Obour Peter Bilson, Jensen Johannes L, Lamandé Mathieu, Watts Christopher W, Munkholm Lars J
Department of Agroecology, Aarhus University, Research Centre Foulum, Blichers Allé 20, P.O. Box 50, DK-8830, Tjele, Denmark.
Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003 NMBU, 1432, Ås, Norway.
Soil Tillage Res. 2018 Oct;182:57-65. doi: 10.1016/j.still.2018.05.001.
The effects of soil organic matter on the water contents for tillage were investigated by sampling soils with a uniform texture, but a range of soil organic carbon (SOC) from two long-term field experiments at Highfield in Rothamsted Research, UK and Askov Experimental Station, Denmark. The treatments studied in Highfield were Bare fallow (BF), Continuous arable rotation (A), Ley-arable (LA) and Grass (G); and in Askov: unfertilized (UNF), ½ mineral fertilizer (½ NPK), 1 mineral fertilizer (1NPK), and 1½ animal manure (1½AM). Minimally disturbed soil cores (100 cm) were sampled per plot in both locations from 6 to 10 cm depth to generate water retention data. Soil blocks were also sampled at 6-15 cm depth to determine basic soil properties and to measure soil aggregate strength parameters. The range of soil water contents appropriate for tillage were determined using the water retention and the consistency approaches. SOC content in Highfield was in the order: G > LA = A > BF, and in Askov: 1½ AM > 1NPK = ½NPK > UNF. Results showed that different long-term management of the silt loam Highfield soil, and fertilization of the sandy loam Askov soil affected the mechanical properties of the soils- for Highfield soil, aggregates from the G treatment were stronger in terms of rupture energy when wet (-100 hPa matric potential) than the BF treatment. As the soil dried (-300 and -1000 hPa matric potentials), soil aggregates from the G treatment were relatively weaker and more elastic than the BF soil. Our study showed, for both Highfield and Askov soils, a strong positive linear increase in the range of water contents for tillage with increasing contents of SOC. This suggests that management practices leading to increased SOC can improve soil workability by increasing the range of water contents for tillage. We recommended using the consistency approach over the water retention approach for determining the range of water contents for tillage because it seems to give realistic estimates of the water contents for tillage.
通过对质地均匀但土壤有机碳（SOC）含量范围不同的土壤进行采样，研究了土壤有机质对耕作含水量的影响。这些土壤样本取自英国洛桑试验站的海菲尔德和丹麦阿斯克夫实验站的两个长期田间试验。在海菲尔德研究的处理方式有裸地休耕（BF）、连续耕作轮作（A）、草地-耕地轮作（LA）和草地（G）；在阿斯克夫的处理方式有不施肥（UNF）、半量矿物肥料（½ NPK）、全量矿物肥料（1NPK）和1.5倍动物粪便（1.5AM）。在这两个地点，每个地块均从6至10厘米深度采集最少扰动的土芯（100厘米）以获取持水数据。还在6 - 15厘米深度采集土块，以确定基本土壤性质并测量土壤团聚体强度参数。使用持水和稠度方法确定适合耕作的土壤含水量范围。海菲尔德的SOC含量顺序为：G＞LA = A＞BF，阿斯克夫的顺序为：1.5AM＞1NPK = ½NPK＞UNF。结果表明，粉砂壤土海菲尔德土壤的不同长期管理方式以及砂壤土阿斯克夫土壤的施肥处理会影响土壤的力学性质——对于海菲尔德土壤，在湿润状态下（-100 hPa基质势），G处理的团聚体在破裂能量方面比BF处理更强。随着土壤变干（-300和-1000 hPa基质势），G处理的土壤团聚体比BF土壤相对更弱且更具弹性。我们的研究表明，对于海菲尔德和阿斯克夫土壤，随着SOC含量增加，适合耕作的含水量范围呈强烈的正线性增加。这表明导致SOC增加的管理措施可以通过扩大适合耕作的含水量范围来改善土壤可耕性。我们建议在确定适合耕作的含水量范围时使用稠度方法而非持水方法，因为它似乎能给出更符合实际的耕作含水量估计值。
