title: Sequestration of maize crop straw C in different soils: role of oxyhydrates in chemical binding and stabilization as recalcitrance.
abstract: While biophysical controls on the sequestration capacity of soils have been well addressed with physical protection, chemical binding and stabilization processes as well as microbial community changes, the role of chemical binding and stabilization has not yet well characterized for soil organic carbon (SOC) sequestration in rice paddies. In this study, a 6-month laboratory incubation with and without maize straw amendment (MSA) was conducted using topsoil samples from soils with different clay mineralogy and free oxy-hydrate contents collected across Southern China. The increase in SOC under MSA was found coincident with that in Fe- and Al-bound OC (Fe/Al-OC) after incubation for 30 d (R(2)=0.90, P=0.05), and with sodium dithionate-citrate-bicarbonate (DCB) extractable Fe after incubation for 180 d (R(2)=0.99, P<0.01). The increase in SOC under MSA was found higher in soils rich in DCB extractable Fe than those poor in DCB extractable Fe. The greater SOC sequestration in soils rich in DCB extractable Fe was further supported by the higher abundance of (13)C which was a natural signature of MSA. Moreover, a weak positive correlation of the increased SOC under MSA with the increased humin (R(2)=0.87, P=0.06) observed after incubation for 180 d may indicate a chemical stabilization of sequestered SOC as humin in the long run. These results improved our understanding of SOC sequestration in China's rice paddies that involves an initial chemical binding of amended C and a final stabilization as recalcitrant C of humin.
authors.affiliation: Institute of Resource, Ecosystem and Environment of Agriculture, Nanjing Agricultural University, Nanjing 210095, PR China.
authors.forename: Xiangyun
authors.initials: X
authors.lastname: Song
authors.forename: Lianqing
authors.initials: L
authors.lastname: Li
authors.forename: Jufeng
authors.initials: J
authors.lastname: Zheng
authors.forename: Genxing
authors.initials: G
authors.lastname: Pan
authors.forename: Xuhui
authors.initials: X
authors.lastname: Zhang
authors.forename: Jinwei
authors.initials: J
authors.lastname: Zheng
authors.forename: Qaiser
authors.initials: Q
authors.lastname: Hussain
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Han
authors.forename: Xinyan
authors.initials: X
authors.lastname: Yu
mesh_terms: D000535:Aluminum / Q000737:chemistry; D002244:Carbon / Q000032:analysis*; D057965:Carbon Sequestration; D007501:Iron / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry; D012987:Soil / Q000737:chemistry*; D003313:Zea mays / Q000737:chemistry*
chemical_list: D012987:Soil; D002244:Carbon; D000535:Aluminum; D007501:Iron; D010100:Oxygen