| In order to alleviate the pressure of water supply and realize the sustainable development of irrigated agriculture,corn straw and soil were used as raw materials to produce straw composite pipe(SCP).The SCP is buried in the field for irrigation,which has the two major effects of water-saving irrigation and returning straw to the field,so as to realize the technical integration of "1+1>2".The SCP is the core of the straw underground irrigation technology,which is initially formed.Under the great pressure of the shortage of agricultural water supply and the integration of agricultural resources,the proposal of straw subsurface irrigation technology provides a new way of thinking for the rational utilization of water-saving irrigation technology and agricultural resources,which is of great significance to the sustainable development of green irrigation agriculture and agricultural resources.Based on the field application of straw composite pipe,the hydraulic performance and plugging mechanism of straw composite pipe were studied.According to the research on the hydraulic performance of straw composite pipe in the field,the preliminary test on the hydraulic performance of straw composite pipe with straw content and straw composite pipe length as experimental factors and the field test on the hydraulic performance of straw composite pipe with pipe length,pressure head and irrigation amount as experimental factors were carried out respectively;for the research on the degradation mechanism of the performance of straw composite pipe,the sampling investigation was carried out The degradation of straw composite pipe was studied qualitatively and quantitatively by the way of combining observation analysis and hydraulic performance test.The degradation mechanism of straw composite pipe was deeply analyzed.Through the analysis of the test results,the change rule of hydraulic performance of straw composite pipe under field irrigation and the degradation inducing mechanism of straw composite pipe were understood,which laid the foundation for the field application of straw underground irrigation technology.The results are as follows;(1)under the condition of different length and straw content test,with the increase of straw stalk length of pipe buried,unit length cumulative flow showed a trend of increase,irrigation uniformity decrease trend: straw content was 5%,7% and 9% levels,3.5 m per unit length of pipe of CSS cumulative flow more than 1.0 m,respectively,71.66%,77.52%,8.14%,irrigation uniformity decrease 3.60%,5.45% and 13.72%respectively.(2)With the increase of straw content,the cumulative discharge per unit length of straw composite pipe with different lengths showed a decreasing trend: under the condition of pipe length of 1.0m and 3.5m,the cumulative discharge per unit length of straw composite pipe with straw content of 7% and 9% decreased by 12.60%,15.80%,9.09% and 18.70%,respectively,compared with that with straw content of 5%.(3)The relationship between the infiltration rate and irrigation time of SCP conforms to the law of power function.Considering the discharge,infiltration rate,uniformity and other experimental indexes,it is considered that SCP has the conditions to be used as irrigation capillary for field irrigation.When the amount of straw is 5% ～7%,the hydraulic performance of SCP is the best Finally,when the straw content is 7%,the performance of straw composite pipe is the best.(4)Through the analysis of the results of the field irrigation experiment on the SCP with the buried length of 80 m.The function fitting of the relationship between the infiltration rate and time showed that there was a good power function relationship between the instantaneous infiltration rate and irrigation time,which was consistent with the previous experimental results,and proved the technical feasibility of SCP field application.(5)In the field irrigation experiment,it was found that under different irrigation amount,24 hours after the end of the irrigation experiment,the surface wetted body of this section was still in point or block shape,and the irrigation uniformity decreased after 40 ～ 50 m from the pipe head.It was speculated that the suitable laying length of SCP in the field was about 40 ～ 50 m.SCP underground irrigation technology should be a water-saving irrigation method based on low pressure,buried length,small amount and high frequency.(6)The degradation mechanism of the composite tube was investigated and studied.The degradation of the composite tube was caused by many factors.It was marked that the function of SCP declined and then the straw composite tube was blocked.The influencing factors of the tube degradation were physical cause,biological cause and external cause.(7)The distribution of bulk density in the degradation process of SCP is similar to normal distribution,which objectively reflects two degradation trends of SCP under different natural conditions.The results show that the times of water supply can reduce or alleviate the degradation trend of hydraulic performance of SCP to a certain extent,and the performance degradation of SCP is a reciprocating process.(8)The relationship between water storage rate and water discharge time per unit length of SCP is a power function.The degradation of hydraulic performance of SCP can be evaluated by the water discharge time per unit length of SCP.Straw underground irrigation technology with SCP as the core is a new field in scientific research.It organically combines the existing water-saving irrigation technology and straw returning technology,which is conducive to promoting the sustainable development of national agriculture and the healthy development of farmland irrigation,and stabilizing the national food security.This conclusion of straw application and straw in the field of the multiple tube and underground irrigation technology promotion has certain reference value,but the straw underground irrigation technology is still in its infancy,the establishment of the relevant theoretical system is not perfect enough,there are still many areas need to experiment to explore,related research remains to be further in-depth and detailed. |
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