The Properties Of Biochar Derived From Crop Residues And Its Using Effects In Albic And Black Soil

Biochar, a by-product of biomass pyrolysis under the condition of anaerobic andhypoxia, has stable structure and carbon sequestration and can exist more thanhundreds of years or even thousands of years in soil. The beneficial effects of addingbiochar to soil include improved soil fertility, soil moisture retention and promotedplant growth. These beneficial effects are extremely promising and could have aprofound positive influence on environment protection, food and energy crisis, whichcaused biochar become a hot research topic these years. This study focused on thebasic characteristics of biochar derived from crop residues and their improvementeffects on the quality of soil.We studied the yield, pH, carbon and nitrogen contents of three kinds of biocharswhich were derived from corn cob, soybean stalk and rice husk by the muffle furnaceat different pyrolysis temperature (300°C,400°C,450°C,500°C and550°C) for3,6and9hours, respectively. The results showed that the yield of biochars decreased butthe pH increased with the increasing pyrolysis temperature and duration time. Thecontent of biochar-carbon derived from corn cob and soybean stalk increased with theincreasing pyrolysis temperature and duration time. However, for the biochar derivedfrom rice husk, the biochar-carbon content did not change remarkably. The nitrogencontent of biochar derived from corn cob and rice husk had irregular changing trendwith different pyrolysis temperature and duration time, but that of biochar derivedfrom soybean stalk declined with the increasing pyrolysis temperature and durationtime.By the method of laboratory experiment, we set a batch of Albic soil and Blacksoil columns to study the effects of applying biochar derived from corn cob on thevolume of leachate, soil pH, the loss of ammonium nitrogen (NH4+-N) and nitratenitrogen (NO－3-N). We found biochar can effectively increase water-holding capacityand soil pH. Adding2%biochar significantly decreased the N leachate in Albic soiland Black soil by12%and15%, respectively. While when4%biochar was added, theN leachate in Albic soil and Black soil decreased by13%and5%, respectively,compared with the treatments of adding2%biochar. Fertilizer adsorbed by biocharand then mixed with soil significantly decreased the N leachate compared to soilmixed with fertilizer and biochar directly. The effects of biochar derived from corn cob had different effects on decreasing the N leachate among different N fertilizers. InAlbic soil, compared with the treatment of no biochar added, adding2%biochardecreased the N leachate of ammonium sulfate, potassium nitrate and urea by8%,15%and12%, respectively. While in the Black soil, they decreased by5%,18%and12%,respectively.The soil enzyme activities in the soybean rhizosphere treated with three dosagesof biochar derived from corn stalk, i.e.2%(C2),4%(C4) and8%(C8), wereinvestigated. Results indicated that the enzyme activities were related to the type ofthe soils and soybean growth stages. Results indicated that biochar increased theinvertase and urease activites in treatments C2, C4and C8compared with no addingcontrol (CK). Low content of bichar is beneficial to increase phosphatase activity,while the high biochar content inhibited phosphatase activity. In Black soils, theeffects of biochar on invertase activity were not obvious, e.g. no obvious effects oninvertase, phosphatase and catalase activities in C2; the urease increased in treatmentsC4and C8compared with the control and phosphatase and catalase activitiessignificantly reduced.The numbers of cultured microorganisms in soybean rhizosphere at the growthstages of flowering, pod-setting and seed filling were calculated by plating method.Results indicated that adding biochar increased the number of bacteria, actinomycetesand fungi in the Albic soil and Black soil.Effect of biochar on the microbial community functional diversity in soybeanrhizosphere samples at growth stage of seed filling was investigated by using theBiolog method. The results showed that the ability of microbes using carbon scourcesin biochar treatment in Albic soil was higher than that in CK during the entireincubation period; while in Black soil, there were no obvious differences between C4and CK, but decreased significantly in C2and C8. By compared the utilization of31kinds of carbon sources, microorganism community catabolic diversities of C4andC8evaluated by Shannon index (H), substrate richness (S) and Evenness index (E),respectivly were significantly higher than thoseof CK in the Albic soil, but there wasno obvious changes between C2and CK. While no significant changes in Black soil.By calculating the ultimate load value of the31carbon sources, we found treatmentswith different amount of biochar could use different carbon sources in Albic soil andBlack soil.Compared with control, appliying biochar promoted the soybean growth and increased plant height, fresh/dry weight of aboveground part and underground part,the number of nodule and crop yield in Albic soil. However, biochar only increasedthe fresh/dry weight of root and the number of nodule, but no obvious effects on plantheight and fresh/dry weight of aboveground part and underground part in Black soil.The application of biochar significantly increased root length, root volume and rootarea both in Albic soil and Black soil.