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Based on the11-year long-term experiments in Dingxi, western Loess Plateau, theeffects of conventional tillage (T) and5conservation tillage practices [no-till with stubbleretention (NTS), conventional tillage with stubble incorporation (TS), no-till and no-stubbleretention (NT), no-till with plastic mulching (NTP) and conventional tillage with plasticmulching (TP)] on total organic carbon(TOC), readily oxidizable organic carbon(ROOC)and light fraction organic carbon (LFOC) of loess soil were studied. The aim was to explorethe different effects among mulching methods and the connection with the lever ofproductive forces, provided the basis of make the soil quality development by towardshealthy way. The main conclusions were as follows:1. This research finding, in the year of2002to2012，the average content of TOC under NTS,NT, NTP and TS were increased. However, the content of TOC and ROOC under T and TPwere sharp decline. The content of TOC under NTS in spring wheat-field pea-spring wheatrotation sequence and field pea-spring wheat-field pea rotation sequence were respectiveincreased by9.5%and8.9%、13.2%and11.5%、21.5%and8.8%、2.7%and2.1%in2004,2006,2008and2012. The average content of ROOC under NTS in both rotationsequences were respective increased by42.9%and33.2%、67.6%and59.6%、71.5%and49.5%、12.6%and1.7%in2004,2006,2008and2012. The content of LFOC under NTS andTS were respective increased by15.8%and23.1%、10%and17.6%、13.9%and18.7%、41.6%and83.5%in2004,2006,2008and2012.2. Compared with T, the treatments of NTS and TS increased the content of TOC、ROOCand LFOC. These results show that NTS and TS were beneficial to accumulate of TOC andROOC, especially the treatment of NTS. It was clear that the treatment of NTS was benefitto development healthy ecological agriculture by increase the quality of soil in westernLoess Plateau.The content of TOC and ROOC in long-term treatment of TP was lower thanT. TP respective reduced TOC by4.3%and0.1%, ROOC by2.7%and4.6%, LFOC by2.3%.3. The results showed that, with the increasing of soil depth, the content of TOC、ROOC andLFOC were decreased. The content of TOC, ROOC, LFOC were8.0~9.4g/kg,4.4~5.5g/kg and0.11~0.13g/kg in0-5cm.7.8~9.0g/kg,4.2~5.1g/kg and0.1~0.12g/kg in5-10cm.7.3~8.1g/kg,4.1~4.9g/kg and0.06~0.07g/kg in10-30cm. It’s plain to see the content of TOC in10-30cm less than0-5cm.4. Active organic carbons were more sensitive response to long-term tillage. Compare withTOC, the change under ROOC and LFOC respectively faster2~5and2~13times. However,further research need to confirm whether they were the best indicators.
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