不同水分条件下添加白云石对酸性水稻土有机碳矿化的影响

施用石灰改良酸性土壤是常用的农艺措施之一。施用石灰影响土壤理化性质,进而影响土壤有机碳(Soil Organic Carbon,SOC)矿化。而SOC矿化与土壤肥力保持和有机碳库的大小存在紧密联系。因此,明晰施用石灰对酸性土壤有机碳矿化的影响具有重要的理论和现实意义。该研究以2种母质的酸性水稻土为对象,在50%、90%和130%土壤最大田间持水量(Water Holding Capacity,WHC)条件下添加和不添加白云石,再进行为期45 d的室内培养试验,探讨白云石和水分对SOC矿化的影响。研究结果表明,添加白云石显著影响2种土壤有机碳矿化速率,但白云石添加和水分的交互作用不显著。土壤含水量较低时(50%WHC),2种土壤有机碳矿化均受到抑制。在较高土壤含水量情况下(90%～130%WHC),白云石添加和水分的共同作用对SOC矿化的影响因土壤质地不同而异,淹水条件下(130%WHC)棕红壤有机碳矿化量高于湿润条件(90%WHC),而红壤中的情况正好相反。白云石添加和水分均显著影响SOC累计矿化量,但二者交互作用仅在棕红壤中显著。添加白云石后,2种土壤pH值随着水分含量的增加而提高;土壤含水量较低时(50%WHC),土壤pH值即可达到或接近目标值(pH值6.5)。这些结果表明,在评估施用白云石对SOC矿化的影响时,需要考虑土壤含水量和土壤本身的性质,以便为农业生产实践中合理施用白云石提供指导和建议。

Effects of dolomite addition on organic carbon mineralization in acidic paddy soils under different moisture contents

Liming is the most widely used for the soil acidity, further to maintain soil pH that is optimal for crop growth. The variation in the soil pH is closely related to the soil organic carbon (SOC) mineralization, thereby to the global climate change. In addition, the moisture is also one of the most crucial environmental factors influencing the SOC mineralization via changing the SOC bioavailability and oxygen transport. In response to exogenous additives, the physicochemical and biochemical properties of soils are normally different with distinct parent materials. It is necessary to clarify the effects of liming and moisture on organic carbon mineralization of acidic soils. In the present study, the acidic paddy soils with two parent materials were used to evaluate the effects of dolomite addition and moisture on the SOC mineralization. Two types of soils were treated with and without dolomite addition under different soil moisture conditions, including 50%, 90%, and 130% of water holding capacity (WHC), and further incubated for 45 days. The results showed that the SOC mineralization rates of two soils were significantly affected by the dolomite addition. Nevertheless, there was no remarkable interaction effect between dolomite addition and moisture. The organic carbon mineralization of two soils was inhibited under a low soil moisture of 50% WHC, whereas, the combined effects of dolomite addition and moisture on the SOC mineralization varied with soil texture under a high soil moisture of 90% to 130% WHC. The amount of organic carbon mineralization from the soil with granite gneiss as parent material (brown red soil) under flooding condition (130% WHC) was higher than that under the moisture of 90% WHC, while the scenario was the opposite from the soil with the Quaternary red earth as parent material (red soil). Furthermore, only the former soil demonstrated a significant interaction effect of dolomite addition and moisture on the amount of SOC mineralization. The effects of dolomite addition, moisture, and their interaction were significant on the pH of two soils. After dolomite addition, the pH value of two soils increased with the increase in moisture content, where a target value (pH 6.5) was achieved under a low soil moisture condition (50% WHC). The effects of dolomite addition and moisture were significant on the DOC content of brown red soil, but their interaction was not significant. Moreover, only the effect of moisture on the DOC content of red soil was significant. The MBC contents of two soils increased significantly with the increase of moisture content, but the effects of dolomite addition and its interaction with moisture were not significant. In the path analysis, the DOC rather than MBC content of two soils was directly affected by the soil pH value. In addition, the fluxes of CO2 emission in the two soils were directly affected by the DOC rather than MBC content. The soil pH had no direct effect on the fluxes of CO2 emission in the two soils, indicating that the microbes played a major role in CO2 emissions. Therefore, both soil moisture and natural properties can be considered to evaluate the effect of dolomite application on SOC mineralization. The finding can provide a potential promising guidance and proposals for the rational application of dolomite additives in the agricultural production.