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1. Spatial optimization of nutrient recovery from dairy farms to support economically viable load reductions in the Chesapeake Bay Watershed

   https://doi.org/10.1016/j.agsy.2023.103640  

   Femeena, P.V.; Costello, C.; Brennan, R.A. (April 2023, Agricultural Systems)

   CONTEXT: To promote circularity in agricultural systems, the utilization of aquatic vegetation for ecological wastewater treatment is a potential mechanism to capture and upcycle nutrients. Agricultural wastewater is an excellent growing medium for aquatic plants like duckweed, offering opportunities for wastewater treatment and conversion of harvested biomass into bio-based products, including protein-rich livestock feed, which can potentially replace conventional soil-based crops such as alfalfa. OBJECTIVE: We hypothesize that nitrogen (N) and phosphorus (P) loadings to the Chesapeake Bay Watershed (CBW) can be reduced via replacing alfalfa cultivation with manure-grown duckweed by: a) reducing excess manure application on agricultural fields; b) reducing synthetic fertilizer application on alfalfa croplands; and c) decreasing the release of fixed N back into the environment from the decomposition of alfalfa crop residue. METHODS: This study developed an optimization framework to identify locations where alfalfa-to-duckweed replacement could be theoretically employed to minimize N and P loads into the CBW. A relative effectiveness (RE) indicator representing landscape-specific nutrient delivery capacity was included within the framework. Using county-level data on alfalfa yields, cropping area, and nutrient inputs from alfalfa croplands and dairy manure, we identified alfalfa cultivation areas that could be removed and replaced with full or partial duckweed cultivation and land conservation for optimal benefits. 

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2. Production and application of manure nitrogen and phosphorus in the United States since 1860

   https://doi.org/10.5194/essd-13-515-2021  

   Bian, Zihao; Tian, Hanqin; Yang, Qichun; Xu, Rongting; Pan, Shufen; Zhang, Bowen (January 2021, Earth System Science Data)

   null (Ed.)

   Abstract. Livestock manure nitrogen (N) and phosphorus (P) play an importantrole in biogeochemical cycling. Accurate estimation of manure nutrient isimportant for assessing regional nutrient balance, greenhouse gas emission,and water environmental risk. Currently, spatially explicit manure nutrientdatasets over a century-long period are scarce in the United States (US).Here, we developed four datasets of annual animal manure N and P productionand application in the contiguous US at a 30 arcsec resolution overthe period of 1860–2017. The dataset combined multiple data sourcesincluding county-level inventory data as well as high-resolution livestockand crop maps. The total production of manure N and P increased from 1.4 Tg N yr−1 and 0.3 Tg P yr−1 in 1860 to 7.4 Tg N yr−1 and 2.3 Tg P yr−1 in 2017, respectively. The increasing manure nutrient productionwas associated with increased livestock numbers before the 1980s andenhanced livestock weights after the 1980s. The manure application amountwas primarily dominated by production, and its spatial pattern was impactedby the nutrient demand of crops. The intense-application region mainlyenlarged from the Midwest toward the southern US and became moreconcentrated in numerous hot spots after the 1980s. The South Atlantic–Gulf and Mid-Atlantic basins were exposed to high environmental risks due to theenrichment of manure nutrient production and application from the 1970s tothe period of 2000–2017. Our long-term manure N and P datasets providedetailed information for national and regional assessments of nutrientbudgets. Additionally, the datasets can serve as the input data forecosystem and hydrological models to examine biogeochemical cycles interrestrial and aquatic ecosystems. Datasets are available at https://doi.org/10.1594/PANGAEA.919937 (Bian etal., 2020). 

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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. Perennial grass bioenergy cropping systems: Impacts on soil fauna and implications for soil carbon accrual

   https://doi.org/10.1111/gcbb.12903  

   Zahorec, Allison; Reid, Matthew L.; Tiemann, Lisa K.; Landis, Douglas A. (October 2021, GCB Bioenergy)

   ABSTRACT Perennial grass energy crop production is necessary for the successful and sustainable expansion of bioenergy in North America. Numerous environmental advantages are associated with perennial grass cropping systems, including their potential to promote soil carbon accrual. Despite growing research interest in the abiotic and biotic factors driving soil carbon cycling within perennial grass cropping systems, soil fauna remain a critical yet largely unexplored component of these ecosystems. By regulating microbial activity and organic matter decomposition dynamics, soil fauna influence soil carbon stability with potentially significant implications for soil carbon accrual. We begin by reviewing the diverse, predominantly indirect effects of soil fauna on soil carbon dynamics in the context of perennial grass cropping systems. Since the impacts of perennial grass energy crop production on soil fauna will mediate their potential contributions to soil carbon accrual, we then discuss how perennial grass energy crop traits, diversity, and management influence soil fauna community structure and activity. We assert that continued research into the interactions of soil fauna, microbes, and organic matter will be important for advancing our understanding of soil carbon dynamics in perennial grass cropping systems. Furthermore, explicit consideration of soil faunal effects on soil carbon can improve our ability to predict changes in soil carbon following perennial grass cropping system establishment. We conclude by addressing the major knowledge gaps that should be prioritized to better understand and model the complex connections between perennial grass bioenergy systems, soil fauna, and carbon accrual. 

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5. Changing climates, changing lives: Voices of a Brazilian Amazon farming community in a time of climate crisis

   https://doi.org/10.1371/journal.pclm.0000522  

   Monteverde, Corrie; Quandt, Amy; Gilberto_de_Souza_Ribeiro, João; De_Sales, Fernando (November 2024, PLOS Climate)

   Ahmed, Ferdous (Ed.)

   This study examines the lived experiences and adaptation strategies of small-scale farmers in the southwestern Brazilian Amazonian state of Rondônia, amidst escalating climate challenges. Through nine in-depth interviews, it uncovers the impact of unpredictable weather, increased temperatures, and shifting precipitation on agriculture and livelihoods. Participants, ranging from family farmers to agricultural collective members, detail shifts from traditional crop cultivation to more resilient practices like cattle ranching and dairy production. The narratives reveal a deep understanding of local climate volatility and its direct effects on water availability, crop viability, and livestock productivity. Farmers describe adaptation measures including new crop varieties, irrigation systems, and strategic land use to enhance biodiversity and mitigate climate change effects. Despite these adaptations, challenges like water scarcity, high input costs, and the need for technical assistance remain prominent. Farmers emphasize the need for stronger support systems, highlighting community solidarity, governmental aid, and access to sustainable technologies and education as essential for climate adaptation. They call for policies providing equitable resources and support, underscoring the importance of inclusive climate governance that acknowledges the unique vulnerabilities and contributions of Rondônia’s agricultural sector. This research contributes to understanding how climate change reshapes rural Amazonian communities, arguing that ongoing deforestation and climatic changes threaten regional agricultural stability. It advocates for targeted policy interventions to provide technical assistance for sustainable farming and climate adaptation, alongside mechanisms to support fair market pricing. These measures are essential for enhancing the resilience and sustainability of local farming communities amidst climate change. 

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