| Biochar produced from agricultural waste during high temperature at non-oxygen or lower oxygen is anew substance, which can improve the fertility of poor yield soil. Grey desert soil (GDS) is the mainagricultural soil in Xinjiang and its white, knottsclay and drought properties can not make better use of thenitrogen (N) fertilizer. The cotton stalk (CS) accounted for a third of agricultural waste straw in Xinjiangand returned directly to soil was likely to lead to degradation of soil quality. However, the cotton stalkbiochar (CSB) CS pyrolized return to GDS is a new method to improve soil fertility. Therefore, the papertook the CS to pyrolyze by muffle furnace, which to discuss the relationships of the pyrolysis temperature(300,450,600℃) and time (0.5,1,2,4,6h) and the CSB properties. The effects of the CSB amount onGDS properties and N mineralization and nitrification were tested by laboratory incubation experiments.The effects of the CSB amount on maize growth and N use efficiency at different levels of N fertilizer werediscussed by pot experiment in GDS-maize cropping system. The results showed:(1) The ratio of CSB to CS and organic carbon (OC) content of CSB decreased with the pyrolysistemperature and time increasing. With the time extended, the pH value of the CSB increased at300℃andkept around10.5at450and600℃. The electricity conductivity (EC) of CSB increased with the pyrolysistemperature increasing, and its change was not significant in pyrolysis time. The pyrolysis temperaturebetween300and450℃imposed less on EC, but the effect in600℃was significant. The cation exchangecapacity (CEC) of the CSB decreased with the pyrolysis temperature increasing and increased at300℃but decreased at450and600℃with the pyrolysis time extending. The phosphorus (P), potassium (K)content of CSB increased but N decreased with pyrolysis temperature increasing or time extending. Thecorrelations between pyrolysis temperature or time and the ratio of CSB to CS, CEC, OC, N were negative,but positive for pH value, P and K in CSB.(2) The pH value, EC and OC, available P (AP), available K (AK) content of GDS increased with CSBamount increasing. However, the effects of CSB amount (0,0.5,1.0,2.0%) on CEC, total NPK were notsignificant. The pH value of GDS decreased over incubation days. The EC, alkaline N (AN) and APdecreased during former incubation stage and turned stability. The CEC increased slowly over days. TheOC, total N (TN), total P (TP) and AK of GDS had no significant change during80incubation days.(3) The N mineralization and nitrification amounts of GDS decreased with an increase in CSB rate (0,0.1,0.5,1.0,2.0%) during first week, and the decrease extent of N mineralization was higher than that of N nitrification. The N mineralization amount of GDS added with600℃CSB (CSB600) was significanthigher than that of300℃CSB (CSB300) at the same rate of CSB addition. However, the N mineralizationof GDS added with CSB300almost occurred during second week and changed not significant betweentreatments. Conversely, the N nitrification amounts of GDS with and without CSB reached above80percent and had no significant difference between treatments. The nitrification rate reached above95%after two weeks.(4) The effect of CSB on N uptake efficiency by maize was not significant under different N fertilizer levelin GDS-maize cropping system (P>0.05). There was a negative effect of CSB on maize growth in no Nfertilizer treatments but it turned to positive effect and increased with the amount of CSB after N fertilizeraddition. The N uptake by maize in N150was higher than that of N200treatments but not significant eitherat the same rate of CSB addition. the N use efficiency of1%CSB amendment was slight higher than anytreatments in N150and the highest N use efficiency was in0.5%CSB treatment in N200. The N useefficiency of N150,1%CSB and N200,0.5%CSB treatments increased by3%than that of their controlsoils without CSB addition. |
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