperature potential productivity and climatic potential productivity of spring wheat and maize into property database to make the thematic maps of photosynthesis, light-temperature, climatic potential productivity spatial distribution map and analyze their spatial variation. According to the analysis of photosynthesis, ligh-temperature, climatic potential productivity in the Shiyang River Basin, to find the major constraint factors of spring wheat, maize potential productivity and propose corresponding countermeasures and suggestions. Then, based on the meteorological data in Shiyang River Basin, by using FAO's CROPWAT model to calculate the evapotranspiration and effective precipitation of spring wheat and maize, thus get the irrigation water requirements of spring wheat and mazie. Combination of GIS software, using ArcGIS and Arcview to analysis the spatial distribution of crop evapotranspiration, effective precipitation, irrigation water demand of spring wheat and mazie ,meanwhile ,provide reference for exploring the crop yield in Shiyang River Basin.This paper presents the following main conclusions:(1)The photosynthesis, light-temperature, climatic potential productivity of spring wheat were 15500.71~17186.60kg/hm2, 7643.59~10841.88kg/hm2 and 301.76~2863.29kg/hm2 respectively; while the three of maize were 22704.79~25732.44 kg/hm2,10665.73~17189.27 kg/hm2 and 360.97~3947.91kg/hm2 respectively.It can be seen that Shiyang River Basin had plentiful solar radiation resources,the major limiting factor of spring wheat and mazie production was the moisture factor. The spatial distribution tendency of photosynthesis, light-temperature potential productivity were decreased from north to south; the climatic potential productivity was increased from north to south in Shiyang River Basin which consistent with the spatial distribution of meteorological parameters that reflect the River Basin's photosynthesis, light-temperature, precipitation, potential productivity, such as sunshine hours, solar radiation, temperature, precipitation, etc.(2) Through the analysis of the interannual variability of Minqin and Gulang's climatic potential productivity ,it was showed that the interannual change of photosynthetic potential productivity of spring wheat were 15544.63~18142.72 kg/hm2 and 14470.26~16899.42 kg/hm2 , the relative variability were 3.67% and 3.33% in Minqin and Gulang respectively; the inter-annual change of light-temperature potential productivity of spring wheat were 9429.11~12234.60kg/hm2 and 5671.58~8257.28 kg/hm2, the relative variability were 5.38% and 8.71% in Minqin and Gulang respectively ;the climatic potential productivity of spring wheat were 119.64~529.53 kg/hm2 and 1744.08~3617.42 kg/hm2, the relative variability were 34.97% and 18.96% in Minqin and Gulang respectively.So the the interannual variability of precipitation is the main factor which influence the crop yield in Shiyang River Basin.(3) The average annual evapotranspiration of spring wheat was 353.55~452.60mm,the average annual precipitation during the spring wheat growth period was 46.77~174.26mm; the average annual evapotranspiration of maize was 463.73~561.75mm, the average annual precipitation during the maize growth period was 87.11~257.87mm in Shiyang River Basin. The proportion that the precipitation account for evapotranspiration of spring wheat and maize were 10.33~46.98% and 15.51~52.55% respectively, so the precipitation can not meet spring wheat and maize's evapotranspiration. Thus, only rely on precipitation, it will cause the production reduction of spring wheat and maize.In order to guarantee the production of spring wheat and maize, the spring and maize required complement irrigation. The results calculated by CROPWAT model showed that the average annual irrigation water requirement of spring wheat and maize were 202.79~407.47mm and 248.33~479.87mm respectively in Shiyang River Basin.(4) The photosynthetic resource utilization rate of spring wheat and maize were 18~40% in Shiyang River. The high value area locate in the north of Shiyang River Basin, followed by the middle of Shiyang River Basin, the photosynthetic resource utilization rate was 30% ;Low value area concentrated in the south of Shiyang River Basin. The light-temperature resource utilization rate varied with temperature resource conditions, So the photosynthetic resource utilization rate was slightly different with that light-temperature was . The light-temperature resource utilization rate was 50~70% in the north of Shiyang River Basin, however, the value was low which about 30~50% in the south of Shiyang River Basin. The photosynthetic potential productivity of spring wheat and maize were 3.06 and 3.01 times as the actual yield respectively;the Potential Index of spring wheat and maize were 40.16% and 41.84% respectively, it indicated that the the productivity potential was large in Shiyang River Basin .In order to maximize the climate resource utilization, some measures should be taken such as to improve irrigation conditions, soil nurture and to improve farm management and chemical fertilizers, pesticides and so on.(5) Based on the analysis of photosynthesis, light-temperature and climatic potential productivity in Shiyang River Basin, there are several countermeasures to imrpove climate resource utilization rade and increase reality crop yield. 1) to strengthen water conservancy protect construction ,guarantee the irrigation water supply during crop growth period ;2) to adopt and cultivate good crop species; 3) increase the potential productive of precipitation; 4)to make full use of land of natural resources and increase the multiple crop index;5)to develop facility agriculture.