有机肥替代化肥对旱地黄壤有机碳矿化及活性有机碳的影响

Effects of Organic Fertilizer Replacing Chemical Fertilizer on Organic Carbon Mineralization and Active Organic Carbon in Dryland Yellow Soil

目前有机肥替代化肥对旱地黄壤有机碳矿化及活性有机碳的影响特征及机制还不够明确.为探究有机肥替代化肥对旱地黄壤有机碳矿化及活性有机碳的的影响,采集施肥处理为:不施肥(CK)、单施化肥(NP)、50%有机肥替代化肥[1/2(NPM)]和100%有机肥替代化肥(M)的土壤进行有机碳室内矿化培养研究,探究有机肥替代化肥条件下土壤有机碳变化特征及活性有机碳变化.结果表明,有机肥替代化肥显著提高土壤pH、有机碳(SOC)、全氮(TN)和C/N.培养期间,各处理土壤有机碳矿化速率均表现为初期(第2~4 d)大幅下降,中期(第4~20 d)小幅度下降,末期(第20~60 d)趋近于平稳.施肥后土壤有机碳累积矿化量显著增加了7.9%~27.7%,与NP处理相比,1/2(NPM)处理土壤有机碳累积矿化量降低了5.2%,M处理则增加了12.2%.矿化培养前,有机肥替代化肥对土壤易氧化有机碳(ROC)无显著影响,显著增加了微生物量碳(MBC)含量,1/2(NPM)处理显著增加可溶性有机碳(DOC)含量,M处理则显著降低.培养60 d后,各处理土壤活性有机碳含量较初始含量均有所减少,其中MBC减少量最多,为30.6%~41.2%.有机碳累积矿化量与土壤pH和SOC呈显著正相关,与MBC初始值及培养前后的变化值呈极显著正相关.综上,100%有机肥替代化肥显著促进土壤有机碳矿化,降低土壤有机碳的稳定性;50%有机肥替代化肥抑制土壤有机碳矿化,有利于土壤固碳培肥;50%有机肥替代化肥显著增加土壤活性有机碳含量,MBC在土壤有机碳矿化过程中被作为主要碳源所利用.

At present,the effect characteristics and mechanism of organic fertilizer replacing chemical fertilizer on organic carbon mineralization and active organic carbon in dryland yellow soil remain unclear.In order to explore the effect of organic fertilizer replacing chemical fertilizer on organic carbon mineralization and active organic carbon in dryland yellow soil,we used soil with no fertilization(CK),only chemical fertilizer(NP),50%organic fertilizer replacing chemical fertilizer(1/2(NPM)),and 100%organic fertilizer replacing chemical fertilizer(M).We examined the indoor mineralization culture of organic carbon and explored the characteristics of soil organic carbon and the change in active organic carbon under the condition of organic fertilizer replacing chemical fertilizer.The results showed that organic fertilizer replacing chemical fertilizer increased soil pH,organic carbon(SOC),total nitrogen(TN),and C/N.During the culture period,the soil organic carbon mineralization rate of all treatments decreased sharply in the initial stage(2-4 days),decreased slightly in the middle stage(4-20 days),and tended to be stable in the last stage(20-60 days).After fertilization,the cumulative mineralization of soil organic carbon significantly increased by 7.9%-27.7%.Compared with that in the NP treatment,the cumulative mineralization of soil organic carbon decreased by 5.2%in the 1/2(NPM)treatment and increased by 12.2%in the 1/2(NPM)treatment.Before mineralization culture,the substitution of organic fertilizer for chemical fertilizer had no significant effect on soil recalcitrant organic carbon(ROC)but significantly increased the content of microbial biomass carbon(MBC).The content of dissolved organic carbon(DOC)was significantly increased in the 1/2(NPM)treatment and decreased in the M treatment.After 60 days of culture,the content of soil active organic carbon in all treatments decreased compared with the initial content,of which MBC decreased the most(30.6%-41.2%).The accumulated mineralization of organic carbon was significantly positively correlated with soil pH and SOC and significantly positively correlated with the initial value of MBC and the change value before and after culture.To summarize,100%organic fertilizer replacing chemical fertilizer significantly promoted soil organic carbon mineralization and reduced soil organic carbon stability;50%organic fertilizer replacing chemical fertilizer inhibited soil organic carbon mineralization,which was beneficial to soil sequestration and fertilization;and 50%organic fertilizer replacing chemical fertilizer significantly increased soil active organic carbon content,and MBC was used as the main carbon source in the process of soil organic carbon mineralization.