长期不同施肥复垦土壤大团聚体中各有机碳组分的变化特征

研究采煤塌陷区复垦土壤大团聚体中各有机碳组分的变化特征对不同施肥措施的响应,从而更好地理解土壤有机碳固持机制,并为该区域改善土壤质量、提升土壤肥力提供科学依据。通过采集复垦6 a定位试验不同施肥处理0~20 cm土层土样,采用物理分组法,分析土壤大团聚体中各有机碳组分(粗颗粒有机碳(cPOC)、细颗粒有机碳(fPOC)、大团聚体中微团聚体内颗粒有机碳(iPOC)以及矿质结合态有机碳(MOC)组分)的变化特征及其与土壤有机碳之间的关系。试验包括不施肥(CK)、施化肥(NPK)、单施有机肥(M)以及有机无机肥配施(MNPK)4个处理。研究结果表明,同CK相比,施NPK肥对大团聚体中各组分的有机碳含量均无显著影响;而M处理显著降低了MOC含量,达36.45%;MNPK处理显著提高了cPOC和f POC含量,分别是CK的4倍和2倍,但是显著降低了MOC含量,达39.01%。4个组分中,仅有cPOC和fPOC含量与SOC含量呈显著正相关,说明复垦土壤有机碳首先固存于未受保护的有机碳组分中。CK,NPK,M和MNPK处理下土壤固碳速率分别为0.82,0.68,1.36和1.58 mg/(ha·a)。土壤固碳速率与年均碳投入量呈显著的线性相关关系(R²=0.58,P<0.05),每年约有31%的投入碳转化到土壤中。综合来看,采煤塌陷区复垦土壤仍有一定的空间固存有机碳,有机无机肥配施是提升该区域土壤有机碳含量的有效途径,增加的有机碳优先固存于未受保护的有机碳组分中。

Variation characteristics of organic carbon fractions within macroaggregates under long-term different fertilization regimes in the reclaimed soil

To better understand the mechanism of soil organic carbon(SOC)sequestration and provide a scientific basis for improving soil fertility and quality in the reclaimed coal-mining subsiding region,it was investigated the response of variation characteristics of organic carbon(OC)fractions within macroaggregate to fertilization regimes in the reclaimed soil.Topsoil samples(0-20 cm)were collected from the different treatments of a 6-year reclaimed field.The variation characteristics of OC fractions within macroaggregates(coarse particulate organic carbon referred to as cPOC,fine particulate organic carbon referred to as f POC,intra-microaggregate particulate organic carbon referred to as i POC and mineral associated organic carbon referred to as MOC)and relationships between them and SOC concentration were analyzed using physical fractionation method.Four different fertilization treatments were no fertilizer(CK),chemical fertilizer with nitrogen,phosphorus and potassium(NPK),organic manure alone(M)and chemical fertilizer combined with manure(MNPK).Compared with CK,the application of chemical fertilizers(NPK)had no effect on the OC contents in any macroaggregate fractions.However,the application of manure alone(M)significantly decreased MOC content by 36.45%.Application of manure combined with chemical fertilizers(MNPK)markedly increased cPOC and f POC contents,which were 4 and 2 times higher than CK,but it greatly decreased MOC content by39.01%.Among the four fractions,only cPOC and f POC contents were significantly positively correlated with SOC concentration,indicating that SOC was primarily sequestered in the unprotected OC fractions within macroaggregates in the reclaimed soil.The SOC sequestration rates in the treatments of CK,NPK,M and MNPK are 0.82,0.68,1.36 and 1.58 mg/(ha·a).SOC sequestration rate was significantly positively correlated with annual carbon input(R²=0.58,P<0.01),and about 31%of input carbon sank into the soil every year.In conclusion,there is still more space to storage SOC,the combination of organic manure and chemical fertilizers is the most effective practice to promote SOC storage,the increased OC is preferentially sequestered in the unprotected OC fractions.