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1. Life cycle greenhouse gas emissions for irrigated corn production in the U.S. great plains

   https://doi.org/10.1016/j.envc.2023.100750  

   Koushki, Raana ; Sharma, Sumit ; Warren, Jason ; Foltz, Mary E. ( December 2023 , Environmental Challenges)

   Agricultural management practices improve crop yields to satisfy food demand of the growing population. However, these activities can have negative consequences, including the release of greenhouse gas (GHG) emissions that contribute to global climate change. To mitigate this global environmental problem, the management practices that contribute the most to system GHG emissions should be identified and targeted to mitigate emissions. Accordingly, we estimated the cradle-to-product GHG emissions of irrigated corn production under various farmer-selected scenarios at an experimental testing field in the semi-arid U.S. Great Plains. We applied a carbon footprint approach to quantify life cycle GHG emissions associated with pre-field (e.g., energy production, fertilizer production) and in-field (e.g., groundwater pumping, fertilizer application) activities within fourteen scenarios in the 2020 Oklahoma Testing Ag Performance Solutions (TAPS) sprinkler corn competition. We determined that 63% of the total GHG emission from corn production was associated with in- field activities and that agricultural soil emissions were the overall driving factor. Soil biochemical processes within agricultural soils were expected to contribute an average of 89 ± 18 g CO2-eq kg− 1 corn of the total 271 ± 46 g CO2-eq kg− 1 corn estimated from these systems. On-site natural gas combustion for agricultural groundwater pumping, pre-field fertilizer production, and pre-field energy production for groundwater pumping were the next most influential parameters on total GHG emissions. Diesel fuel, seed, and herbicide production had insignificant contributions to total GHG emissions from corn production. The model was most sensitive to the modeled GHG emissions from agricultural soil, which had significant uncertainty in the emission factor. Therefore, future efforts should target field measurements to better predict the contribution of direct soil emissions to total GHG emissions, particularly under different managements. In addition, identifying the optimal application rate of irrigation water and fertilizer will help to decrease GHG emissions from groundwater irrigated crops. 

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2. Decreasing, not increasing, leaf area will raise crop yields under global atmospheric change

   https://doi.org/10.1111/gcb.13526  

   Srinivasan, Venkatraman ; Kumar, Praveen ; Long, Stephen P. ( November 2016 , Global Change Biology)

   Without new innovations, present rates of increase in yields of food crops globally are inadequate to meet the projected rising food demand for 2050 and beyond. A prevailing response of crops to rising [CO₂] is an increase in leaf area. This is especially marked in soybean, the world's fourth largest food crop in terms of seed production, and the most important vegetable protein source. Is this increase in leaf area beneficial, with respect to increasing yield, or is it detrimental? It is shown from theory and experiment using open‐air whole‐season elevation of atmospheric [CO₂] that it is detrimental not only under future conditions of elevated [CO₂] but also under today's [CO₂]. A mechanistic biophysical and biochemical model of canopy carbon exchange and microclimate (MLCan) was parameterized for a modernUSMidwest soybean cultivar. Model simulations showed that soybean crops grown under current and elevated (550 [ppm]) [CO₂] overinvest in leaves, and this is predicted to decrease productivity and seed yield 8% and 10%, respectively. This prediction was tested in replicated field trials in which a proportion of emerging leaves was removed prior to expansion, so lowering investment in leaves. The experiment was conducted under open‐air conditions for current and future elevated [CO₂] within the Soybean Free Air Concentration Enrichment facility (SoyFACE) in central Illinois. This treatment resulted in a statistically significant 8% yield increase. This is the first direct proof that a modern crop cultivar produces more leaf than is optimal for yield under today's and future [CO₂] and that reducing leaf area would give higher yields. Breeding or bioengineering for lower leaf area could, therefore, contribute very significantly to meeting future demand for staple food crops given that an 8% yield increase across theUSAalone would amount to 6.5 million metric tons annually.

    

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3. Historical Trends in New Mexico Forage Crop Production in Relation to Climate, Energy, and Rangelands

   https://doi.org/10.3390/su12052051  

   Zaied, Ashraf J. ; Geli, Hatim M. ; Sawalhah, Mohammed N. ; Holechek, Jerry L. ; Cibils, Andres F. ; Gard, Charlotte C. ( March 2020 , Sustainability)

   This study was conducted within the context of providing an improved understanding of New Mexico’s food, energy, water systems (FEWS) and their behavior under variable climate and socioeconomic conditions. The goal of this paper was to characterize the relationships between production and prices of some forage crops (hay, grain sorghum, and corn) that can be used as feed supplements for beef cattle production and the potential impacts from a changing climate (precipitation, temperature) and energy inputs (crude oil production and prices). The analysis was based on 60 years of data (1958–2017) using generalized autoregressive conditional heteroscedasticity models. Hay production showed a declining trend since 2000 and in 2017, it dropped by ~33% compared to that of 2000. Crude oil production (R2 = 0.83) and beef cattle population (R2 = 0.85) were negatively correlated with hay production. A moderate declining trend in mean annual hay prices was also observed. Mean annual range conditions (R2 = 0.60) was negatively correlated with mean annual hay prices, whereas mean annual crude oil prices (R2 = 0.48) showed a positive relationship. Grain sorghum production showed a consistent declining trend since 1971 and in 2017, it dropped by ~91% compared to that of 1971. Mean annual temperature (R2 = 0.58) was negatively correlated with grain sorghum production, while beef cattle population (R2 = 0.61) and range conditions (R2 = 0.51) showed positive linear relationships. Mean annual grain sorghum prices decreased since the peak of 1974 and in 2017, they dropped by ~77% compared to those of 1974. Crude oil prices (R2 = 0.72) and beef cattle population (R2 = 0.73) were positively correlated with mean annual grain sorghum prices. Corn production in 2017 dropped by ~61% compared to the peak that occurred in 1999. Crude oil production (R2 = 0.85) and beef cattle population (R2 = 0.86) were negatively correlated with corn production. Mean annual corn prices showed a declining trend since 1974 and in 2017, they dropped by ~75% compared to those of 1974. Mean annual corn prices were positively correlated with mean annual precipitation (R2 = 0.83) and negatively correlated with crude oil production (R2 = 0.84). These finding can particularly help in developing a more holistic model that integrates FEWS components to explain their response to internal (i.e., management practices) and external (i.e., environmental) stressors. Such holistic modeling can further inform the development and adoption of more sustainable production and resource use practices. 

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4. Food production and resource use of urban farms and gardens: a five-country study

   https://doi.org/10.1007/s13593-022-00859-4  

   Dorr, Erica ; Hawes, Jason K. ; Goldstein, Benjamin ; Fargue-Lelièvre, Agnès ; Fox-Kämper, Runrid ; Specht, Kathrin ; Fedeńczak, Konstancja ; Caputo, Silvio ; Cohen, Nevin ; Poniży, Lidia ; et al ( February 2023 , Agronomy for Sustainable Development)

   There is a lack of data on resources used and food produced at urban farms. This hampers attempts to quantify the environmental impacts of urban agriculture or craft policies for sustainable food production in cities. To address this gap, we used a citizen science approach to collect data from 72 urban agriculture sites, representing three types of spaces (urban farms, collective gardens, individual gardens), in five countries (France, Germany, Poland, United Kingdom, and United States). We answered three key questions about urban agriculture with this unprecedented dataset: (1) What are its land, water, nutrient, and energy demands? (2) How productive is it relative to conventional agriculture and across types of farms? and (3) What are its contributions to local biodiversity? We found that participant farms used dozens of inputs, most of which were organic (e.g., manure for fertilizers). Farms required on average 71.6 L of irrigation water, 5.5 L of compost, and 0.53 m² of land per kilogram of harvested food. Irrigation was lower in individual gardens and higher in sites using drip irrigation. While extremely variable, yields at well-managed urban farms can exceed those of conventional counterparts. Although farm type did not predict yield, our cluster analysis demonstrated that individually managed leisure gardens had lower yields than other farms and gardens. Farms in our sample contributed significantly to local biodiversity, with an average of 20 different crops per farm not including ornamental plants. Aside from clarifying important trends in resource use at urban farms using a robust and open dataset, this study also raises numerous questions about how crop selection and growing practices influence the environmental impacts of growing food in cities. We conclude with a research agenda to tackle these and other pressing questions on resource use at urban farms.

    

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5. Optimizing pollinator conservation and crop yield among perennial bioenergy crops

   https://doi.org/10.1111/gcbb.12826  

   Kemmerling, Lindsey R. ; Griffin, Sean R. ; Haddad, Nick M. ( May 2021 , GCB Bioenergy)

   In order to both combat the decline of biodiversity and produce food, fuel, and fiber for a growing human population, current agricultural landscapes must transition into diversified, multifunctional systems. Perennial cellulosic biofuel crops have potential to meet both of these challenges, acting as multifunctional systems that can enhance biodiversity. What is not well understood, and what we test here, are the tradeoffs among different perennial crops in their performance as biofuels and in biodiversity conservation. Working in an established bioenergy experiment with four native, perennial, cellulosic biofuel crop varieties—ranging from monoculture to diverse restoration planting—we tested the effect of biofuel crop management on flower communities, pollinator communities, and crop yield. The greatest abundance and diversity of pollinators and flowers were in treatments that were successional (unmanaged), followed by restored prairie (seeded mix of native grasses and forbs), switchgrass, and a mix of native grasses. However, biofuel crop yield was approximately the inverse, with native grasses having the highest yield, followed by switchgrass and prairie, then successional treatments. Restored prairie was the optimal biofuel crop when both pollinator conservation and crop yield are valued similarly. We add to mounting evidence that policy is needed to create sustainable markets that value the multifunctionality of perennial biofuel systems in order to achieve greater ecosystem services from agricultural landscapes.

    

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