| During the period from the“Eleventh Five-Year Plan”to the“Thirteenth Five-Year Plan”period,the state invested special funds to carry out the control of rocky desertification,and explored the ecological industry technology suitable for the rocky desertification environment.The Fifth Plenary Session of the 19th Central Committee of the Communist Party of China required scientific promotion of comprehensive control of rocky desertification.According to market needs and local conditions,the promotion and planting of the Pyrus pyrifolia Nakai pear-based economic fruit forest at the Shibing Karst World Natural Heritage Site exactly meets the demand for comprehensive control of rocky desertification.The improvement of fruit quality based on the theory of water and fertilizer coupling can provide scientific basis for the theoretical research of related ecological industries.The efficient use of water and fertilizer is an effective means of soil and water conservation and ecological environment safety in heritage sites,and can effectively increase the ecological,economic and social benefits of rocky desertification areas.According to the theories of geography,botany,pedology,the balance of man land relationship and economic development,the mechanism of plant water regulation and environmental adaptation,the coupling of water and fertilizer and the function of ecological environment,aiming at the scientific and technological issues of how to improve the soil environment,improve fruit quality,determine the amount of irrigation water and fertilization methods,and integrate water and fertilizer integration technology.Shibing baiduo dolomite karst and Shiqiao limestone karst are selected as the study areas in Guizhou karst area,which represents the overall structure of the ecological environment of the Karst World Heritage in South China.From2018 to 2021,60 experimental plots in the study area were continuously monitored for soil moisture,plant moisture and soil and water sampling test.The methods of variance analysis,TOPSIS comprehensive evaluation and principal component analysis were used to clarify the effect mechanism of water and fertilizer coupling of different lithology on soil factors and plant growth and development,and reveal the mechanism of water and fertilizer efficient utilization and yield and quality improvement.Based on the comprehensive analysis and evaluation of soil nutrient quality and fruit yield and quality,the water fertilizer coupling quality improvement technology suitable for different lithology karst areas was proposed,and the integrated quality improvement control technology was demonstrated and verified,so as to realize the precision irrigation of Pyrus pyrifolia Nakai and provide guidance for the sustainable management of national and local rocky desertification control.（1）The soil nutrient content under mild deficit irrigation was higher than that under no irrigation and full irrigation.Compared with the control group and compound fertilizer mode,bio-organic fertilizer and earthworm manure fertilization mode could increase the soil nutrient content better:under W2F3（mild deficit+bio-organic fertilizer）mode,the soil available phosphorus（AP）,total potassium（TK）,calcium（CA）,sodium（NA）and total phosphorus（TP）content reached the highest.In W2F4（full irrigation+bean cake powder）mode,the content of soil organic carbon（SOC）was higher.In the other study area,under W2F1（deficit irrigation+earthworm manure）treatment,the contents of soil total nutrients and available nutrients reached the highest value.The contents of available K,available P and total P increased significantly after fertilization in Baiduo study area,and the average increase of soil trace elements Ca,Mg and Na was 22.46%;After the coupling of water and fertilizer,the increase of soil total nutrients was 10.42%higher than that of soil available nutrients,and the increase of Ca content in soil trace elements was the largest,with an increase of29.04%.（2）Reasonable water and fertilizer allocation increased the growth of dry weeks,new shoots,branches and flower buds,which indicated that water and fertilizer coupling had a positive effect on the growth and development of Pyrus pyrifolia Nakai pear.The growth of Pyrus pyrifolia Nakai pear in Baiduo（dolomite）area was more easily restricted by N element,and the growth of pear in Shiqiao（limestone）area was more restricted by P.W2F1（light deficit+earthworm dung）treatment in Baiduo research area had the most obvious growth of dry weeks and middle branches,W1F3 treatment（no irrigation+bio-organic fertilizer）increased the number of flower buds most significantly,while W2F3 treatment（light deficit+bio-organic fertilizer）increased the number of new shoots,long branches and short branches most significantly.In Shiqiao study area,W1F1 treatment（no irrigation+vermicompost）had the most obvious effect on the growth of dry weeks,while W3F1 treatment（full irrigation+vermicompost）had the most obvious effect on the number of flower buds,new shoots,long branches,middle branches and short branches.The leaf N:P（14.3）of Baiduo（dolomite）research area is equivalent to that of the national plant leaf scale（14.4）,which is consistent with that of other karst secondary forests（14.3）,indicating that the growth of pear in dolomite karst area is more easily restricted by N.The leaf N:P（20.76）>16,which indicated that the growth of pear was more restricted by P in Shiqiao（limestone）area.In the future,precise formula fertilization should be implemented to avoid the waste of nutrient elements and regulate the soil environment.（3）Reasonable water and fertilizer ratio has the ecological and economic benefits of improving soil nutrient quality and fruit quality.W2F3 treatment is the best water and fertilizer ratio in Baiduo area,while the the best water and fertilizer ratio in Shiqiao study area is W2F1treatment.Under W2F3 treatment,the comprehensive score of soil quality（3.67）and comprehensive evaluation score of fruit quality（0.76）in Baiduo area reach the maximum.It is the optimal water and fertilizer allocation mode.Under W2F1 treatment,the soil quality comprehensive score（3.35）and fruit quality comprehensive evaluation score（0.85）reached the maximum in Shiqiao area,which was the optimal water and fertilizer allocation mode.Under the W2F3 water and fertilizer ratio,the fruit yield of pear increased by 2741.04 kg·hm-2,the fruit moisture content,vitamin C content,reducing sugar content,soluble solid content and glucose content increased by 4.17%,1.91%,0.74%,2.75%and 5.14%,respectively,and the titratable acid content decreased by 0.05%.Under the W2F1 water fertilizer ratio,the fruit yield of pear increased by 2646.55 kg·hm-2,the fruit moisture content,vitamin C content,reducing sugar content,soluble solid content and glucose content increased by 11.09%,1.69%,1.28%,5.02%and 9.28%,respectively,and the titratable acid content decreased by 0.11%.（4）The difference in irrigation threshold is related to lithology.The irrigation threshold of in dolomite karst area isψsoil=-2.13 MPa,while the irrigation threshold in limestone karst area isψsoil=-1.72 MPa:the difference of irrigation threshold of soil water potential is related to the occurrence of water.The exposed water source in dolomite area is more abundant,and Shiqiao limestone area is more vulnerable to drought stress than Baiduo dolomite area.There is no linear correlation between soil water content and soil water content.Soil water potential does not increase infinitely with the increase of soil volume water content.When soil volume water content is greater than a certain value,soil water potential tends to be stable and soil water availability is the highest.The valley values of 0-15 cm and 15-30 cm soil water potential in Baiduo were-2.13 MPa and-0.63 MPa,respectively.The variation range of soil volume water content in Shiqiao is 0.16～0.44,and there are two fluctuating valley values of soil water potential.The valley values of soil water potential in 0～15 cm is-1.46 MPa and-1.19 MPa respectively,and the valley values of soil water potential in 15～30 cm are-1.72 MPa and-0.83 MPa respectively.To determine the critical soil water potential threshold in the life process of pear can lay a foundation for the realization of precision irrigation system in production practice.（5）Based on the theoretical research and the existing irrigation and fertilization technology of pear in the study area,the key innovative technologies such as soil improvement technology,plant water monitoring technology,cost saving and high efficiency technology were developed,and the key innovative technologies were demonstrated and verified.The demonstration effect was obvious:after soil improvement,the soil bulk density decreased and the soil quality improved.After applying bio-fertilizer,the content of soil organic carbon,available nitrogen,available phosphorus,available potassium and other main soil nutrients increased significantly.After application demonstration,fruit yield,fruit moisture content,vitamin C content,reducing sugar content,soluble solid content and glucose content were increased,titratable acid content was decreased,and core quality index of pear was significantly improved.After evaluating the economic and ecological benefits of the demonstration,the accumulated cost of the demonstration is 200000～300000 yuan·hm-2.From October 18 to November 2020,the demonstration sites are set up in the demonstration area,and the demonstration area is up to 20 hm2.In the process of ecological restoration of rocky desertification in the future,we need to tap the added value of ecological products,enhance the value space of ecological industry,and organically combine the work of"rocky desertification governance+targeted poverty alleviation+rural Revitalization". |
