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1. Diversified rotations improved yield performance and profitability in a 16‐year, no‐input experiment

   https://doi.org/10.1002/agj2.70502  

   Ebrahimi, Elnaz; McDaniel, Marshall D; Grandy, A Stuart; Haddad, Nick; Smith, Richard G; Gross, Katherine L; Robertson, G Philip (July 2026, Agronomy Journal)

   Abstract Diversified crop rotations offer multiple agroecosystem benefits like closing yield gaps, reducing environmental impact, improving resiliency, and enhancing farm profitability. We used data from a 16‐year crop rotation experiment in SW Michigan that was conducted with no external agrochemical inputs to isolate and evaluate the “crop rotation effect” on grain yields, the relative yield gap compared to county‐level means, and profitability. Treatments were maize (Zea maysL.), soybean (Glycine maxL. merr.), and winter wheat (Triticum aestivumL.) systematically diversified in combination with one another and non‐harvested winter cover crops (red clover [Trifolium pratenseL.] or crimson clover [T. incarnatumL.] and cereal rye [Secale cerealeL.]). Across all three cash crops, adding any crop in rotation reduced relative yield gaps compared to monocrops by ∼77%, 20%, and 58% for maize, soybean, and winter wheat, respectively. Diversified rotations, particularly those including leguminous cover crops, increased maize and winter wheat grain yields by up to 95% and 64% relative to 2‐ and 3‐year rotations without legume cover crops and improved economic returns (>300%). Diversified rotations provided measurable productivity and economic gains in the absence of confounding management practices that have historically obscured the rotation effect. 

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2. Data from: Long-term changes in soil carbon and nitrogen fractions in switchgrass, native grasses, and no-till corn bioenergy production systems

   https://doi.org/10.5061/dryad.547d7wmf3  

   Perry, Sophie; Falvo, Grant; Mosier, Samantha; Robertson, Philip G. (January 2023, Dryad)

   Abstract: Cellulosic bioenergy is a primary land-based climate mitigation strategy, with soil carbon (C) storage and nitrogen (N) conservation as important mitigation elements. Here, we present 13 years of soil C and N change under three cellulosic cropping systems: monoculture switchgrass (Panicum virgatum L.), a five native grasses polyculture, and no-till corn (Zea mays L.). Soil C and N fractions were measured four times over 12 years. Bulk soil C in the 0–25 cm depth at the end of the study period ranged from 28.4 (± 1.4 se) Mg C ha−1 in no-till corn, to 30.8 (± 1.4) Mg C ha−1 in switchgrass, and to 34.8 (± 1.4) Mg C ha−1 in native grasses. Mineral-associated organic matter (MAOM) ranged from 60% to 90% and particulate organic matter (POM) from 10% to 40% of total soil C. Over 12 years, total C as well as both C fractions persisted under no-till corn and switchgrass and increased under native grasses. In contrast, POM N stocks decreased 33% to 45% across systems, whereas MAOM N decreased by less than 13% and only in no-till corn. Declining POM N stocks likely reflect pre-establishment land use, which included alfalfa and manure in earlier rotations. Root production and large soil aggregate formation explained 69% (p < 0.001) and 36% (p = 0.024) of total soil C change, respectively, and 60% (p = 0.020) and 41% (p = 0.023) of soil N change, demonstrating the importance of belowground productivity and soil aggregates for producing and protecting soil C and conserving soil N. Differences between switchgrass and native grasses also indicate a dependence on plant diversity. Soil C and N benefits of bioenergy crops depend strongly on root productivity and pre-establishment land use. Methods: See the Materials and Methods of the associated publication for procedures on sampling and processing, and section 2.9 Statistical analysis for statistical models. The R software was used for all analyses (R Core Team, 2014); the R scripts are provided in the file Statistical_Analysis.R. R Core Team. (2014). R: A language and environment for statistical computing. R Foundation for Statistical Computing. http://www.Rproject.org/ 

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3. Phosphorus budgets of intensively managed row crops at a long‐term agroecosystem research site in the upper US Midwest

   https://doi.org/10.1002/jeq2.70000  

   Hussain, Mir Zaman; Hamilton, Stephen K; Basso, Bruno; Robertson, G Philip (February 2025, Journal of Environmental Quality)

   Abstract Phosphorus (P) budgets for cropping systems provide insights for keeping soil P at optimal levels for crops while avoiding excess inputs. We quantified 12 years of P inputs (fertilizer and atmospheric deposition) and outputs (harvest and leaching losses) for replicated maize (Zea maysL.)—soybean (Glycine maxL.)—wheat (Triticum aestivum) crop rotations under conventional, no‐till, reduced input, and biologically based (organic without compost or manure) management systems at the Kellogg Biological Station LTAR site in southwest Michigan. Conventional, no‐till, and reduced input systems were fertilized between 13 and 50 kg P ha⁻¹depending on year. Soil test phosphorus (STP) was measured at 0‐ to 25‐cm depth every autumn. Leached P was measured as dissolved P in the soil solution sampled beneath the rooting depth and combined with modeled percolation. Fertilization and harvest were the predominant P fluxes in the fertilized systems, whereas only harvest dominated P flux in the unfertilized organic system. Leaching losses were minor terms in the budgets, but leachate concentrations were nevertheless close to the range of concern for downstream eutrophication. Over the 12‐year study period, the organic system exhibited a negative P balance (−82.0 kg P ha⁻¹), coinciding with suboptimal STP levels, suggesting a need for P supplementation. In contrast, the fertilized systems showed positive P balances (mean: 70.1 kg P ha⁻¹) with STP levels well above agronomic optima. Results underscore the importance of tailored P management strategies to sustain crop productivity while mitigating environmental impacts. 

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4. Butterfly biodiversity increases with prairie strips and conservation management in row crop agriculture

   https://doi.org/10.1111/icad.12675  

   Kemmerling, Lindsey R.; McCarthy, Annabelle C.; Brown, Cameron S.; Haddad, Nick M. (August 2023, Insect Conservation and Diversity)

   Saunders, M; Bell, J (Ed.)

   Abstract Butterfly abundances are declining globally, with meta‐analysis showing a rate of −2% per year. Agriculture contributes to butterfly decline through habitat loss and degradation. Prairie strips—strips of farmland actively restored to native perennial vegetation—are a conservation practice with the potential to mitigate biodiversity loss, but their impact on butterfly biodiversity is not known. Working within a 30‐year‐old experiment that varied land use intensity, from natural areas to croplands (maize–soy–wheat rotation), we introduced prairie strips to less intensely managed crop treatments. Treatments included conservation land, biologically based (organic) row crops with prairie strips, reduced input row crops with prairie strips, no‐till row crops and conventional row crops. We measured butterfly abundance and richness: (1) within prairie strips and (2) across the gradient of land use intensity at the plot level. Butterfly abundance was higher within prairie strips than in all other treatments. Across the land use intensity gradient at the plot level, the conservation land treatment had the highest abundance, treatments with prairie strips had intermediate levels and no‐till and conventional treatments had the lowest abundances. Also across entire plots, butterfly richness increased as land use intensity decreased. Treatments with prairie strips, which also had reduced land use intensity, had distinct butterfly communities as they harboured several butterfly species that were not found in other row crop treatments. In addition to the known effects of prairie strips on ecosystem services including erosion control and increased water quality, prairie strips can increase biodiversity in multifunctional landscapes. 

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5. Characterizing Dominant Field-Scale Cropping Sequences for a Potato and Vegetable Growing Region in Central Wisconsin

   https://doi.org/10.3390/land11020273  

   Heineman, Emily Marrs; Kucharik, Christopher J. (February 2022, Land)

   Crop rotations are known to improve soil health by replenishing lost nutrients, increasing organic matter, improving microbial activity, and reducing disease risk and weed pressure. We characterized the spatial distribution of crops and dominant field-scale cropping sequences from 2008 to 2019 for the Wisconsin Central Sands (WCS) region, a major producer of potato and vegetables in the U.S. The dominant two- and three-year rotations were determined, with an additional focus on assessing regional potato rotation management. Our results suggest corn and soybean are the two most widely planted crops, occurring on 67% and 36% of all agricultural land at least once during the study period. The most frequent two- and three-year crop rotations include corn, soybean, alfalfa, sweet corn, potato, and beans, with continuous corn being the most dominant two- and three-year rotations (13.2% and 8.5% of agricultural land, respectively). While four- and five-year rotations for potato are recommended to combat pest and disease pressure, 23.2% and 65.9% of potato fields returned to that crop in rotation after two and three years, respectively. Furthermore, 5.6% of potato fields were planted continuously with that crop. Given potato’s high nitrogen (N) fertilizer requirements, the prevalence of sandy soils, and ongoing water quality issues, adopting more widespread use of four- or five-year rotations of potato with crops that require zero or less N fertilizer could reduce groundwater nitrate concentrations and improve water quality. 

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