| In recent years,60%of plants in the pasturing areas with water-saving irrigation in Inner Mongolia is grass,the highest percentage is alfalfa;In the process of promoting water-saving irrigation and forage grass land construction,drip irrigation has become the priority choice of the method of irrigation in the Midwest and water-shorted region.In this paper,based on the soil water infiltration test,field experiment and model simulation to research the key technical parameters and optimize the irrigation program with the subsurface drip irrigation,the main results are as follows:(1)Measure soil characteristic parameters and simulate the infiltration under the condition of the underground drip irrigation in sandy soil,it indicates that the sandy soil wetting front in the horizontal direction and downward motion with the subsurface drip irrigation is the same with ground drip irrigation.But the upward wetting front passage rate is smaller.When drip irrigation belt is buried deeply 15 cm,5 cm in soil moisture equals field capacity.Other points is up to the saturated moisture content merely,the irrigation uniformity with belt in 15cm is better than other points,it is the better choice.(2)Study impact factor on the key technical parameters with underground drip irrigation.Analyze the influence of drip irrigation flow,buried depth,irrigation quota on the height,root system,yield and drop head congestion,concluding that the depth has influence in the development of branch root,has little influence on the main root,non-significant on the height and yield.Due to the main root ranges from 10 to 30cm,proposing to bury at the 20cm.It meets the use of water as well as reduces the evaporation;When flow rate remains 2.0 L/h is good for the growth of alfalfa and has lower drop head plugging rate.(3)Based on water balance equation,calculate the water consumption and water consumption intensity of alfalfa in the whole period with the underground drip irrigation.Based on the calculation,the largest water consumption is at the second crop,ranges 172.64?189.10 mm;Higher than the other two crops,and the average is ranging 3.84-4.17 mm/d.The whole period water consumption ranges 406.00?478.47 mm,the water consumption intensity ranges 2.65?3.13 mm/d.(4)Calculate ETO according to Penman Monteith,modify the Kc with the method of double crop coefficient,and calculate the demand of water requirement of the whole period is about 450 mm with drip irrigation.the second crop water requirement is the largest,close to 200 mm.Compared the calculation of all three crops of water demand with the measured values,found that the relative deviation is 3.17%,2.1%and 4.6%.The calculated value and the measured values are close at the beginning of the alfalfa growth and apparent,indicates that the double crop coefficient method can describe the demand of water requirement very well.(5)Simulate the influence to yield on different irrigation schemes on alfalfa by DSSAT4.5 model,considering kinds of facts to gain the optimal irrigation program.On the high yield,irrigate about 35.0mm in each of the stubble alfalfa growth stage,irrigate four times,140 mm per crop irrigation,420 mm for the whole stages can guarantee the production of alfalfa.On water saving,optimization of W3,irrigate 15 mm in the period of seedling establishment,25 mm in other stages,4 times in the first two crops,irrigate 0 mm in the third crop,total 245 mm.On the least irrigation times,options W9,irrigate 2 times in the period of seedling establishment and the period of branch,irrigation quota is 35 mm,70 mm per crop,total 210 mm of the whole peiod. |
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