Long-term no-till and stover retention each decrease the global warming potential of irrigated continuous corn

Over the last 50 years, the most increase in cultivated land area globally has been due to a doubling of irrigated land. Long-term agronomic management impacts on soil organic carbon (SOC) stocks, soil greenhouse gas (GHG) emissions, and global warming potential (GWP) in irrigated systems, however, remain relatively unknown. Here, residue and tillage management effects were quantified by measuring soil nitrous oxide (N2O) and methane (CH4) fluxes and SOC changes (ΔSOC) at a long-term, irrigated continuous corn (Zea mays L.) system in eastern Nebraska, USA. Management treatments began in 2002, and measured treatments included no or high stover removal (0 or 6.8 Mg DM ha-1 yr-1, respectively) under no-till (NT) or conventional disk tillage (CT) with full irrigation (n = 4). Soil N2O and CH4 fluxes were measured for five crop-years (2011 to 2015), and ΔSOC was determined on an equivalent-mass basis to ~30 cm soil depth. Both area- and yield-scaled soil N2O emissions were greater with stover retention compared to removal and for CT compared to NT, with no interaction between stover and tillage practices. Methane comprise

Twelve Years of Stover Removal Increases Soil Erosion Potential without Impacting Yield

Corn (Zea mays L.) stover (non-grain aboveground biomass) in the US Corn Belt is used increasingly for livestock grazing and co-feed and for cellulosic bioenergy production. Continuous stover removal, however, could alter long-term agricultural productivity by affecting soil organic C (SOC) and soil physical properties, indicators of soil fertility and erosion potential. In this study, we showed that 12 consecutive yr of 55% stover removal did not affect mean grain yields at any N fertilizer rate (4.5, 6.3, and 6.0 Mg ha−1 for 60, 120, and 180 kg N ha−1 yr−1, respectively) in a marginally productive, rainfed continuous corn system under no-till (NT). Although SOC increased in the top 30 cm of all soils since 1998 (0.54–0.79 Mg C ha−1 yr−1), stover removal tended to limit SOC gains compared with no removal. Near-surface soils (0–5-cm depth) were more sensitive to stover removal and showed a 41% decrease in particulate organic matter stocks, smaller mean weight diameter of dry soil aggregates, and lower abundance of water-stable soil aggregates compared with soils with no stover removal. Increasing N fertilizer rate mitigated losses in total water-stable aggregates in near-surface soils related to stover removal. Collectively, however, our results indicated soil structure losses in surface soils due to lower C inputs. Despite no effect on crop yields and overall SOC gains with time using NT management, annually removing stover for 12 yr resulted in a higher risk of wind and water erosion at this NT continuous corn site in the western Corn Belt

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Removal of cattle manure constituents in runoff from no-till cropland as affected by setback distance

Vegetative filter strips located at the bottom of a hillslope have been shown to substantially reduce nutrients and sediment in runoff. Cropland areas could serve a similar function. However, little scientifically derived information is available to help identify the setback distances required to effectively reduce the transport of contaminants in runoff. The objective of this study was to determine the effects of setback distance and runoff rate on the concentrations and mass transport rates of selected constituents following land application of beef cattle manure to a no-till cropland area. The study site had a residue cover of 8.84 Mg ha-1 and a slope gradient of 6.2%. The 20 plots examined during the investigation were 3.7 m across the slope by 4.9, 7.9, 11.0, 17.1, or 23.2 m long. An initial set of rainfall simulation tests were completed to determine background concentrations and mass transport rates of selected constituents. Cattle manure was then applied to the upper 4.9 m of each plot, and additional rainfall simulation tests were conducted. A first-order exponential decay function was used to estimate the effects of setback distance on the concentrations and mass transport rates in runoff. A setback distance of 12.2 m effectively reduced the concentrations of DP, TP, NH4-N, boron, calcium, magnesium, potassium, and sulfate and the mass transport rates of DP, TP, NH4-N, boron, and potassium to background values similar to those measured on the no-manure treatment. Runoff rate was an important variable influencing each the measured constituents, with mass transport rates increasing as runoff rate increased

Long-Term Corn and Soybean Response to Crop Rotation and Tillage

Long-term experiments are essential to understand how crop rotation and tillage practices affect corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] production and its resiliency to variable weather conditions. A 28-yr rainfed experiment was conducted in Nebraska to evaluate continuous corn (CC), the corn phase of corn–soybean rotation (CS), continuous soybean (SS), and the soybean phase of corn–soybean rotation (SC), and tillage system (chisel [CH], tandem disk [DK], moldboard plow [MP], no-till [NT], ridge-tillage [RT], and subsoil tillage [ST]) on grain yield and yield stability. In 19 of 28 yr, CS yields were greater than CC, although the corn grain yield advantage in CS decreased as CC yield increased. Rotated soybean (SC) grain yield was greater than SS in 67% of cropping years, and similar in the remaining 33%. Stability analysis showed that all crop rotation and tillage combinations, except CH for soybean, resulted in stable grain yields across a range of seasonal weather patterns. Corn grain yields were affected by tillage in 29% of the years, while NT soybean resulted in consistently high and stable grain yields following an initial 11-yr lag period. We conclude that crop rotation has a greater impact on corn and soybean production than tillage in the western Corn Belt, although nearly all combinations can produce stable yields if well managed

Long-term no-till and stover retention each decrease the global warming potential of irrigated continuous corn

Over the last 50 years, the most increase in cultivated land area globally has been due to a doubling of irrigated land. Long-term agronomic management impacts on soil organic carbon (SOC) stocks, soil greenhouse gas (GHG) emissions, and global warming potential (GWP) in irrigated systems, however, remain relatively unknown. Here, residue and tillage management effects were quantified by measuring soil nitrous oxide (N2O) and methane (CH4) fluxes and SOC changes (ΔSOC) at a long-term, irrigated continuous corn (Zea mays L.) system in eastern Nebraska, USA. Management treatments began in 2002, and measured treatments included no or high stover removal (0 or 6.8 Mg DM ha-1 yr-1, respectively) under no-till (NT) or conventional disk tillage (CT) with full irrigation (n = 4). Soil N2O and CH4 fluxes were measured for five crop-years (2011 to 2015), and ΔSOC was determined on an equivalent-mass basis to ~30 cm soil depth. Both area- and yield-scaled soil N2O emissions were greater with stover retention compared to removal and for CT compared to NT, with no interaction between stover and tillage practices. Methane comprise

Winter oilseed production for biofuel in the U.S. Corn Belt: Opportunities and limitations

Interest from the U.S. commercial aviation industry and commitments established by the U.S. Navy and Air Force to use renewable fuels has spurred interest in identifying and developing crops for renewable aviation fuel. Concern regarding greenhouse gas emissions associated with land-use change and shifting land grown for food to feedstock production for fuel has encouraged the concept of intensifying current prominent cropping systems through various double cropping strategies. Camelina (Camelina sativa L.) and field pennycress (Thlaspi arvense L.) are two winter oilseed crops that could potentially be integrated into the corn (Zea mays L.)-soybean [(Glycine max (L.) Merr.] cropping system, which is the prominent cropping system in the U.S. Corn Belt. In addition to providing a feedstock for renewable aviation fuel production, integrating these crops into corn-soybean cropping systems could also potentially provide a range of ecosystem services. Some of these include soil protection from wind and water erosion, soil carbon sequestration, water quality improvement through nitrate reduction, and a food source for pollinators. However, integration of these crops into corn-soybean cropping systems also carries possible limitations, such as potential yield reductions of the subsequent soybean crop. This review identifies and discusses some of the key benefits and constraints of integrating camelina or field pennycress into corn-soybean cropping systems and identifies generalized areas for potential adoption in the U.S. Corn Belt

Twelve Years of Stover Removal Increases Soil Erosion Potential without Impacting Yield

Corn (Zea mays L.) stover (non-grain aboveground biomass) in the US Corn Belt is used increasingly for livestock grazing and co-feed and for cellulosic bioenergy production. Continuous stover removal, however, could alter long-term agricultural productivity by affecting soil organic C (SOC) and soil physical properties, indicators of soil fertility and erosion potential. In this study, we showed that 12 consecutive yr of 55% stover removal did not affect mean grain yields at any N fertilizer rate (4.5, 6.3, and 6.0 Mg ha−1 for 60, 120, and 180 kg N ha−1 yr−1, respectively) in a marginally productive, rainfed continuous corn system under no-till (NT). Although SOC increased in the top 30 cm of all soils since 1998 (0.54–0.79 Mg C ha−1 yr−1), stover removal tended to limit SOC gains compared with no removal. Near-surface soils (0–5-cm depth) were more sensitive to stover removal and showed a 41% decrease in particulate organic matter stocks, smaller mean weight diameter of dry soil aggregates, and lower abundance of water-stable soil aggregates compared with soils with no stover removal. Increasing N fertilizer rate mitigated losses in total water-stable aggregates in near-surface soils related to stover removal. Collectively, however, our results indicated soil structure losses in surface soils due to lower C inputs. Despite no effect on crop yields and overall SOC gains with time using NT management, annually removing stover for 12 yr resulted in a higher risk of wind and water erosion at this NT continuous corn site in the western Corn Belt

Long-term nitrogen and tillage effects on soil physical properties under continuous grain sorghum

Citation: Presley, DeAnn, Aaron Sindelar, Meghan Buckley, and David Mengel. "Long-Term Nitrogen and Tillage Effects on Soil Physical Properties under Continuous Grain Sorghum." Agronomy Journal 104.3 (2012): 749-55. https://doi.org/10.2134/agronj2011.0311Grain sorghum [Sorghum bicolor (L.) Moench] is an important grain crop grown in both highly productive and marginal areas in the central Great Plains because of the crop’s ability to utilize the erratic precipitation observed in this region. More effective capture and storage of this limited rainfall is needed to improve the productivity and profitability of dryland agriculture. The objective of this study was to determine the effects of long-term tillage and nitrogen (N) fertilization on soil physical and hydraulic properties after long-term continuous grain sorghum production. Variables included conventional tillage (CT) and no-till (NT) and four rates of N fertilizer. Selected soil quality indicators included soil organic carbon (SOC), bulk density (BD), wet aggregate stability (WAS), and ponded infiltration. No-till accumulated more SOC in the surface 0-5 cm, and was less dense at all depths than CT. When tillage was compared across all N rates, NT contained 30% greater SOC than CT at the 0-5 cm. Mean weight diameter (MWD) was larger with increasing N fertilization and eliminating tillage. Ponded infiltration rates were greatest for the high N fertilization rate under NT, and lowest for the 0 Kg N haˉ¹ rate under CT. In this long-term grain sorghum system, increasing N fertilization rate and NT both positively affected soil physical properties. These improvements in hydraulic properties will aid in more effectively capturing unpredictable precipitation, and further underscore the utility of NT management practices for the central Great Plains region