| The karst areas in South China have abundant rainfall,developed river systems and densely distributed hydrographic net.However,due to the inherent land attributes and the geological conditions of the above ground and underground dual distribution in the karst rocky desertification areas,the underground leakage is serious,which leads to the fact that there is abundant water but lack of agricultural water.The problem of engineering water shortage is serious in karst area of South China."Opinions on further promoting sound and rapid economic development in Guizhou" issued by the State Council clearly points out that "there are bottleneck constraints in Guizhou's development,such as weak transportation infrastructure,serious engineering water shortage and fragile ecological environment...".The area of rocky desertification in Guizhou Province is the first in China,and the situation of rocky desertification is the most serious(Chen Qiwei,2013).The problem of rocky desertification and engineering water shortage seriously restrict the local economic development,seriously affect the relationship between man and land,and cause sharp contradiction between man and land.The water conservation capacity of mixed agriculture forestry project is strong,which is one of the good ways to repair the karst ecological environment and develop the local economy.In order to effectively develop mixed agriculture forestry under the condition of engineering water shortage,it is particularly important to develop the engineering water-saving,value-added and efficient production technology for mixed agriculture forestry under the rocky desertification environment.Based on the national "13th five year plan" key research and development projects,and with the theoretical coupling of geography,ecology,forestry science,soil and water conservation as the theoretical support,this study selected typical and representative "study area-Salaxi demonstration area with potential-middle rocky desertification of karst plateau-mountain in Bijie" ? "Guanling-Zhenfeng demonstration area with moderate-intensive rocky desertification of karst plateau-canyon in Huajiang",and "Shibing karst mountain potential light rocky desertification comprehensive control demonstration area" in karst area of South China.By means of data collection,field observation,comparative experiment and total factor analysis,8 representative mixed farming forestry modes were selected to carry out water-saving and value-added experiments.The experiment is the combination of water and fertilizer composite root irrigation technology and new water collection and film mulching technology.In 2017-2020,more than 1000 soil samples and plant samples and more than 4000 data of 16 indicators were tested and analyzed in 10 sample plots of three research areas by six consecutive field location observations and data collection.According to the response(and mechanism)of different mixed agricultural forest models and soil physical and chemical properties,the response(and mechanism)of new engineering water-saving and value-added technology to soil water,soil physical properties,soil nutrients and leaf transpiration in the mixed agricultural forest system are tested and studied,and the corresponding demonstration is carried out.The purpose of this study is to improve the existing micro drip irrigation technology,break through the limited technology research area,expand the extension scope of technology demonstration,and enhance the influence of its demonstration role by carrying out engineering water-saving and value-added technology experiments for different mixed agricultural forestry in karst area,so as to provide scientific reference for rocky desertification control.The main results are as follows:1.The difference of soil physical and chemical properties between the agroforestry model and crop monoculture model in karst rocky desertification is great,the absolute water content,capillary water capacity,field water capacity,total soil porosity and capillary porosity of agroforestry model are significantly increased(P < 0.05);compared with monoculture model,the soil pH of Ryegrass monoculture model in Bijie salaxi demonstration area is significantly higher than that of agroforestry model There was no significant difference in soil pH between the single cropping mode of prickly ash and the mixed farming and forestry mode in the demonstration area of GuanLing-Zhenfeng-Huajiang.The pH of the single cropping mode of pseudoginseng in Shibing demonstration area was significantly lower than that of the mixed farming and forestry mode.The prickly pear + ryegrass mode of salaxi demonstration area and the prickly ash + pomegranate mode of Huajiang demonstration area had the best soil nutrient content compared with other modes in the same demonstration area.2.The engineering water-saving,value-added and high-efficiency industrial technology significantly improved the soil nutrient content of agroforestry,and the impact on the physical properties of soil was related to the climate,soil quality and agroforestry model of the demonstration area,In the three demonstration areas,the soil bulk density of each model experimental group with engineering water-saving and value-added measures decreased,but only the difference of soil bulk density in Shibing demonstration area was significant(P < 0.05);in the three demonstration areas,the total soil porosity,field water capacity,capillary water capacity,saturated water content and capillary porosity all increased.Compared with that before the experiment,the pH value of the experimental groups in the three demonstration areas was significantly lower,and the content of nitrogen and phosphorus were significantly higher than that of the control group(P < 0.05).3.Compared with traditional irrigation methods,engineering watersaving and value-added high-efficiency industrial technology can effectively inhibit the ineffective evaporation of soil water,thus reducing irrigation water and improving water use efficiency.The ineffective soil evaporation of agroforestry decreased significantly(P < 0.05),The decreasing range of evaporation rate in different study areas is as follows: Shibing potential light Rocky Desertification Area > Bijie potential light Rocky Desertification Area > Huajiang middle strong rocky desertification area.In Shibing study area,osmanthus + pseudoginseng(48.21%),walnut + pseudoginseng(33.44%);in Huajiang study area,Zanthoxylum + pitaya(12.3%),Zanthoxylum + Broussonetia(22.49%),Zanthoxylum + pomegranate(25.82%),Zanthoxylum + walnut(23.4%);in Bijie study area,walnut + ryegrass(4.32%),Rosa + ryegrass(11.57%).4.Compared with the traditional irrigation method,the engineering water-saving and value-added high-efficiency industrial technology has significantly improved the transpiration and growth rate of plants;during the experiment,the overall trend of the increase of leaf weight is increased with the increase of total transpiration,the maximum increase rate of leaf weight is 236.81%(Rosa roxburghii Tratt,experimental group),the minimum is 2.64%(pitaya,control group).The average daily transpiration,total transpiration and water use efficiency of all plants were significantly higher than those of the control group.5.Based on the existing technology of water-saving and value-added of karst rocky desertification project and the unique agroforestry mode,and based on the climatic conditions of rocky desertification area in South China and the natural environment and social and economic conditions of different grades of rocky desertification,this paper puts forward the research and development of new key technologies,such as root irrigation micro drip irrigation,film mulching water micro irrigation,film mulching water and fertilizer conservation,to integrate the high-efficiency agroforestry for karst rocky desertification Engineering water-saving value-added industrial technology system.The results of the experiment and demonstration show that the water fertilizer compound root irrigation and the new water collection and film mulching water-saving and value-added technology can effectively improve the soil water use efficiency of agroforestry,have a good effect of soil moisture and fertilizer conservation,and have a good promotion prospect in karst areas.The results of the experiment and demonstration show that the water fertilizer compound root irrigation and the new water collection and film mulching water-saving and value-added technology can effectively improve the soil water use efficiency of agroforestry,have a good effect of soil moisture and fertilizer conservation,and have a good promotion prospect in karst areas. |
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