Study On Wheat Regulated Deficit Irrigation And Crop Evapotranspiration

Crop Regulated Deficit Irrigation(RDI) is one of water saving irrigation technology which base on crop's physiological and biochemical reflection to water deficit.RDI can increase crop yield, and decrease water consumption, and raise the WUE. RDI have great future in the arid semiarid area. If RDI was widely used in China, great economic and social Winter wheat and spring wheat are the material of RDI experiments in this dissertation. Energy balance and partition in the winter wheat field and wheat crop evapotranspiration are analysed based on the Bowen Ratio-Energy Balance Method (BREB).Straw-mulching which can work together with RDI is also discussed .The main results as follows: (1)After water deficit in wheat booting and maturity period, treatments have big difference each other on soil water, crop yield and photosynthesis rate (Pn). The more the field is irrigated, the more water consumption is. When stomata movement reach to an level, Pn will not increase obviously with it, but transpiration rate have positive liner correlation with it. There is hyperbola correlation between yield of winter wheat and irrigation water. The treatment which is irrigated 75mm water both in winter and booting period get the maximum yield, and minimum yield is taken by treatment .never irrigated. Water use efficiency (WUE) decreases when irrigated water increase. In common rainfall year (total rainfall 121.9mm in the whole winter wheat growth stage), if irrigated 75mm water both in winter and booting period, ideal yield and WUE could be gotten. (2)Based on the data getting from field experiment on spring wheat in 2004, this paper analyses the growth of plants and root, yield and its composition, water consumption and water use efficiency under different quantity of irrigation water and irrigation time. Result show that growth of plants is limited ,and growth of root is enhanced, and water consumption is reduced, and water use efficiency increase apparently, yield has little reduce when reducing irrigation water and detaining irrigation time properly. (3)Based on the BREB, energy partitioning in winter wheat field is explored. Each part of bowen ratio is sensitive to weather factor. Evapertranspiration coming form BREB also is compared with the data measured by Lysimeter. Trend of Latent heat changing is along with the net radiation, but daily change of sensible heat reverses with net radiation. Change of soil heat flux near the surface of field follow with net radiation after the jointing stage of wheat. Latent heat is higher than net radiation in winter, and it is 98% of net radiation after spring. Bowen ratio show irregular in the whole stage. Albedo go down wth leaf area index(LAI) increasing. When LAI surpass 1.7, evapertranspiration of BREB is similar with the Lysimeter. (4)Based on the field experimental data from 2003 and 2004, this paper analysed the soil water content, soil evaporation, soil temperature, maize plant height, leaf area index and yield under various quantity of straw mulching(0,1030 ,2060,3100 and 4130 ㎏/hm2). Results showed that soil evaporation of the most one of straw-mulching treatments was 10% less than the unmulched. The more field was mulched, the less the water consumption was. The water consumption of the mulched treatments was variously from 3.8% to 13.5% less than the unmulched. Soil temperature of the mulched treatments were all generally higher than the unmulched,especially in the upper 0～10 cm soil. With the increasing of quantity of straw mulching,temperature of the mulched treatments was higher variously from 0.2 ℃to 1.5 ℃than　the　unmulched　in　the　upper　layer.　In　each　growth　stage,　maize　leaf area index and height of the mulched treatments was higher than the unmulched., but difference among the treatments was not very clear. The more the field was mulched, the more the water use efficiency was, and the treatment of the most quantity of mulching was the best one on yield and water use efficiency.