Dotun Arije, Prakriti Bista, and Rajan Ghimire used the DayCent biogeochemical model to simulate 25 years of a no-till winter wheat–sorghum–fallow rotation on the Southern High Plains, testing five management scenarios against two climate futures. Their findings, published in the Journal of Agriculture and Food Research, reveal a partial and crop-specific decoupling between soil organic carbon accumulation and grain yield — a finding that could reshape how dryland farmers think about cover cropping.

The stakes are high. In the western United States, decades of continuous cropping, extensive fallow periods with less than 40 percent precipitation storage efficiency, and residue removal have depleted soil organic carbon and reduced the soil’s water-holding capacity. Cover cropping has been widely promoted as a remedy, but its effects on subsequent cash crop yields remain highly context-dependent. A global meta-analysis of 154 studies found that while cover crops significantly increased soil organic carbon and reduced nitrogen leaching, they reduced grain yields by roughly 4 percent on average — a penalty that grows more severe in water-limited environments where soil moisture is the primary constraint on production.

Field studies in dryland wheat–sorghum rotations of western Kansas showed wheat yield reductions of 25 to 31 percent following spring-planted cover crops, while sorghum yields were approximately 11 percent lower compared with fallow. Similar patterns have been observed globally, with cover crops reducing precipitation storage efficiency by 13 to 33 percent and causing maize yield penalties of up to 18 percent in dry years. Yet in systems where water and nitrogen are not co-limiting, cover crops can simultaneously enhance soil carbon and productivity — legume-based cover cropping in the semi-arid Great Plains increased soil organic carbon by 20 to 30 percent while improving sorghum yields, and no-till maize–soybean rotations with vetch cover crops in the Argentinean Rolling Pampas reported yield increases of 12 to 30 percent alongside enhanced soil carbon.

To untangle these contradictions, the researchers built their modeling framework on an ongoing long-term experiment at the NMSU Agricultural Science Center in Clovis, New Mexico, on Olton clay loam soil under no-tillage management with limited irrigation providing roughly half of crop water requirements. The simulations were initialized with a 2000-year spin-up under native prairie conditions to establish equilibrium soil carbon pools, followed by historical land-use transitions reflecting regional agricultural development. The model was calibrated using a stepwise procedure adjusting potential productivity, temperature response functions, harvest index, and lignin content, then validated against observed yields and soil carbon trends using multiple statistical metrics including RMSE, normalized RMSE, R², Nash–Sutcliffe efficiency, and mean bias error.

The researchers evaluated five management scenarios: total dryland with no irrigation, early cover crop termination that shortened the cover phase from roughly 90 to 60 days, early termination combined with early sorghum planting shifted from early June to early May, a modified sorghum irrigation regime that redistributed water from three 50-millimeter applications to five 30-millimeter applications while keeping the seasonal total constant, and early termination combined with the modified irrigation regime. Each scenario was implemented with a pea monoculture and a pea–oat–canola multi-species mixture, compared with a limited-irrigation fallow baseline under both a continued historical climate scenario extending observed 1985–2024 weather patterns and an SSP5–8.5 high-emission scenario derived from three CMIP6 Earth System Models and bias-corrected using quantile mapping.

The results were striking. Pea-based systems produced the highest average soil organic carbon across all scenarios, ranging from 2058 to 2223 grams of carbon per square meter, while the multi-species mixture systems were lower at 1799 to 1995 grams per square meter and fallow systems showed intermediate values. The highest soil carbon levels occurred under early sorghum planting combined with early cover crop termination and under the modified irrigation regime, particularly for pea treatments under both climate pathways. Total dryland systems showed the lowest soil carbon across all treatments. Under the high-emission scenario, soil carbon was consistently 1.5 to 4.5 percent lower than under the continued historical climate for the same treatment combinations, though the relative ranking among management strategies remained similar.

Yield responses told a more complicated story. Sorghum yield under the high-emission scenario was 22 to 63 percent lower than under the continued historical climate, while wheat responses ranged from a 10 percent reduction to an 8 percent increase depending on management and treatment. The baseline fallow system generally maintained the highest sorghum grain yield at 423.8 grams of carbon per square meter per harvest, while pea treatments consistently produced lower sorghum yields of typically 160 to 260 grams per square meter under continued climate. In contrast, wheat grain yield was highest under pea treatments across all management scenarios, reaching up to 206.4 grams of carbon per square meter per harvest under early cover crop termination. Total dryland systems had the lowest grain yields and biomass for both crops under both climate pathways, with sorghum yields declining to 86 to 108 grams per square meter under high-emission conditions and wheat yields dropping below 60 grams per square meter.

To synthesize these multidimensional outcomes, the researchers applied a Composite Performance Index that standardized soil carbon, sorghum yield, and wheat yield using z-scores and averaged them with equal weighting. The early cover crop termination plus early sorghum planting scenario produced the highest index value of 0.92, followed by early termination alone at 0.89 and early termination combined with modified irrigation at 0.87 — all pea-based systems under the continued historical climate. These top-ranked combinations were characterized by high soil carbon contributions and strongly positive wheat responses, while sorghum responses remained near neutral. Under the high-emission scenario, the same pea-based management combinations remained the highest-ranked systems, though index values declined to between 0.51 and 0.66 because of reduced sorghum performance. Total dryland systems consistently ranked among the lowest performers under both climate pathways, with the worst outcome observed in total dryland multi-species mixture systems under the high-emission scenario at an index of negative 1.60, with negative scores across all three indicators.

The soil carbon pool distribution provided mechanistic insight into where these gains reside. Across all scenarios, the passive pool accounted for roughly 56 to 64 percent of total soil organic carbon and showed little variation over time, while the slow pool represented roughly 34 to 38 percent and increased across all scenarios. The active pool remained small at roughly 1.5 to 2.6 percent, and the litter fraction ranged from roughly 1.1 to 3.1 percent. Total soil carbon increases were associated primarily with accumulation in the slow pool — intermediate-turnover carbon rather than substantial accumulation in the passive pool. The highest slow pool proportions, up to roughly 38 percent, occurred under early sorghum planting and modified irrigation regimes, particularly in pea systems under both climate pathways, coinciding with the highest total soil carbon values.

The contrasting responses of pea to subsequent crops demonstrate that greater soil carbon accumulation may not always correspond to greater system-level productivity. The crop-specific responses likely reflect differences in crop growth duration, resource demand, and timing within the rotation. The relatively short interval between cover crop termination and sorghum establishment may constrain soil water availability at planting, while the longer interval before wheat planting may partly explain the more stable wheat yield responses. Early cover crop termination and supplemental irrigation for sorghum appear to support cover crop residue decomposition and nutrient supply while minimizing water stress during early sorghum growth, which is critical for higher sorghum yield.

Under the high-emission scenario, elevated temperatures likely increased evapotranspiration and crop water stress, which have previously been associated with reduced productivity in semi-arid systems. Elevated temperatures may also accelerate crop development and shorten grain-filling duration, further reducing yield potential. Although modified irrigation and early termination strategies partially reduced yield penalties under the high-emission scenario, none fully compensated for the combined effects of increased evaporative demand and reduced soil water availability. Across both climate pathways, yield responses appeared more strongly influenced by water availability and management timing than by total soil carbon alone, as soil carbon gains did not consistently correspond to increased grain yield, particularly for sorghum under water-limited conditions.

The researchers acknowledge several limitations. The Composite Performance Index assumed equal importance of soil carbon, sorghum yield, and wheat yield; alternative weighting based on production priorities, yield stability, or water-use efficiency could alter scenario rankings. Including economic feasibility of additional costs for cover crop planting, management, and termination would also be needed to fully assess alternative scenarios. The scenario comparisons are subject to model uncertainty because the modified management scenarios extend beyond the combinations used for DayCent calibration, particularly where predicted differences are small. The default DayCent configuration does not represent dynamic atmospheric CO₂ fertilization, which could affect crop and soil carbon responses, particularly given differences between the responsiveness of C3 and C4 crops. Although DayCent simulates nitrogen cycling, this study did not evaluate nitrogen-related outputs and therefore cannot directly infer the contributions of biological nitrogen fixation, mineral nitrogen availability, immobilization, and nitrogen losses to crop-specific responses. The study also did not quantify soil water availability at crop establishment, so yield response to post-termination water recovery remains plausible rather than a demonstrated mechanism.

Nevertheless, the findings carry significant implications for dryland agriculture. The poor performance of dryland cover cropping systems in this study emphasizes the importance of water availability and the need to align cover crop management with subsequent crop establishment. Climate pathways exerted a stronger influence on system performance than individual management modifications, highlighting the potential for greater uncertainty under changing climate and increasing drought frequency and intensity in dry environments. Although management adjustments could reduce the magnitude of these responses, none fully offset the effects in high-emission pathways, demonstrating the limited capacity of management alone to overcome climate-driven constraints.

For farmers weighing the risks of cover cropping in water-limited environments, the study offers a nuanced message: soil carbon gains are achievable, but they require crop-specific optimization that current cover crop management strategies alone are unlikely to deliver without additional interventions. The research was funded by project 2022-67019-36106 of the USDA National Institute for Food and Agriculture’s Agriculture and Food Research Initiative, with additional support from the USDA Southwest Climate Hub.

Subject of Research: Soil Organic Carbon–Yield Tradeoffs under Alternative Cover Crop Management in a Semi-Arid Cropping System

Article Title: Soil Organic Carbon–Yield Tradeoffs under Alternative Cover Crop Management in a Semi-Arid Cropping System

Article References: Arije, D., Bista, P., & Ghimire, R. (2026). Soil Organic Carbon–Yield Tradeoffs under Alternative Cover Crop Management in a Semi-Arid Cropping System. Journal of Agriculture and Food Research, Article 103373. https://doi.org/10.1016/j.jafr.2026.103373

Image Credits: AI Generated

DOI: 10.1016/j.jafr.2026.103373

Keywords: Soil, Organic, Carbon, Yield, Tradeoffs, under, Alternative, Cover, Crop, Management, Semi-Arid, Cropping