地膜覆盖麦田土壤有机碳矿化特征及其温度敏感性

【目的】明确旱地土壤有机碳矿化对地膜长期覆盖的响应及有机碳矿化的温度敏感性,进而深入理解土壤有机碳的转化与稳定机制,为旱地土壤培肥和作物增产提供理论支撑。【方法】在黄土高原东南部2012年开始的旱地小麦田间地膜覆盖试验的基础上,采集不同覆盖栽培模式（常规施肥（不覆膜）、测控施肥（不覆膜）、垄膜沟播（覆膜）、平膜穴播（覆膜））试验的0—20 cm土层土壤样品,采用不同温度（15、25和35℃）进行室内有机碳矿化培养实验。在培养后的第1、3、5、7、14、21、28、35和42天运用碱液吸收法测定土壤有机碳矿化速率,结合双库指数模型拟合土壤活性和惰性有机碳库的容量及其分解速率,研究地膜覆盖对土壤有机碳矿化特征的影响及有机碳矿化对温度变化的响应规律。【结果】温度升高显著提高了土壤有机碳矿化速率、累积矿化量和惰性有机碳库（Cs）的矿化量,但是显著降低了温度敏感性系数（Q₁₀）和活化能（Ea）。25℃和35℃时土壤有机碳矿化速率和累积矿化量均无显著差异,分别为15℃时的2倍,Cs的矿化量分别较15℃时提高了93.4%和105.3%。但是Q₁₀（25-35℃）比Q₁₀（15-25℃）降低了19.3%,Ea（25-35℃）比Ea（15-25℃）同步降低了68.0%。地膜覆盖显著提高了土壤有机碳累积矿化量、Q₁₀、Ea以及Cs的矿化量。同常规施肥相比,垄膜沟播和平膜穴播均显著提高了土壤有机碳累积矿化量,增幅分别为26.5%—38.6%（25℃）和27.8%—64.4%（35℃）,且以平膜穴播提升幅度最大;平膜穴播处理亦显著提高了Q₁₀和Ea,其中Q₁₀增幅分别为28.5%（15—25℃）和25.8%（25—35℃）,Ea增幅分别为93.4%和193.1%;平膜穴播处理还显著提高了Cs的矿化量,增幅达115.8%—2 208.2%。【结论】黄土高原旱地麦田土壤上地膜覆盖加速了土壤有机碳矿化,尤其是平膜穴播,主要通过增加惰性有机碳库的矿化,进而显著提高了土壤有机碳累积矿化量及其温度敏感性。

Mineralization Characteristics of Soil Organic Carbon and Its Temperature Sensitivity in Wheat Field Under Film Mulching

【Objective】Clarify the response of dryland soil organic carbon (SOC) mineralization to long-term film mulching and its temperature sensitivity, and further understand the transformation and stabilization mechanism of SOC, providing theoretical support for dryland soil fertility and crop productivity. 【Method】Based on the dryland wheat field mulching experiment that began in 2012 in the southeastern of the Loess Plateau, soil samples of 0-20 cm layer for different mulching cultivation modes (farmer’s practice fertilization (no film mulching), monitoring fertilization (no film mulching), monitoring fertilization plus ridge mulching-furrow planting (mulching), and monitoring fertilization plus whole field film (mulching)) were collected, and then the soil samples were incubated at different temperatures (15, 25 and 35℃). The lye absorption method was used to determine the SOC mineralization rate at the 1^st, 3^rd, 5^th, 7^th, 14^th, 21^st, 28^th, 35^th and 42^th days after incubation, combined with two component model to fit the cumulative mineralization and decomposition rate of soil active and recalcitrant organic carbon pool, investigate the effect of film mulching on SOC mineralization characteristics and the response of SOC mineralization to temperature.【Result】The results showed that the increasing temperature had significantly increased SOC mineralization rate, cumulative mineralization and the mineralization amount of recalcitrant organic carbon pool (Cs), but markedly decreased the temperature sensitivity (Q₁₀) and activation energy (Ea). The mineralization rate and cumulative mineralization of SOC at 25℃ and 35℃ were about twice that at 15℃, and the mineralization of Cs increased by 93.4% and 105.3% respectively compared with that at 15℃. But Q₁₀ (25-35℃) is 19.3% lower than Q₁₀ (15-25℃), and Ea (25-35℃) is 68.0% lower than Ea (15-25℃). Plastic film mulching significantly increased the SOC cumulative mineralization, the mineralization of Q₁₀, Ea and Cs. Compared with farmer fertilization treatment, both monitoring fertilization plus ridge mulching-furrow planting and monitoring fertilization plus whole field film treatments had significantly increased the SOC cumulative mineralization by 26.5%-38.6% (25℃) and 27.8%-64.4% (35℃), respectively, while monitoring fertilization plus whole field film treatment had the largest improvement. The monitoring fertilization plus whole field film treatment had also significantly increased Q₁₀ by 28.5% (15-25℃) and 25.8% (25-35℃) and Ea by 93.4% and 193.1%, respectively. Furthermore, monitoring fertilization plus whole field film treatment had markedly increased the mineralization amount of Cs by 115.8%-2 208.2%. 【Conclusion】Therefore, film mulching accelerated the SOC mineralization in the dryland wheat field of the Loess Plateau, especially for monitoring fertilization plus whole filed filming treatment mainly increased the mineralization of recalcitrant organic carbon pool, and then significantly increased the cumulative mineralization of SOC and its temperature sensitivity.