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Maize (Zea mays L.) stover can be harvested for multiple uses or left in the field to sustain soil organic carbon (SOC), cycle essential plant nutrients, and protect soil health. This 13‐yr field study quantified effects of no (0 Mg ha–1 yr–1), low (1.0–1.4 Mg ha–1 yr–1), moderate (3.5–4.0 Mg ha–1 yr–1), or high rates (4.7–5.4 Mg ha–1 yr–1) of stover harvest from either continuous maize or maize–soybean [Glycine max (L.) Merr.] rotation on grain yield, plant nutrient concentrations, and multiple soil properties at two sites in Iowa. Stover harvest increased plant macro‐ and micro‐nutrient removal, but did not affect average grain yields of either crops. Soil inorganic carbon (IC), SOC, bulk density, pH, and cation exchange capacity (CEC) showed no significant differences due to stover harvest. Plant tissue and soil‐test nutrient concentration effects were also minor and site‐specific. Stover harvest significantly (p <.05) decreased exchangeable K and Ca concentrations by 8.3–23.8% and 0.3–22.5% but overall soil health indicator effects were minimal. Overall, based on crop yields, plant nutrient and soil‐test concentrations, soil health indicators, and carbon sequestration estimates, maize stover harvest can be sustainable provided: (a) grain yields consistently exceed 11 Mg ha–1, (b) stover removal does not exceed 40% of the aboveground biomass (i.e., 3.5–4.0 Mg ha–1 yr–1), and (c) plant nutrients (especially K) are closely monitored. Core Ideas: Thirteen‐year maize stover harvest effects on crop yield, nutrients, and soil health were quantified.Stover harvest increased plant nutrient removal, but crop grain yields were not affected.There was no effect on soil organic carbon, soil inorganic carbon, pH, bulk density, or cation exchange capacity.If maize stover is going to be harvested, it is essential to closely monitor soil‐test K.With good soil management, crop residue harvest can be sustainable. [ABSTRACT FROM AUTHOR]

Harvesting corn (Zea mays L.) stover for use as bioenergy feedstock may provide short‐term economic benefits and perhaps improve grain yield in continuous corn systems, but excessive stover removal may lead to long‐term depletion of soil C stocks. To better quantify the impacts of stover harvest on the soil C balance, we investigated CO2 fluxes under three harvest treatments (none, moderate, and high) in three continuous corn systems: (a) no tillage and no biochar applications, (b) chisel plowing with biochar amendments, and (c) chisel plowing without biochar amendments were quantified. We sampled static chambers 14, 13, and 15 times in 2010, 2011, and 2012, respectively, and the measurements were used to calibrate the Agricultural Production Systems sIMulator model. Although CO2‐C emissions did not differ among the three systems, both moderate (approximately 30%) and high (approximately 60%) stover removal rates reduced simulated CO2‐C emissions by nearly 10% and more than 22%, respectively. Despite these reductions in CO2 flux, the sum of CO2‐C and stover C exceeded CO2‐C losses in those plots without stover removal. This finding suggested soil C depletion was occurring for the soil and crop management practices used, even though depletion was not evident after 3 years. Application of biochar increased soil C levels, suggesting it may be able to offset some C losses. We conclude that for sustainable, highly productive agroecosystems that include stover harvest, all agronomic practices must be optimized to minimize C losses and maintain soil quality. [ABSTRACT FROM AUTHOR]

Corn (Zea mays L.) stover is a global resource used for livestock, fuel, and bioenergy feedstock, but excessive stover removal can decrease soil organic C (SOC) stocks and deteriorate soil health. Many site‐specific stover removal experiments report accrual rates and SOC stock effects, but a quantitative, global synthesis is needed to provide a scientific base for long‐term energy policy decisions. We used 409 data points from 74 stover harvest experiments conducted around the world for a meta‐analysis and meta‐regression to quantify removal rate, tillage, soil texture, and soil sampling depth effects on SOC. Changes were quantified by: (a) comparing final SOC stock differences after at least 3 years with and without stover removal and (b) calculating SOC accrual rates for both treatments. Stover removal generally reduced final SOC stocks by 8% in the upper 0–15 or 0–30 cm, compared to stover retained, irrespective of soil properties and tillage practices. A more sensitive meta‐regression analysis showed that retention increased SOC stocks within the 30–150 cm depth by another 5%. Compared to baseline values, stover retention increased average SOC stocks temporally at a rate of 0.41 Mg C ha−1 year−1 (statistically significant at p < 0.01 when averaged across all soil layers). Although SOC sequestration rates were lower with stover removal, with moderate (<50%) removal they can be positive, thus emphasizing the importance of site‐specific management. Our results also showed that tillage effects on SOC stocks were inconsistent due to the high variability in practices used among the experimental sites. Finally, we conclude that research and technological efforts should continue to be given high priority because of the importance in providing science‐based policy recommendations for long‐term global carbon management. [ABSTRACT FROM AUTHOR]

Crop residue management, provision of animal feed or bedding, and increased income are potential reasons for harvesting corn (Zea mays L.) stover. Reasons for not doing so include the need for crop residue to restore or increase soil organic matter, protect against wind and water erosion, and cycle plant nutrients. Bioenergy market development may increase the number of producers harvesting corn stover. Can farming practice data predict the likelihood for harvesting corn stover at a national scale? Farm operation, technology, and management variables from the 2010 Agricultural Resource Management Survey (ARMS) of U.S. corn growers were compared between operations that removed corn stover and those that did not. Nationwide, stover was removed from approximately 6.3% of all corn operations, indicating stover harvest was not a common practice in 2010. Factors increasing the likelihood for stover harvest included producing feed corn, managing crop residues for pest control, and farmland ownership. Technology and conservation practice adoption rates were similar in both groups. Excessive stover removal can increase soil degradation. Both groups had erosion control adoption rates of ≤10%, which may provide an additional disincentive to harvest stover. Overall, the evaluated variables were similar between producers that did and did not harvest stover. This assessment provides a 2010 national baseline that can be used for future evaluations as bioenergy and bioproduct markets develop. [ABSTRACT FROM AUTHOR]

For the soil and plant analysis community, development and expansion of biofuels will create many opportunities to provide a wide variety of analytical services. Our objective is to explore potential areas where those services could be marketed to support sustainable development of biofuels. One of the first is to provide soil fertility and plant nutrition information for sustainable feedstock production. Chemical, physical, and biological indicators of soil quality should also be monitored and interpreted using tools such as the soil management assessment framework (SMAF) to ensure soil resources can continue to meet global food, feed, and fiber demands as well as the new demands for biofuels. Feedstock sugar profile information will be needed to help manage conversion processes, calculate economic drivers such as the minimum ethanol selling price (MESP), and determine suitability for other bioproducts. There will also be an increasing need to evaluate a variety of coproducts created by corn (Zea mays) milling, soybean (Glycine max Merr.) processing, and the fledgling lignocellulosic conversion processes. For coproducts produced from wet or dry corn milling and dry grind ethanol production, accurate and efficient analysis and digestibility of fiber components [neutral detergent fiber (NDF), acid detergent fiber (ADF), and total dietary fiber (TDF)], amino acids (lysine, trypotophan, and methionine), fatty acids, and minerals (phosphorus and sulfur) will be needed. In addition, a capacity to accurately and rapidly detect contamination by mycotoxins such as aflatoxin, zearalenone, and fumonisisn or the presence of antibiotics such as penicillin or virginiamycin could potentially be important. For the biodiesel industry, methanol concentrations in crude glycerin must be reduced to meet Food and Drug Administration guidelines and quantified to ensure this coproduct is safe for use in livestock feeds. Finally, monitoring for several processes and coproducts associated with pyrolysis, a thermochemical platform for biomass conversion to bio-oils, biochar, and other products will be needed. We conclude that sustainable development of biofuel industries will have many positive benefits for soils, plant, and animal production systems and the analysts who will provide analytical services for monitoring all aspects of the biofuels industry. [ABSTRACT FROM PUBLISHER]

The Midwestern U.S. landscape is one of the most highly altered and intensively managed ecosystems in the country. The predominant crops grown are maize (Zea mays L.) and soybean [Glycine max (L.) Merr]. They are typically grown as monocrops in a simple yearly rotation or with multiple years of maize (2 to 3) followed by a single year of soybean. This system is highly productive because the crops and management systems have been well adapted to the regional growing conditions through substantial public and private investment. Furthermore, markets and supporting infrastructure are highly developed for both crops. As maize and soybean production have intensified, a number of concerns have arisen due to the unintended environmental impacts on the ecosystem. Many areas across the Midwest are experiencing negative impacts on water quality, soil degradation, and increased flood risk due to changes in regional hydrology. The water quality impacts extend even further downstream. We propose the development of an innovative system for growing maize and soybean with perennial groundcover to recover ecosystem services historically provided naturally by predominantly perennial native plant communities. Reincorporating perennial plants into annual cropping systems has the potential of restoring ecosystem services without negatively impacting grain crop production and offers the prospect of increasing grain crop productivity through improving the biological functioning of the system. [ABSTRACT FROM AUTHOR]

Measured field data were used to compare two allocation methods on life cycle greenhouse gas emissions from corn (Zea mays L.) stover production in the Midwest U.S. We used publicly-available crop yield, nitrogen fertilizer, and direct soil nitrous oxide emissions data from the USDA-ARS Resilient Economic Agricultural Practices research program. Field data were aggregated from 9 locations across 26 site-years for 3 stover harvest rates (no removal; moderate removal – 3.1 Mg ha−1; high removal – 7.2 Mg ha−1) and 2 tillage practices (conventional; reduced/no-till). Net carbon uptake by crops was computed from measured plant carbon content. Monte Carlo simulations sampled input distributions to assess variability in farm-to-gate GHG emissions. The base analysis assumed no change in soil organic carbon stocks. In all cases, net CO 2 uptake during crop growth and soil-respired CO 2 dominated system emissions. Emissions were most sensitive to co-product accounting method, with system expansion emissions ∼15% lower than mass allocation. Regardless of accounting method, lowest emissions occurred for a moderate removal rate under reduced/no-till management. The absence of correlations between N fertilization rate and stover removal rate or soil N 2 O emissions in this study challenges the use of such assumptions typically employed in life cycle assessments Storage of all carbon retained on the field as SOC could reduce emissions by an additional 15%. Our results highlight how variability in GHG emissions due to location and weather can overshadow the impact of farm management practices on field-to-farm gate emissions. Image 1 • Two life cycle assessment approaches using field-based data were compared for corn (Zea mays L.) stover-based biofuel. • Greenhouse gas emissions were most sensitive to co-product accounting method. • Emissions were 15% lower using the system expansion method vs. mass allocation. • Site-specific variability in soil emissions and crop yield affected field-to-farm gate emissions. • Regardless of accounting method, lowest emissions occurred with moderate stover removal under reduced/no-till management. [ABSTRACT FROM AUTHOR]

Corn ( Zea mays L.) stover has been identified as an important feedstock for bioenergy and bio-product production. Our objective was to quantify nutrient removal, carbohydrate composition, theoretical ethanol yield (TEY) for various stover fractions. In 2009, 2010, and 2011, whole-plant samples were collected from one field study in South Carolina (SC) and two in Alabama (AL). Soils at the SC site were classified as a Coxville/Rains-Goldboro-Lynchburg association, while those in AL were either Compass or Decatur. Plants were collected from two 1-m row segments, ears were removed and shelled. A portion of the remaining stalks were dried and ground to represent whole-plant stover. The remaining stalks were fractionated into stalk and leaf biomass from below the ear (bottom), stalk and leaf biomass from above the ear (top), cobs, and grain. A fifth sample representing “above-ear” biomass that might be collected mechanically was calculated using the weight ratios of the top and cob fractions. Carbohydrate and nutrient concentrations were estimated using near-infrared spectroscopy (NIRS) and TEY was calculated. The distribution of carbohydrates, nutrients, and TEY varied significantly among the corn stover fraction and research locations. This indicates that site-specific sampling and analysis should be used to optimize bioenergy and bio-product utilization of corn stover. However, at every location, the above-ear stover fractions were most desirable for cellulosic ethanol production. Furthermore, harvesting only above-ear stover fractions would reduce nutrient removal by 24–61% when compared to harvesting all stover biomass. [ABSTRACT FROM AUTHOR]