| The imbalance between increasing population and increasing production of agricultural land area are considered as important problems of the world today.Supply of global food security is a basis for economic,political stability cultural and social evolution.Therefore,the food production must be increased to match future food demand.According to reports from the United Nations there will be a continued increase in the population in the future.However,cultivated land has become increasingly rare.Therefore,increasing the production of food can only be reached through condensation of high yield and quality of crops,so more intense crop production could lead to more utilization of organic and inorganic fertilizers.Sulfur plays an important role as a nutrient in plant growth regulation,metabolism,and plant quality,beside nitrogen,phosphorus and potassium.In addition,sulfur is essential for the soil stress resistance and detoxification.At present,sulfur deficiency in soils cause huge losses in agricultural production in about 70 countries and regions around the world.This potential sulfur deficiency affects the quality of agricultural products,and poses a potential threat to the ecological environment.Therefore,the study of sulfur content and its bioavailability in soil has received extensive attention.The biochar is a carbon-rich particle that is pyrolyzed by biomass?such as straw,animal manure,municipal sludge,etc.?under limited oxygen conditions.The biochar has a great potential for application in soil improvement,carbon reduction,soil pollution control,etc.It has become one of the research hotspots in the international soil and environmental community.Biochar has an advanced pore structure,large specific surface area,and has strong adsorption performance,so it can adsorb inorganic and organic nutrients in the soil.It also can effectively reduce the loss of nutrients in farmland soil,and increase crop yield.Furthermore,biochar has direct nutritional and indirect nutritional value,when biochar is applied to soil,it will not only affect the physical and chemical properties of the soil,but also will directly or indirectly affect the environmental chemical behavior and bioavailability of nutrients in the soil.Plants mainly absorb sulfur from the soil in form of sulfate anion through the rhizosphere.The absorption of sulfur by plants in the presence of biochar is related to the source and properties of biochar,soil properties,plant species,and soil environmental factors.Loess soil has the characteristics of loose structure,strong water permeability and poor agglomeration,which results in the easy leaching of nutrients in loess.Therefore,biochar should be applied in the loess in order to improve the structural as well as the physical and chemical properties of the soil.At the same time,it is expected to enhance the bioavailability of nutrient elements?sulfur?and ensure the quality of farm products.The changes of physicochemical properties of soil and bioaccumulative sulfur after biochar application to loess in the presence of biochar have yet to be studied.This research has briefly introduced the progress of biochar application technology in environment and agriculture field and the bioavailability of sulfur in the soil.It also reviewed the preparation of biochar and its impact on the plant growth.The mechanism and the effects of biochar after application on loess soil and the absorption of sulfur by plants are still not clear.This study selects maize straws and corn cobs as biomass raw materials and prepares biochars at different temperatures?BMS300,BMS600 and BCC300,BCC600 respectively?,through the elemental analysis,specific surface area,scanning electron microscopy?SEM?,Fourier transform infrared spectroscopy?FTIR?,X-ray diffraction analysis?XRD?and other means to characterize the surface properties and structure of the prepared biochar.In crop planting experiments,the effect of biochar application on the physicochemical properties of loess,plant growth and development and sulfur bioavailability was studied under five biochar treatment rates?0,7,14,21,28 gC/2 kg soil?.The research results can provide scientific basis for the application of regional soil biochar and the protection of agricultural product quality.The main results of this paper are as follows:?1?With the increase of the preparation temperature of biochar,the yield of BCC decreased from 48.89%to 26.55%,and the yield of BMS dropped from 35.97%to 19.65%.There is a large correlation between the ash content of biochar and the pyrolysis temperature,and the ash content of biochar increases with the increase of pyrolysis temperature.Under the same pyrolysis temperature conditions,the ash content of BMS is higher than that of BCC.With the increase of pyrolysis temperature,the pH value of biochar increased,from 8.63 in BCC300 to 11.03 in BCC600,from 9.42 in BMS300 to 11.42 in BMS600.The conductivity of biochar increases with temperature.Biomass sources and pyrolysis temperatures were diverse in the specific surface area of the prepared biochar.The specific surface area of the BMS prepared under the same conditions which is higher than that of the BCC.SEM spectra showed that the biochar prepared at high temperature obviously has more pore structure.The FTIR results,exhibited the surfaces of BMS300,BMS600 and BCC300 and BCC600 contains rich oxygen-containing functional groups?—OH,C=O,C=C,Si—O—Si,etc.?.XRD results showed that biochar was mainly composed of quartz and calcite.The analysis of the sulfur content of BMS300,BMS600 and BCC300 and BCC600 shows that as the pyrolysis temperature increases,the content of water-soluble sulfur gradually increases from 0.07%of BCC300 to 0.17%of BCC600 and 0.015 of BMS300 increases to 0.31%of BMS600.At the same time,the results of NaH2PO4-SO42-showed high level in all types of biochar.The sulfur content of HCl-SO42-was higher in BMS than BCC when the pyrolysis temperature was at600°C?2?The effects of BMS300,BMS600,BCC300 and BCC600 physicochemical properties on soil and maize growth were studied.The increase of biochar application showed an increase in soil pH compared with CK?B0?,and there was a significant difference among all treatments?P<0.05?.An exception,the increased application of BCC300,firstly showed an increased soil pH value which was then followed by subsequently decrease.The application of biochar treatment had no significant effect on soil EC compared with CK?B0?.Soil urease and catalase activity showed an increasing trend?P<0.05?by the increase of biochar application amount.?3?The results showed that the biochar derived from slow pyrolysis significantly increased the maize height,stem,number of leaves,fresh weight,dry weight,and chlorophyll content.The application of various rates of biochar has different impacts on the maize growth.The application of BMS600 can significantly increase the maize height,compared with CK?B0?in biochar rate B2,whereas,it decreased in B3 and B4.When the biochar application amount was applied in B2,the highest values?89.6,82,81.8,and 79.3 cm?of plant heights were recorded at BMS300,BMS600,BCC300,and BCC600,respectively.The effect of biochar application on the maize's diameter showed a significant increase in BCC300 and non-significant increase in BCC600 and BMS300,whereas the increase of the biochar application amount,the number leaves were increased.This may be due to the fact that excessive application of biochar will inhibit the growth of maize.The fresh weight and dry weight of maize increased significantly with the increase of biochar application amounts,and reached a significant level among different treatment groups?P<0.05?.Chlorophyll content of maize leaves increased gradually with the increase of biochar application amount,and reached a significant level among different treatment groups?P<0.05?.The results showed that the application of biochar can improve the photosynthesis ability of maize.In addition,the results indicated that the maize straw and corn cob biochar improved soil properties,nutrient retention,and plant growth.?4?The application of sulfur addition in the presence of biochar has an effect on the maize growth and the plant availability of sulfur in loess soil.Under low concentration of sulfur application,the maize diameter and number of leaves were increased significantly with the increase of the pyrolysis temperature of biochar?P<0.05?.When the biochar treatment was applied at B4 under all levels of sulfur application,the maize diameter and the number of leaves were decreased.Under the same application of sulfur concentration,the fresh and dry weight of maize increased with the increase of biochar application amount,and reached a significant level when the biochar was applied at B4?P<0.05?.The results showed that the application of sulfur in loess could significantly increase the biomass of maize growth,and the low concentration of sulfur application had a more significant promoting effect than the high concentration of sulfur.The chlorophyll content of maize increases at the same sulfur application with the increase of the biochar application amount,then decreases and reached a significant difference level?P<0.05?.The application of biochar can increase the sulfur absorption by maize,compared with CK?B0?.Under the low concentration of sulfur,the sulfur content of maize leaves and roots increased significantly with the increase of biochar application?P<0.05?.Currently,the use of biochar is not commonly applied in agronomy.Therefore,more investigation should be conducted to evaluate the effects of biochar on soil properties and plant growth.In conclusion,based on the results derived from this study,as well as previous studies,biochar should be considered as an alternative solution for various soil and environmental problems,also it has been demonstrated as an eco-friendly system. |
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