Curtis J. Dell

Interseeding annual forages into growing corn may be an alternative for both cover and grazing in temperate regions of the United States. A 4‐year experiment evaluated the effect of interseeding cereal rye (Secale cereale) into corn for grazing after harvest on corn grain, forage biomass yield and quality, soil health, and estimated spatial biomass yields using vegetation indices (VIs) from multispectral imagery collected from an unmanned aircraft system platform. Corn was planted (79,074 plants ha⁻¹) each spring on two 4.8‐ha sites in central Pennsylvania. Cereal rye was interseeded (135 kg ha⁻¹) into corn at the V4–V6 stage. Corn was harvested as grain in November, and each site was subdivided and randomly assigned to grazed or non‐grazed treatments. Biomass yield and quality, soil samples, and estimates of biomass yield using VIs from multispectral imagery monitoring occurred in fall and spring. Results indicated that cereal rye plus corn stover provided enough forage for an additional 105–130 animal unit days ha⁻¹ with minimal impact on soil health indicators. Vegetative indices varied in the ability to predict biomass yield; all VIs except normalized difference red edge saturated at ∼2 Mg ha⁻¹. Spring growth of cereal rye was much less dependable than fall. Corn grain yields did not decrease (averaging 9.9 tonnes of dry matter ha⁻¹) as a result of grazing or due to continuous corn planting except in 2019 (dry year) when corn grain yields were reduced by 35%–40%. Interseeding cereal rye into corn that is harvested as grain can be a viable method to establish a cover crop to extend the grazing season without impairing cash crop yield.

Long‐term research is essential for guiding the development of agroecosystems to meet escalating production demands in a manner that is environmentally sound and socially acceptable. Research must integrate biophysical and socioeconomic factors to provide geographically scalable knowledge that involves stakeholders across the research‐education‐extension‐policy spectrum. In response to this need, the Long‐Term Agroecosystem Research (LTAR) network developed a “Common Experiment,” which seeks to develop and disseminate multi‐region, science‐based information to enable implementation of visionary agricultural innovations while simultaneously promoting food security, well‐being, environmental quality, and climate adaptation and mitigation. The core design of the Common Experiment contrasts prevailing and alternative/aspirational production systems, with the latter including novel innovations hypothesized to advance sustainable intensification in locally appropriate ways. Treatments in the Common Experiment represent a diversity of production systems under cropland, grazing land, and integrated crop/grazing land management. Where possible, treatments are evaluated at multiple spatial scales (e.g., from plot to enterprise) and are designed to evolve over the course of the experiment with stakeholder input. A common assessment framework guides data collection for the experiment and is complemented by metric‐specific protocols and an emerging data management infrastructure. Currently, there are large differences among sites in the application of the experimental framework and degree of stakeholder engagement; differences largely grounded in pragmatic issues related to land access, site expertise, and resource availability. The full potential of the LTAR Common Experiment may be realized with strategic investments in network capacity.

Dairy production is a key agricultural enterprise in the Upper Chesapeake Bay (UCB) basin, where phosphorous (P) and nitrogen (N) loading contribute to eutrophication. Import of forages and grains and application of mineral fertilizers contribute to nutrient imbalances in the basin. The UCB Long‐Term Agroecosystem Research Cropland Common Experiment aims to evaluate diverse crop rotations that minimize the need for imported feed, maximize year‐round living cover, and reduce nutrient losses. UCB's plot‐scale experiment was established in 2018, incorporating an ongoing cropping system study that was established by the Pennsylvania State University in 2010. An alternative dairy cropping rotation (including silage and grain corn [Zea mayes L.], alfalfa [Medicago sativa L.]/orchardgrass [Dactylis glomerata L.] mix, winter rye silage [Secale cereale L.], and sorghum‐sudangrass [Sorghum × drummondii (Steud.) Millsp. & Chas]) that employed manure injection, integrated pest management, and less frequent manure application was compared to a prevailing, conventionally managed silage corn–alfalfa rotation with higher manure application rates. A field‐scale experiment was established in 2019 to monitor alternative production practices (manure injection and avoidance of neonicotinoid seed treatment) and prevailing practices in three fields on a commercial dairy farm. Findings suggest that crop rotation diversification, manure injection, and integrated pest management have the potential to increase the economic and environmental sustainability of dairy cropping systems, but long‐term evaluation is needed for confirmation.

Corn (Zea mays) crops harvested as grain in autumn do not provide opportunity for cover crop establishment, which may be remedied by interseeding cover crops into growing corn. Grazing cover crops after corn grain harvest could provide added revenues and increase nutrient cycling in the system while providing additional ecosystem services. However, tradeoffs between cash crop productivity and cover crop inclusion, and use as grazed forage, are not fully understood. This 4‐year Long‐Term Agroecosystem Research Integrated Common Experiment project evaluated the effect of interseeding cereal rye (Secale cereale) into corn for grazing after corn grain harvest on corn grain yield and late‐season grazing. Cereal rye was interseeded into corn in early June. After corn grain harvest, six paddocks at each location were randomly allotted to grazed (GRAZ) or not grazed (NG). The GRAZ paddocks were grazed with beef cattle in late autumn and again in early spring if regrowth allowed. Paddocks were flown with an unmanned aerial system (UAS) to characterize spatial forage yield and quality. Cereal rye provided an additional 20–30 grazing days in the autumn for 24 beef cows on 4.8 ha. Early spring growth shows potential to provide even greater forage yields than autumn, but growth is less dependable. Corn grain yields did not decrease except in 2019 (dry year) when yields were 40% lower. There were no significant differences in soil health indicators between GRAZ and NG paddocks. The UAS shows promise as a tool for monitoring forage yield and quality and optimizing grazing management.

Soils contribute 15%–75% of total atmospheric nitrogen oxide (NO_x) emissions in agricultural regions during the growing season. However, the impacts of cropland fertilizer management on spatially heterogeneous, temporally episodic NO_x emission patterns are highly uncertain. We examine the effects of liquid slurry dairy manure application practices on soil NO_x emissions in rainfed, corn‐soybean rotations during spring 2016 and 2017. Daily soil NO_x emissions and weekly soil inorganic N measurements were performed in a randomized split–split plot design for 1–4 weeks following manure applications. NO_x emissions and soil N with shallow‐disk injection and chisel‐disk manure incorporation methods were compared with unincorporated broadcast practices. Injected manure and chisel‐disk incorporation exhibited two–four times larger mean NO_x emissions than those with unincorporated broadcast manure. Larger soil NO_x emissions with manure incorporation practices were driven by the predominance of nitrification in these treatments with evidence of soil nitrate production. Soil NO_x emission differences between treatments were detectable across order of magnitude changes in daily NO_x emissions during two growing seasons. Larger soil NO_x emissions associated with manure incorporation practices compared with unincorporated broadcast practices occur alongside larger N₂O and smaller NH₃ emissions, highlighting important air quality and climate impact tradeoffs for cropland manure fertilizer management choices.

The specialization and intensification of agriculture have produced incredible gains in productivity, quality, and availability of agricultural commodities but have resulted in the separation of crop and animal production. A by‐product of this separation has been the accumulation of manure regions where animal production is concentrated. Enter the “manureshed,” an organizing framework for integrating animal and crop production where budgeting of manure nutrients is used to strategically guide their recycling and reuse in agricultural production systems where manure resources are of highest value. To move beyond regional nutrient balance analyses into the transformational realm required to mitigate “wicked” manure problems, manureshed management requires recognition of the challenges to systematically reorganizing resource flows. In better integrating crop and livestock systems, manureshed management must account for the unique nature of managing manure nutrients within individual livestock industries, anticipate trade‐offs in substituting manure for commercial fertilizer, promote technologies to refine manure, and engage extensive social networks across scales that range from the farmgate to nation and beyond.

The manureshed represents cropland needed to safely assimilate manure nutrients from an animal feeding operation. Dairy manuresheds can be contained on‐farm but may need to involve additional farms that can assimilate excess nutrients. We present case studies reviewing challenges and opportunities to manureshed management in four major dairy‐producing states using available information on local manuresheds. Additionally, geographic information system software was used with data from regulated Minnesota dairies to assess cropland assimilative capacities and transport needs surrounding large dairies. Manureshed requirements vary across regions, but increased import of feed and soil phosphorus accumulation constrain on‐farm manure utilization across the United States. In Minnesota, a growing proportion of Jersey cattle and differences in continuous corn (Zea mays L.) vs. corn–alfafa (Medicago sativa L.) rotations contribute to the amount of land needed to absorb dairy manure nutrients. Farm‐gate budgets reveal that N‐based manuresheds can be contained within Idaho dairies, but P‐based manuresheds extend beyond the farm. In New Mexico, relocation of surplus manure nutrients off the farm is common via informal networks, but incentives to strengthen these networks could ensure sustainable manureshed management. Evaluation of manureshed requirements in Pennsylvania is often complicated by the need for additional nutrient management planning and greater understanding of nutrient balances on the preponderance of small dairies. Nutrient imbalances with highly concentrated dairy production often lead to the need for manure transport off‐farm. However, advances in herd and cropland management offer opportunities to improve on‐farm nutrient efficiencies, and emerging networks and technologies promise to facilitate manure export when needed.

The potential of conservation practices to maintain soil organic C (SOC) and reduce climate change impacts on yields is unknown. This study aimed to validate the DayCent model with observed yield data and the CQESTR model with measured SOC in two agroecosystems, and predict the best practices to sustain SOC under projected climate change. Data were from a conventional tillage (CT) wheat ( Triticum aestivum L.)–fallow rotation without N or with 135 kg N ha ^–1 fertilizer, and no‐till (NT) experiments, NT _A (NT _A0 W‐F and NT _A135 W‐F) and NT _B with a wheat–pea ( Pisum sativum L.) cover crop (NT _B0 W‐P and NT _B135 W‐P) in Oregon; and crop rotations with CT and NT silage or grain corn (Zea mays L.)–soybean [Glycine max (L.) Merr.]–alfalfa ( Medicago sativa L.) with or without manure or stover removal or a cover crop in Pennsylvania. Measured and CQESTR‐simulated SOC were significantly ( p <  .0001) correlated ( r = .90). In Oregon, predicted SOC to 60 cm increased under NT _A135 W‐F and NT _B135 W‐P at 0.05 and 0.08 Mg ha ^–1 yr ^–1 under projected climate change, respectively. The NT management under dryland production provided a limited SOC increase. In Pennsylvania, predicted SOC to 1 m decreased at 0.07 Mg ha ^–1 yr ^–1 in corn–soybean under CT or NT with stover removal, but increased by 0.71 Mg ha ^–1 yr ^–1 in dairy forage NT and manure added under climate change. The responses of SOC to climate change were affected by management, biomass type, edaphic properties, local climate, and agroecosystem.