Abstract The CO2 flush is recommended as an indicator of soil biological health. We conducted field and greenhouse experiments to evaluate the effect of several factors likely to influence C mineralization (presence/absence of plants, plant species, time of season, N fertility) on the CO2 flush. The field experiment was conducted with barley grown in 2017 (two sampling times) and 2018 (three sampling times). In greenhouse experiments, barley was grown for 4, 6, or 8 weeks; barley, corn, crimson clover, soybean, and ryegrass were grown for 4 weeks; and corn and barley were grown for 5 weeks at 4 levels of N. All had unplanted controls. Root biomass, microbial biomass carbon (MBC), dissolved organic carbon (DOC), and the amount of CO2-C released during 24 h after rewetting dried soil were measured. MBC was determined by the microwave method, and DOC was extracted by water with C quantified using a Shimadzu TOC-VCPH. A LI-COR infrared gas analyzer was used to quantify CO2. We found that planted soil had a greater CO2 flush than bare or unplanted soil, but the difference was not large, ranging between 15 and 40%. Root biomass did not consistently correlate with the CO2 flush. In unfertilized soils, the CO2 flush was not influenced by plant species. In fertilized soils, the CO2 flush was significantly higher in soils planted to corn than soils planted to barley at the two highest nitrogen levels. We found strong correlations between DOC and the CO2 flush, and inconsistent correlations between MBC and the CO2 flush. Because the CO2 flush was not strongly influenced by collection time, plant species, or N fertility, the CO2 flush may be a robust soil health indicator among different crops and sampling times.

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评估 CO2 冲洗作为土壤健康指标

摘要 CO2 冲洗被推荐作为土壤生物健康的指标。我们进行了田间和温室实验，以评估可能影响 C 矿化的几个因素（植物的存在/不存在、植物种类、季节时间、氮肥力）对 CO2 冲洗的影响。田间试验使用 2017 年（两次采样）和 2018 年（三次采样）种植的大麦进行。在温室试验中，大麦种植 4、6 或 8 周；大麦、玉米、深红三叶草、大豆和黑麦草种植了 4 周；玉米和大麦在 4 个 N 水平下生长 5 周。所有对照均未种植。测量根生物量、微生物生物量碳 (MBC)、溶解有机碳 (DOC) 和再润湿干燥土壤后 24 小时内释放的 CO2-C 量。MBC 用微波法测定，和 DOC 用水提取，C 使用 Shimadzu TOC-VCPH 定量。LI-COR 红外气体分析仪用于量化 CO2。我们发现种植的土壤比裸露或未种植的土壤具有更大的 CO2 冲洗，但差异并不大，在 15% 到 40% 之间。根生物量与 CO2 冲洗不一致。在未施肥的土壤中，CO2 冲洗不受植物种类的影响。在施肥土壤中，在两种最高氮水平下，种植玉米的土壤中的 CO2 冲洗量明显高于种植大麦的土壤。我们发现 DOC 和 CO2 冲洗之间有很强的相关性，而 MBC 和 CO2 冲洗之间的相关性不一致。因为 CO2 冲洗不受收集时间、植物种类或 N 肥力的强烈影响，