This study investigated changes in soil physical quality and water dynamics arising from continuous cropping at the Morrow Plots, the oldest agricultural experiment in North America. The objectives were to examine the effects of continuous cultivation on soil water retention and determine the optimum water content for tillage (θOPT) in a prime agricultural soil. Soil samples collected at 0–5, 5–10, and 10–15 cm depths were used to measure bulk density and water retention using the HyProp 2 and WP4-T Dewpoint Potentiometer. Soil organic carbon (SOC) and soil penetration resistance (PR) were measured to a depth of 15 cm. The soil water retention data were fitted with the Dexter double exponential and van Genuchten models. Neither model consistently fitted all the water retention data across the different management practices. The corn-oat-hay (COH) rotation generally reduced soil bulk density within the 0–15 cm depth by an average of 9 % and PR by 21 % compared to the continuous corn (CC) treatment. The COH rotation slightly increased topsoil water-holding capacity (0–15 cm), although trends varied with fertility regimes. The θOPT for the COH and CC estimated by the van Genuchten model was generally wetter than the water content at field capacity (θFC). In contrast, the θOPT estimated by the Dexter model was slightly drier than θFC. Despite limitations due to the lack of true replicates and the small sample size at the Morrow Plots, this research underscores the long-term impact of crop rotation on soil hydraulic properties in prime agricultural soils.

中文翻译：

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Morrow Plots 不同管理制度下的土壤物理性质和水动态


本研究调查了北美最古老的农业实验 Morrow Lots 连作引起的土壤物理质量和水动力学变化。目的是检查连续耕作对土壤保水的影响，并确定优质农业土壤中最适合耕作的含水量 （θOPT）。使用 HyProp 2 和 WP4-T 露点电位计，在 0-5、5-10 和 10-15 cm 深度收集的土壤样品用于测量体积密度和保水性。土壤有机碳 （SOC） 和土壤渗透阻力 （PR） 测量深度为 15 cm。土壤保水数据采用 Dexter 双指数和 van Genuchten 模型拟合。两种模型都不能一致地拟合不同管理实践中的所有保水数据。与连续玉米 （CC） 处理相比，玉米-燕麦-干草 （COH） 轮作通常使 0-15 cm 深度内的土壤容重平均降低 9 %，PR 降低 21 %。COH 轮换略微增加了表层土壤持水能力 （0-15 cm），尽管趋势随肥力状况而变化。van Genuchten 模型估计的 COH 和 CC 的 θOPT 通常比现场容量下的含水量 （θFC） 更湿润。相比之下，Dexter 模型估计的 θOPT 比 θFC 略干。尽管由于缺乏真正的重复和 Morrow Lots 的样本量小而存在限制，但这项研究强调了作物轮作对优质农业土壤土壤水力特性的长期影响。