陇中黄土高原不同草田轮作模式土壤碳组分的差异研究

通过田间定位试验,研究黄土高原西部旱农区多年生苜蓿草地(L-L)及苜蓿耕翻轮作处理苜蓿-休闲(L-F)、苜蓿-小麦(L-W)、苜蓿-玉米(L-C)、苜蓿-马铃薯(L-P)、苜蓿-谷子(L-M)对土壤总有机碳(TOC)、易氧化有机碳(ROC)、轻组有机碳(LFOC)及重组有机碳(HFOC)的影响。结果表明,在0200 cm土层,不同轮作模式下土壤总有机碳含量及土壤各有机碳组分均表现为随土层加深呈波动下降趋势,其中TOC、ROC、HFOC含量最高值和最低值分别出现在苜蓿连作表层(05 cm) 和苜蓿轮作(小麦)中层(3050 cm) ,LFOC最高值和最低值分别出现在苜蓿轮作(马铃薯)表层(05 cm)和苜蓿轮作(玉米)底层(170200 cm)。与苜蓿连作模式相比,苜蓿轮作(小麦、玉米、马铃薯、谷子)会降低TOC、ROC、HFOC含量,增加LFOC含量,其中TOC含量分别降低17.44%,9.25%,18.40%和9.34%;ROC含量分别降低28.10%,8.52%,29.75%和23.17%;HFOC含量分别降低18.80%,10.06%,20.53%和12.50%;LFOC分别增加7.41%,5.56%,22.22%和57.41%。可见,苜蓿种植多年耕翻轮作粮食作物后降低了土壤总有机碳水平,且对有机碳各组分的影响存在显著差异。

Soil carbon fraction differences under different grass-crop rotations on the Loess Plateau,Central Gansu

Field experiments investigating the effect of continuous lucerne (Medicago sativa )(L-L)and five ro-tation systems lucerne-fallow (L-F),lucerne-wheat (L-W),lucerne-corn (L-C),lucerne-potato (L-P),lu-cerne-millet (L-M)]on total organic carbon (TOC),readily oxidation organic carbon (ROC),light fraction or-ganic carbon (LFOC)and heavy fraction organic carbon (HFOC)in a typical arid area of the Western Loess Plateau.The results showed that under different rotation systems TOC and soil organic carbon fractions de-creased with increasing soil depth (0 -200 cm soil depth).The highest TOC,ROC and HFOC values were found in the surface soil layer (0-5 cm)under the L-L rotation system,and the lowest values at mid depths(30-50 cm)under the L-W rotation system.The highest and lowest values for LFOC were found in the sur-face soil layer (0-5 cm)under the L-P rotation and the bottom soil layer (170-200 cm)under the L-C rota-tion,respectively.Compared with L-L rotation,the L-W,L-C,L-P and L-M rotations reduced TOC by 17.4%,9.3%,18.4% and 9.3%,respectively.Similarly,ROC was reduced by 28.1%,8.5%,28.1% and 23.2% and HFOC by 18.8%,10.1%,20.5% and 12.5% respectively.However,LFOC increased by 7.4%, 5.3%,22.2% and 57.4% under L-W,L-C,L-P and L-M rotations,respectively.It was concluded that lu-cerne-grain rotation systems reduce TOC.