Tillage practices are known to influence soil stratification, but crop rotation can strongly affect fluxes of energy and matter, and thus play a role in determining soil organic matter (SOM) fate. Using a high-resolution stratified soil sampling at 2.5 cm intervals from 0 to 30 cm depth, we evaluated the half century impacts of tillage and crop rotation on SOM stratification, and how specific soil organic functional groups drive SOM accrual in typical USA Midwest agroecosystems. Three levels of tillage intensity—no-tillage, chisel, and moldboard, and three crop rotations—continuous-corn, 2-year corn-soybean, and 3-year corn-forage-forage—were evaluated at two sites with contrasting soil characteristics (silt-loam versus clay-loam). Soil organic matter concentration was determined by loss on ignition and soil organic functional group abundances were estimated by diffuse reflectance infrared Fourier transform spectroscopy (mid-DRIFTS). No-tillage systems had a more stratified distribution of SOM than in more intensive tillage systems, with greater SOM concentrations in the uppermost layers of silt-loam (0−10 cm, 9.4–20% change to chisel/moldboard) and clay-loam soils (0−30 cm, 12–15% change). Under no-tillage, crop rotation with forage maintained or increased SOM accrual (0–17.5/20 cm, -0.9–22% change to other rotations), but including soybean in the rotation diminished SOM accrual when compared to continuous-corn (-8 to -12 % change) or corn-forage rotation (-11 to -18 % change). Abating tillage increased abundance of aliphatic and phenol in the uppermost soil layers, and these organic functional groups were primarily driving SOM accrual, while SOM was inversely related to more recalcitrant functional groups (aromatic, carbonyl, and carboxylate). Soil organic functional groups (65.4 % of R²) and soil type, sampling depth, and management (34.6 % of R²) accurately predicted SOM concentrations (R² = 93.4) underscoring their importance as a pathway to SOM accrual. Minimizing tillage intensity and rotating perennial forages in corn-based agricultural systems may lead to greater organic resource abundance that drive SOM accrual. This may present additional benefits to soil health, plant roots, and soil organisms in conservative agricultural systems.

耕作方法会影响土壤分层，但轮作会强烈影响能量和物质的通量，因此在决定土壤有机物（SOM）命运方面发挥了作用。使用从0到30厘米深度的2.5厘米间隔的高分辨率分层土壤采样，我们评估了耕作和农作物轮作对SOM分层的半个世纪影响，以及特定土壤有机官能团如何驱动典型的美国中西部农业生态系统中SOM的累积。在两个具有不同土壤特性的地点评估了三种耕作强度（免耕，凿子和mold板）和三种轮作（连续玉米，2年玉米-大豆和3年玉米-草料-草料） （粉质壤土与黏土壤土）。通过灼烧损失确定土壤有机质浓度，并通过漫反射红外傅里叶变换光谱法（mid-DRIFTS）估算土壤有机官能团的丰度。免耕系统的SOM分布比更密集的耕作系统更为分层，在粉壤土（0-10厘米，凿子/刨花板的最上层变化为9.4-20％）和黏土壤土的最上层中，SOM的浓度更高土壤（0-30厘米，变化12-15％）。在免耕条件下，以牧草进行的轮作维持或提高了SOM应计成本（0-1.75 / 20厘米，其他轮作变化为-0.9–22％），但与连续玉米相比，轮作中包括大豆降低了SOM的应计成本（- 8至-12％的变化）或玉米草料轮换（-11至-18％的变化）。减少耕作增加了最上层土壤中脂肪和苯酚的含量，这些有机官能团主要推动了SOM的增长，而SOM与更顽固的官能团（芳族，羰基和羧酸盐）呈负相关。土壤有机官能团（R的65.4％²）和土壤类型，采样深度和管理（R ^2的34.6％）准确预测了SOM浓度（R ² = 93.4），强调了它们作为SOM累积途径的重要性。在以玉米为基础的农业系统中，尽量减少耕种强度和轮作多年生牧草，可能会导致更多的有机资源丰富，从而推动SOM的累积。这可能会给保守农业系统中的土壤健康，植物根和土壤生物带来更多好处。