不同有机肥施用模式下黄壤稻田根际和非根际土壤有机碳的矿化特征

Organic carbon mineralization characteristics in rhizosphere and bulk soil of rice under organic fertilization modes in yellow paddy fields

【目的】研究长期施用有机肥对土壤有机碳矿化特征的影响,为提高土壤碳库稳定性和培肥土壤提供理论依据。【方法】贵阳黄壤肥力与肥效长期定位试验始于1994年,种植制度为单季水稻。2021年水稻收获后,选取不施肥(CK),平衡施用化肥(NPK),25%和50%有机肥氮替代化肥氮(0.25MNPK、0.5MNPK)和单施有机肥(M)5个处理的水稻植株,用抖根法采集根际和非根际土壤样品,分析活性碳组分含量,以采集的土样进行室内培养试验,研究有机碳矿化特征。【结果】1)与NPK相比,3个有机肥处理的根际土壤有机碳(SOC)含量提升了26%~43%,非根际土壤SOC含量提高了24%~32%;根际土壤微生物量碳(MBC)含量提升了16%~31%,且比非根际土壤高148%;非根际土壤易氧化有机碳(LOC)含量显著提升了36%~75%;0.5MNPK处理非根际土壤可溶性有机碳(DOC)含量显著提升了54%,且根际土壤的DOC含量平均高于非根际土壤10%。2)有机肥施用可明显增加黄壤稻田根际及非根际土壤有机碳矿化量,非根际土壤有机碳矿化量和矿化率分别高于根际土壤30%和33%;较CK和NPK处理,有机肥施用明显增加了根际土壤有机碳矿化量;与NPK处理相比,各有机肥处理有机碳矿化量增加了36%~63%,其与有机肥施用量成正比;NPK处理有机碳矿化量较CK降低,且在非根际土中更明显;非根际土壤中有机碳累计矿化率以CK最高,各有机肥处理较CK降低了19%~28%。3)土壤有机碳累积矿化量随培养天数的动态变化过程符合一级动力学方程。根际土壤中,M处理提升了有机碳累积矿化量(Ct),各施肥处理的潜在可矿化有机碳量(C0)提升了1.44~3.23倍;0.25MNPK和0.5MNPK处理明显降低了有机碳库日周转速率常数k。与NPK处理相比,其他处理均明显提升了非根际土壤Ct,0.25MNPK增加了C0,0.25MNPK和0.5MNPK明显降低了k值。4)根际和非根际土壤中,Ct与SOC、LOC、DOC含量均呈显著正相关关系,但与qMB(SMB/SOC)显著负相关。【结论】25%~50%有机肥氮替代化肥氮能显著提升土壤有机碳稳定性,增加土壤碳储量并减少碳损失,是黄壤稻田碳库管理及土壤培肥的优选施肥模式。

【Objectives】Study of the effects of organic fertilization on soil organic carbon mineralization characteristics could elucidate the soil carbon pool change and stable mechanism of yellow paddy fields.【Methods】The long-term experiment of fertility and fertilizer efficiency of Guiyang was established in 1994,with mono-rice planting system.In 2021,rhizosphere and bulk soils of rice were collected from the five treatments for the determination of soil total and active carbon fraction contents.Including the control(no fertilizer,CK),balanced application of chemical fertilizer(NPK),25%and 50%organic fertilizer nitrogen instead of chemical fertilizer nitrogen(0.25MNPK,0.5MNPK)and single organic fertilizer(M).A indoor incubation experiment was conducted using the soils for determination of organic carbon mineralization amount and kinetic mineralization parameters.【Results】1)Compared with NPK,organic fertilizer treatments(0.25MNPK,0.5MNPK,M)increased soil organic carbon(SOC)in rhizosphere and bulk soil by 26%−43%and 24%−32%,and microbial biomass carbon(MBC)in rhizosphere soil by 16%−31%,and the MBC in rhizosphere soil was 148%higher than bulk soil.Compared with NPK,contents of liable organic carbon(LOC)in bulk soils was significantly increased by 36%−75%under organic fertilizer treatments.Dissolved organic carbon(DOC)content was significantly increased by 54%in bulk soil under 0.5MNPK treatment,and DOC in rhizosphere soil was 10%higher than that of bulk soil.2)Organic fertilizer treatments significantly increased SOC mineralization in rhizosphere and bulk soils,and the mineralization amount and rate in bulk soil were 30%and 33%higher than in rhizosphere soil,respectively.Compared with CK and NPK,organic fertilizer treatments significantly increased rhizosphere SOC mineralization by 36%−63%,which was proportional to the application amount of organic fertilizer.NPK treatment recorded lower mineralization amount than CK,but its variation with CK was more pronounced in bulk soil.CK elicited the highest cumulative mineralization rate in bulk soil,which was 19%−28%higher than organic fertilizer treatments.3)The dynamics of cumulative SOC mineralization amount with incubation time fit the first-order kinetic equation.In rhizosphere soils,treatment M increased the cumulative mineralization of organic carbon(Ct),while 0.25MNPK and 0.5MNPK treatments increased potential mineralizable organic carbon(C0)by 1.44−3.23 times of CK.0.25MNPK and 0.5MNPK treatments significantly reduced the turnover rate of organic carbon pool per day constant k.Compared with NPK,Ct was significantly increased in bulk soil,C0 was significantly increased by 0.25MNPK treatment,and k value was significantly reduced under 0.25MNPK and 0.5MNPK treatments.4)Ct was significantly and positively correlated with SOC,LOC,and DOC contents,but both were significantly and negatively correlated with qMB(SMB/SOC)in rhizosphere and bulk soils.【Conclusions】In sum,25%to 50%organic nitrogen substitution are the preferred fertilization modes for carbon pool management and soil fertilization in yellow paddy fields,for it markedly increases the stability of soil organic carbon,carbon storage,and reduces carbon loss.