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Process-based agroecosystem models are powerful tools to assess performance of managed landscapes, but their ability to accurately represent reality is limited by the types of input data they can use. Ensuring these models can represent cropping field heterogeneity and environmental impact is important, especially given the growing interest in using agroecosystem models to quantify ecosystem services from best management practices and land use change. We posited that augmenting process-based agroecosystem models with additional field-specific information such as topography, hydrologic processes, or independent indicators of yield could help limit simulation artifacts that obscure mechanisms driving observed variations. To test this, we augmented the agroecosystem model Agricultural Production Systems Simulator (APSIM) with field-specific topography and satellite imagery in a simulation framework we call Foresite. We used Foresite to optimize APSIM yield predictions to match those created from a machine learning model built on remotely sensed indicators of hydrology and plant productivity. Using these improved subfield yield predictions to guide APSIM optimization, total N O 3 − N loss estimates increased by 39% in maize and 20% in soybeans when summed across all years. In addition, we found a disproportionate total amount of leaching in the lowest yielding field areas vs the highest yielding areas in maize (42% vs 15%) and a similar effect in soybeans (31% vs 20%). Overall, we found that augmenting process-based models with now-common subfield remotely sensed data significantly increased values of predicted nutrient loss from fields, indicating opportunities to improve field-scale agroecosystem simulations, particularly if used to calculate nutrient credits in ecosystem service markets.

Progress on reducing nutrient loss from annual croplands has been hampered by perceived conflicts between short‐term profitability and long‐term stewardship, but these may be overcome through strategic integration of perennial crops. Perennial biomass crops like switchgrass can mitigate nitrate‐nitrogen (NO3‐N) leaching, address bioenergy feedstock targets, and – as a lower‐cost management alternative to annual crops (i.e., corn, soybeans) – may also improve farm profitability. We analyzed publicly available environmental, agronomic, and economic data with two integrated models: a subfield agroecosystem management model, Landscape Environmental Assessment Framework (LEAF), and a process‐based biogeochemical model, DeNitrification‐DeComposition (DNDC). We constructed a factorial combination of profitability and NO3‐N leaching thresholds and simulated targeted switchgrass integration into corn/soybean cropland in the agricultural state of Iowa, USA. For each combination, we modeled (i) area converted to switchgrass, (ii) switchgrass biomass production, and (iii) NO3‐N leaching reduction. We spatially analyzed two scenarios: converting to switchgrass corn/soybean cropland losing >US $ 100 ha−1 and leaching >50 kg ha−1 (‘conservative’ scenario) or losing >US$0 ha−1 and leaching >20 kg ha−1 (‘nutrient reduction’ scenario). Compared to baseline, the ‘conservative’ scenario resulted in 12% of cropland converted to switchgrass, which produced 11 million Mg of biomass and reduced leached NO3‐N 18% statewide. The ‘nutrient reduction’ scenario converted 37% of cropland to switchgrass, producing 34 million Mg biomass and reducing leached NO3‐N 38% statewide. The opportunity to meet joint goals was greatest within watersheds with undulating topography and lower corn/soybean productivity. Our approach bridges the scales at which NO3‐N loss and profitability are usually considered, and is informed by both mechanistic and empirical understanding. Though approximated, our analysis supports development of farm‐level tools that can identify locations where both farm profitability and water quality improvement can be achieved through the strategic integration of perennial vegetation. We modelled the effects of strategic subfield integration of switchgrass into corn/soybean cropland on Nitrate‐Nitrogen (NO3‐N) leaching reduction, using two decision making scenarios. In an exemplary impaired watershed in Iowa, in which 80 % of land is in corn/soybeans, the ‘conservative’ scenario would result in 14.3 % of considered cropland converted to switchgrass with a concomitant NO3‐N leaching reduction of 11.3 %. The ‘nutrient reduction’ scenario would result in 39.7 % of considered cropland converted to switchgrass and reduce NO3‐N leached by 31.4 %.

Within-field spatial variability reduces growers’ return on investment and overall productivity while potentially increasing negative environmental impacts through increased soil erosion, nutrient runoff, and leaching. The hypothesis that integrating energy crops into non-profitable segments of agricultural fields could potentially increase grain yield and biomass feedstock production was tested in this study using a statewide analysis of predominantly corn- and soy-producing counties in Iowa. Basic and rigorous controls on permissible soil and soil-carbon losses were imposed on harvest of crop residues to enhance year-to-year sustainability of crop and residue production. Additional criteria limiting harvesting costs and focus on large-area subfields for biomass production were imposed to reduce the impacts of energy crop integration on grain production. Model simulations were conducted using 4 years (2013–2016) of soil, weather, crop yield, and management practice data on all counties in Iowa. Miscanthus (Miscanthus x giganteus), switchgrass (Panicum virgatum), and crop-residue-based bioenergy feedstock systems were evaluated as biomass. Average energy crop and plant residue harvesting efficiencies were estimated at 50 and 60%, respectively. Because of higher potential yields, average logistics costs for miscanthus-based biomass production were 15 and 23% lower than switchgrass-based and crop residue-based biomass productions, respectively, under basic sustainability controls, and 17 and 26% lower under rigorous sustainability controls. Subfield shape, size, area, and harvest equipment size were the dominant factors influencing harvesting cost and efficiency suggesting that in areas where subfields are predominantly profitable or harvesting efficiencies low, other options such as prairie strips, buffer zones around fields, and riparian areas should be investigated for more profitable biomass production and sustainable farming systems.

Integrated landscape management has emerged in recent years as a methodology to integrate the environmental impacts of various agricultural practices along with yield and profitability in a variety of cropping systems. In this study, the Landscape Environmental Assessment Framework (LEAF), a decision support toolset for use in integrated landscape management and developed at Idaho National Laboratory, was used to evaluate the profitability of grain-producing subfields, to determine the efficacy of sustainably harvesting residual biomass after grain harvest, and to determine the efficacy of integrating bioenergy crops into grain-producing landscapes to enhance farmer profitability. Three bioenergy crops, sorghum, switchgrass, and miscanthus, were integrated into non-profitable subfields in four US counties. The manuscript describes in detail the material and methods used to define crop rotations, land management units and practices, subfield units and productivity, grain profitability, sustainability criteria, energy crop integration, and feedstock cost estimation. With the integration of bioenergy crops, the overall annual biomass production rates in the four counties could be increased by factors ranging from 0.8 to 21, depending on the energy crop and county, over the annual residue biomass production rates. By modeling the harvesting of residual biomass and energy crops using geo-referenced, precision harvesting equipment and optimal harvesting paths on individual subfields, the average logistics costs including harvesting of both residual biomass and energy crops were observed to fall well below US DOE’s 2017 goals for biomass feedstock price of US$84/ton or US$92.6/dry Mg. Miscanthus, grown in counties in Ohio and Kansas, provided the maximum potential, among the three energy crops considered, for increment in biomass production and also posed maximum threat to the grain production. Considerable variability was observed in the harvesting and total costs because of the size, shape, and productivity of individual subfields. It was shown that variability in the harvesting costs could be used to down-select non-profitable farms with low harvesting costs and high residue and bioenergy crop yields and to reduce the negative impacts of bioenergy crop integration into croplands on grain production. The results of the assessment suggest that (1) the potential to produce biomass is considerably enhanced when non-profitable grain-producing subfields are replaced by bioenergy crops and (2) the subfield-scale integrated landscape assessment provides a defensible methodology to directly address individual farmer’s profitability, sustainability, and environmental stewardship.