| Desertification is not only the ecological environment problems,but also the important economic and social problems.Worldwide,many countries are disturbed by desertification problem,More than 100 countries are influenced,and about 1 billion people are directly threatened by desertification.In global,desertification areas reach 36 million km2.In response to the problem,many techniques and methods have been put forward in the world.Engineering,chemical and biological methods are transformed into combined methods.Request changed from fixeing desert to improving desert ecological environment.This paper is based on:?1?Desert microalgae crust can fix sand soil in some degree,biochar is used as fertilizer and water retaining material.Firstly,we should restore and expand Microcolus vaginatus.Secondly,based on physicochemical property analysis,we choose 400?,6 h chaff biochar and400?,6 h sawdust biochar as our experimental material.This study set up14 experiment treatments,2 duplicate samples.With 400g desert sand as the basis,14 treatments were respectively blank sample,only applied into the chaff biochar 3 samples?mass ratio of 2%,4%,8%?,only applied into the sawdust biochar 3 samples?mass ratio of 2%,4%,8%?,only applied into the sample content of chlorophyll-a was 20 mg/L,3 treatments of microalgae combined with chaff biochar?mass ratio 2%,4%,8%?and 3 treatments of microalgae combined with sawdust biochar?mass ratio 2%,4%,8%?.Then,we through that sand table simulation of microalgae combined biochar mixed in desert soil in laboratory culture with 90 d.At the end of culture,it is tested and analyzed that soil particle diameter range,water retention rate,effective P content,total N content,organic C content and pH of desert soil:?1?Biochar can effectively improve desert soil fertility.In 6 treatments treated with biochar alone,the content of effective P,total N and organic C in desert soil increased with the increase of biochar application.The best of which is applied into the 8%chaff biochar,soil effective P content was 4.6times higher than that of blank treatment,total N content was 2.1 times higher than that of blank treatment,and organic C content was 2.4 times higher.The nutrient content in soil increased significantly.?2?Excessive adding biochar can hinder the microalgae crust.After applying biochar with a mass ratio of 8%,the pH of desert soil increased,which caused that salinity-alkalinity stress of microalgae.The experiment showed that the growth rate of microalgae was inversely proportional to the quality of biochar.The right amount of biochar had no effect on the growth of microalgae crust.Adding 2%,and 4%of the chaff biochar and 2%sawdust biochar in desert soil,micro algae can still form a crust.Moreover,under the combined action of microalgae crusts and biochar,the pH of the tested soil dropped to the range of weak alkali-neutral.?3?Biochar has better water retention effect in sandy soil.Among them,microalgae combined with 8%chaff biochar had better water retention effect in desert soil,and the water retention has 68%after 10d,which was 21%higher than that of blank treatment.In 0 to 10 days,the water content in the sand decreased linearly with faster,and rate of slow descent after 10 days.?4?Microalgae combined with biochar improved desert soil better than single application of biochar.The combination of microalgae and biochar was the best.When 8%biochar was applied,the effective P content reached33.74mg·kg-1,which was 9%higher than biochar alone.The total N content of 2%chaff biochar was 3.43%,17 times higher than 2%chaff biochar alone.Therefore,from experimental results and economic costs,the combination of microalgae and 4%chaff biochar are best choice in sand fixation and desert soil improvement. |
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