| The fertility,structural and stability of farmland soil in the Loess Plateau area are poor Thus,the crop production in this area is heavily deepened on the application of chemical fertilizer.The unreasonable application of chemical fertilizer often exacerbates soil degradation.Biological soil crusts,which can fix carbon and nitrogen and improve soil fertility are widely distributed in the Loess Plateau region.As a green and sustainable biological measure,artificial algae crusts provide a new idea for soil erosion prevention and control and quality improvement of farmland on the Loess Plateau.However,at present,there are few studies to explore the impact of artificial algae crusts on the soil quality of farmland.Whether biological soil crusts can be formed in a short time after inoculation on farmland soil with better water conditions than desert soil.It is not clear whether the biological soil crusts affect soil nutrients,enzyme activity and crop growth.To this end,with respect to the above problems,this study took blank treatment as a control,and set up conventional chemical fertilizer,commercial algae fertilizer and artificial algae crust treatment.Using greenhouse pot and field plot experiment to study the impact of artificial algae crust on farmland soil nutrient content,soil enzyme activity and crop growth and development,as well as differences in chemical fertilizer and commercial algae fertilizer.On this basis,taking the four dominant native cyanobacteria species in the region as the objects,the greenhouse liquid culture test was used to study the appropriate culture temperature and initial pH conditions of different native algae species,in order to provide technical support for the use of artificial algae crust to improve the soil quality of farmland,and improve soil fertility and reduce the soil fertility of farmland in the region.Fertilizer application and consumption to reduce environmental pollution provide a new treatment idea.The main conclusions of the study are as follows:（1）Inoculation of cyanobacteria can significantly improved the rapid development of artificial cyanobacteria crusts.Under laboratory culture conditions for 50 days,the thickness of cyanobacteria crusts,biomass,and cyanobacteria crusts coverage were about2.43 mm,9.95μg·g-1,and 77%,respectively.In the field conditions of wind-water erosion interlacing zone on the Loess Plateau,the thickness,biomass,and coverage of cyanobacteria crusts were about 3.04 mm,3.71μg·g-1,and 88%,respectively,after 50 days.（2）The artificial cyanobacteria crusts formed 50 days after inoculation significantly increased soil nutrients.The increasing degree was related to nutrient species,soil depth and crust development.In terms of nutrient types,the increase effect on organic matter,total nitrogen and available nitrogen was significant.Compared to the control,in addition to increasing the content of organic matter,total nitrogen,and available nitrogen,artificial cyanobacteria crusts also significantly increased the content of total phosphorus and available phosphorus Specifically,organic matter,total nitrogen,and available nitrogen were increased by23.7-28.2%,22.5-26.4%,and 106%.Compared to chemical fertilizer,artificial cyanobacteria crusts significantly reduced the content of ammonium nitrogen and available phosphorus.However,the content of organic matter and total nitrogen increased by 7.93%and 27.7%,respectively,in the greenhouse.Compared to algal fertilizer,artificial cyanobacteria crusts significantly increased the nitrate nitrogen content and significantly reduced the available phosphorus content.The total nitrogen content only showed a significant increase in greenhouse conditions.In terms of soil depth,the influence degree decreases with increasing soil depth.Compared to the control,under greenhouse culture conditions,,the artificial cyanobacteria crusts significantly promoted the contents of organic matter,nitrate nitrogen,total nitrogen,ammonium nitrogen,and total phosphorus in the 0-2 cm soil layer.In the 2-5 cm soil layer,the contents of total nitrogen and nitrate nitrogen were increased significantly,1.23 and 11.0times higher than the blank soil layer,respectively.In the 5-10 cm soil layer,the contents of organic matter and nitrate nitrogen were significantly increased,1.21 and 12.22 times higher than the blank soil layer,respectively.Field conditions showed a significant increase in organic matter,nitrate nitrogen,and total nitrogen in the 0-2 cm layer,but no significant effect was observed in the 2-10 cm layer.Compared to chemical fertilizer,the artificial cyanobacteria crusts significantly increased the nitrate nitrogen content under greenhouse conditions,but decreased the ammonium nitrogen and available phosphorus content by20.8%and 72.8%,respectively,in the 0-2 cm layer.Increasing nitrate nitrogen in the 2-5 cm soil layer significantly reduced available phosphorus content by 67.7%.At 5-10 cm,organic matter increased by 7.9%,total nitrogen by 27.7%,nitrate nitrogen by 11.8 times compared to the blank,and available phosphorus content decreased by 55.6%.The content of available phosphorus in the 0-5 cm field was significantly lower than that of chemical fertilizer,but there was no significant difference between other nutrients and chemical fertilizer.Compared with commercial algae fertilizer,the algal crust significantly increased the nitrate nitrogen content in the 0-5 cm layer in both greenhouse and outdoor conditions.The content of total nitrogen in the 5-10 cm layer was increased by 13.8%,while the content of available phosphorus in the 0-2 cm field was decreased by 15.9%.In terms of crust development,the effects of artificial cyanobacteria crusts on soil nutrient content vary at different developmental stages.Generally,artificial cyanobacteria crusts can increase soil organic matter and nitrate nitrogen content,while decreasing ammonium nitrogen and available phosphorus content.These effects become more pronounced with increasing degrees of development.（3）Artificial cyanobacteria crusts has a positive impact on soil enzyme activity,which is dependent on enzyme type.Compared to the control,the activities of sucrase,alkaline phosphatase,urease,and catalase increased by 29.7%-113%,29.4%-46.4%,53.8%,and 21.4%,respectively.When compared to chemical fertilizers,the activity of most enzymes,except urease,increased significantly.Additionally,when compared to commercial algal fertilizer,alkaline phosphatase activity increased significantly,while sucrase and urease only showed significant increases in laboratory conditions,and catalase increased significantly only in the field.（4）Artificial cyanobacteria crusts can significantly enhance crop growth and increase the content of nitrogen,phosphorus,and potassium in comparison to the control.Regarding crop growth,artificial cyanobacteria crusts can significantly improve crop growth potential,biomass,and chlorophyll content in comparison to the control,and it can also promote root development with biomass increased by 115%-1820%.Plant height and root diameter were not significantly different from chemical fertilizer under greenhouse conditions,but leaf chlorophyll content was significantly increased.Under field conditions,growth potential,biomass,chlorophyll content,and root indexes were not significantly different from chemical fertilizer.When compared to commercial algae fertilizer,algal crust can significantly improve crop growth potential,biomass,chlorophyll,and root development,both greenhouses and outdoors.Regarding crop nutrients,the total nitrogen content and total phosphorus content of plants were increased by 4.5%and 21.3%under greenhouse conditions compared to the control,but the difference was not significant.The contents of total phosphorus and total potassium were increased by 47.6%and 43.4%,respectively,while the content of total nitrogen increased by 5.8%,but the difference was not significant.When compared to chemical fertilizer,the contents of total nitrogen and total potassium were increased by26.2%and 40.0%,respectively,under field conditions.（5）There was no significant difference in ecological adaptability among the four dominant local cyanobacteria tested,including Microcoleus vaginatus,Scytonema,Nostoc and Anabaena.At ambient temperatures of 25℃and 30℃,and an initial culture medium pH of 6,8,and 10,these cyanobacteria entered the growth stage rapidly and exhibited stable growth.A temperature of 35℃was conducive to the rapid completion of the cyanobacteria’s life cycle.The growth was slower when the initial pH of the culture medium was 4,which was beneficial for the accumulation of biomass.In conclusion,the inoculation of artificial cyanobacteria crusts in farmland in the Loess Plateau can rapidly form and improve soil nutrients,soil enzyme activities,and promote crop growth,yield,and nutrient content.The artificial inoculation of cyanobacteria crusts can serve as an environmental protection biological measure to control farmland soil in this area and promote sustainable agricultural development. |
PDF Full Text Request