Determination of crop evapotranspiration and crop water requirement calculation method |
|
Author | FanYinQin |
Tutor | CaiHuanJie |
School | Northwest University of Science and Technology |
Course | Agricultural Soil and Water Engineering |
Keywords | Evaporation Evapotranspiration Lysimeter Crop water requirement Crop coefficient |
CLC | S311 |
Type | Master's thesis |
Year | 2001 |
Downloads | 1335 |
Quotes | 33 |
Farmland Evapotranspiration is not only an important part of the water balance study, and the development of irrigation schemes, as well as evaluating the climate resources and water supply situation, there is an important role in agricultural production. Accurate determination of soil evaporation on the soil surface to reduce invalid evaporation, improve water use efficiency is important. In this paper, a combination of large-scale Lysimeter and Micro-Lysimeter study the process of change and influencing factors of winter wheat and summer maize daily evapotranspiration and evaporation; analysis of the evaporation of the proportion of total evapotranspiration with leaf area index and surface changes in soil moisture relationship, after irrigation, soil evaporation process of change; measured evapotranspiration, evaporation diurnal variation, the variation coefficient of evaporation and transpiration sharing and meteorological factors on the daily evaporation transpiration; using two different materials , the different specifications micro Lysimeter respectively measured soil evaporation, and analysis of the differences and the reasons. Single crop coefficient approach and dual crop coefficient approach FA0-56 recommended winter wheat and summer corn crop water requirements were calculated and compared with lysimeter measured, differences and reasons. Showed that the evapotranspiration of winter wheat water consumption peak after reviving, especially heading - Grouting period; the soil evaporation water main in the winter before. The summer corn evaporation Transpiration peak after jointing. The soil evaporation mainly by the impact of surface soil moisture, evapotranspiration dramatic change with the crop's development process. Leaf area index and surface soil moisture are the two basic factors to control evaporation. E / ET with the increase in leaf area index decreased; effective coverage on the ground (of LAI> 3), the E / ET with the increase in the surface soil moisture increases. Ground cover in the early stages of crop growth, crop evapotranspiration, soil evaporation between the main, E accounted ET proportion great; with the development of the crop canopy, the increase in the degree of ground cover, mainly to transpiration, soil evaporation proportion gradually decreases. Evapotranspiration, solar radiation is the main influencing factors. Lysimeter determination of evaporation is a simple, effective and feasible method, but different material specifications micro Lysimeter measured evaporation value of the same. Lysimeter back cover of the same material, the same specifications or not have a certain influence on the measured values, while the placement has no effect on the measured evaporation. Ground partially covered the case, the calculated value of the dual crop coefficient approach than the calculated value of the single crop coefficient approach closer lysimeter measured values; two methods calculated value is very close to the ground is completely covered. Overall, the results of the two methods of calculation have a good correlation. Single crop coefficient approach is simpler than the dual crop coefficient approach, proposed during the growth period of the crop water requirement calculated using single crop coefficient approach; However, the use of crop water demand for irrigation forecasting and irrigation decisions required period of hours, using the dual crop coefficient approach .