施用小麦秸秆或其生物炭对烟田土壤理化特性及有机碳组分的影响

  【目的】  以2年田间定位试验为依托，研究小麦秸秆及其生物炭连续施用对植烟土壤理化性状和有机碳组分的影响，为烟区土壤质量提升提供依据。  【方法】  田间试验在山东省诸城市潮褐土烟田上进行。试验设4个处理，分别为:常规施肥且秸秆不还田(CK)，常规施肥+小麦秸秆还田(FS)，常规施肥+小麦秸秆生物炭2.25 t/hm2 (FB1)和4.50 t/hm2 (FB2)。在烟叶收获后，采集0—20 cm耕层土样，测定了土壤基础理化指标和总有机碳(TOC)、微生物生物量碳(MBC)、热水溶性有机碳(HWC)、活性有机碳(LOC)及轻组有机碳(LFOC)含量，并计算土壤碳库管理指数(CPMI)。  【结果】  连续施用小麦秸秆或其生物炭2年后，FB1和FB2处理TOC含量显著高于CK，增幅分别为74.9%和116.0%，而FS与CK处理间差异不显著。LFOC含量的变化趋势与TOC类似，FB1和FB2处理LFOC含量分别较CK处理显著增加154%和326%。FS处理HWC含量显著高于CK和FB1处理，而与FB2处理差异不显著。与CK相比，FS处理HWC含量增加了107%。FS和FB2处理MBC含量较CK分别增加了252%和144%，而FB1处理与CK相比差异不显著。FS处理LOC含量较CK显著增加了68.9%，而FB1、FB2处理LOC含量与CK相比差异不显著。FS处理还能显著降低土壤容重、增加土壤含水量及有效磷含量，其对部分土壤理化特性的改良效果优于生物炭处理(FB1和FB2)。此外，CPMI也以FS处理最高，较CK显著增加了73.5%，而FB1、FB2处理与CK处理差异不显著。  【结论】  连续秸秆还田有利于提升烟田土壤活性有机碳(MBC、HWC和LOC)含量，降低土壤容重，提高有效磷含量，提高土壤CPMI。而同量秸秆转化为生物炭后连续还田能够提高土壤总有机碳和轻组有机碳含量，更有利于土壤有机碳的长期固存。

Effects of wheat straw and its biochar application on soil physiochemical properties and organic carbon fractions in flue-cured tobacco field

  【Objectives】  To understand the effects of wheat straw and its biochar on soil physiochemical properties and organic carbon fractions to provide basis for improvement of flue-cured tobacco planting soil.  【Methods】  A two-year field experiment was carried on the meadow-cinnamon soil in 2016 and 2017 in Zhucheng, Shandong Province. Four treatments were designed, namely, chemical fertilizer alone (CK), chemical fertilizer plus wheat straw (FS), chemical fertilizer plus biochar of 2.25 t/hm2 (FB1), and 4.50 t/hm2 (FB2). At tobacco harvest, soil samples were collected in the plough layer (0?20 cm), and soil physiochemical properties and contents of microbial biomass C (MBC), hot-water extractable C (HWC), labile organic C (LOC), light fraction organic C (LFOC), and carbon pool management index (CPMI) were investigated.  【Results】  The TOC contents in FB1 and FB2 was 74.9% and 116.0% significantly higher than that in CK, whereas no significant difference was found between FS and CK. The variation trend of LFOC in the four treatments was similar to that of TOC, and LFOC content in FB1 and FB2 was 154% and 326% significantly higher than that in CK. No significant difference in HWC content was observed between FS and FB2, while HWC content in FS treatment was significantly higher than that in FB1 and CK. In comparison with CK, HWC content in FS was increased by 107%. MBC content in FS and FB2 was significantly higher by 252% and 144% than that in CK, but no significant difference was found between FB1 and CK. LOC content in FS was significantly increased by 68.9% compared to that in CK, while no significant difference was found among FB1, FB2 and CK treatments. In addition, wheat straw returning (FS) significantly decreased soil bulk density and increased soil water content and soil available P content, which had a better effect on some soil physical and chemical properties than those of biochar treatments. The FS treatment also had the highest value of CPMI, which was 73.5% significantly higher than that of CK. However, the biochar treatments (FB1 and FB2) decreased or changed a little CPMI in comparison with CK.  【Conclusions】  The continuous incorporation of wheat straw could increase the contents of soil labile organic carbon fractions of MBC, HWC and LOC, improve soil physiochemical properties, whereas wheat straw biochar could increase the stability of soil organic carbon, which is beneficial for the long-term stable fixation of soil organic carbon.