• Authors:
    • Spokas, K. A.
    • Ippolito, J. A.
    • Lentz, R. D.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 78
  • Issue: 5
  • Year: 2014
  • Summary: Few multiyear field studies have examined the impacts of a one-time biochar application on net N mineralization and greenhouse gas emissions in an irrigated, calcareous soil; yet this use of biochar is hypothesized as a means of sequestering atmospheric CO2 and improving soil quality. We fall-applied four treatments: stockpiled dairy manure (42 Mg ha(-1) dry wt.), hardwood-derived biochar (22.4 Mg ha(-1)), combined biochar and manure, and no amendments (control). Nitrogen fertilizer was applied in all plots and years based on treatment's preseason soil test N and crop requirements and accounting for estimated N mineralized from added manure. From 2009 to 2011, we measured greenhouse gas fluxes using vented chambers, net N mineralization using buried bags, corn (Zea mays L.) yield, and N uptake, and in a succeeding year, root and shoot biomass and biomass C and N concentrations. Both amendments produced persistent soil effects. Manure increased seasonal and 3-yr cumulative net N mineralization, root biomass, and root/shoot ratio 1.6-fold, CO2-C gas flux 1.2-fold, and reduced the soil NH4/NO3 ratio 58% relative to no-manure treatments. When compared with a class comprising all other treatments, biochar-only produced 33% less cumulative net N mineralization, 20% less CO2-C, and 50% less N2O-N gas emissions, and increased the soil NH4/NO3 ratio 1.8-fold, indicating that biochar impaired nitrification and N immobilization processes. The multi-year nature of biochar's influence implies that a long-term driver is involved, possibly related to biochar's enduring porosity and surface chemistry characteristics. While the biochar-only treatment demonstrated a potential to increase corn yields and minimize CO2-C and N2O-N gas emissions in these calcareous soils, biochar also caused decreased corn yields under conditions in which NH4-N dominated the soil inorganic N pool. Combining biochar with manure more effectively utilized the two soil amendments, as it eliminated potential yield reductions caused by biochar and maximized manure net N mineralization potential.
  • Authors:
    • Montanarella, L.
    • Panagos, P.
    • Bampa, F.
    • Lugato, E.
    • Jones, A.
  • Source: GLOBAL CHANGE BIOLOGY
  • Volume: 20
  • Issue: 11
  • Year: 2014
  • Summary: Bottom-up estimates from long-term field experiments and modelling are the most commonly used approaches to estimate the carbon (C) sequestration potential of the agricultural sector. However, when data are required at European level, important margins of uncertainty still exist due to the representativeness of local data at large scale or different assumptions and information utilized for running models. In this context, a pan-European (EU+Serbia, Bosnia and Herzegovina, Montenegro, Albania, Former Yugoslav Republic of Macedonia and Norway) simulation platform with high spatial resolution and harmonized data sets was developed to provide consistent scenarios in support of possible carbon sequestration policies. Using the CENTURY agroecosystem model, six alternative management practices (AMP) scenarios were assessed as alternatives to the business as usual situation (BAU). These consisted of the conversion of arable land to grassland (and vice versa), straw incorporation, reduced tillage, straw incorporation combined with reduced tillage, ley cropping system and cover crops. The conversion into grassland showed the highest soil organic carbon (SOC) sequestration rates, ranging between 0.4 and 0.8 t C ha -1 yr -1, while the opposite extreme scenario (100% of grassland conversion into arable) gave cumulated losses of up to 2 Gt of C by 2100. Among the other practices, ley cropping systems and cover crops gave better performances than straw incorporation and reduced tillage. The allocation of 12 to 28% of the European arable land to different AMP combinations resulted in a potential SOC sequestration of 101-336 Mt CO 2 eq. by 2020 and 549-2141 Mt CO 2 eq. by 2100. Modelled carbon sequestration rates compared with values from an ad hoc meta-analysis confirmed the robustness of these estimates.
  • Authors:
    • Giuliante, A.
    • Donoso, L.
    • Pérez, T.
    • Marquina, S.
    • Rasse, R.
    • Herrera, F.
  • Source: NUTRIENT CYCLING IN AGROECOSYSTEMS
  • Year: 2014
  • Summary: The largest share of Latin American and Caribbean (LAC) anthropogenic greenhouse gases is derived from land use changes as well as forestry and agriculture, representing up to 67 % of the relative contribution from all sources. However, in spite of the rapid expansion of LAC tropical agriculture, little is known about its impact on atmospheric trace gases emissions, such as nitrogen oxides (NOx), nitrous oxide (N2O) and carbon dioxide (CO2), which are produced in soils by microbial processes and also accelerated in tropical climates. This information is crucial for assessing mitigation strategies linked to agricultural practices to satisfy food demands for the region’s future. We measured NO, N2O and CO2 soil emissions along with soil variables from corn fields under tillage (T) and no-tillage (NT) agriculture at two of the largest cereal-producing regions in Venezuela during the crop-growing season. We found statistically significant positive correlations between the logarithms of nitrogen gas emissions and soil inorganic nitrogen concentrations, soil water and clay contents. Average emissions of NO and CO2 were larger in T than NT sites, while N2O fluxes showed the opposite. CO2 emissions from T were 1.6 as much as those found in NT, whereas N2O was 0.5 of that found in NT. These results imply that NT practices more effectively mitigate climate change from these monoculture systems mainly because of CO2 emission reduction. We suggest then that agricultural mitigation actions for tropical monoculture systems should aim for the enhancement of NT management practices along with N fertilization rate reduction to compensate for the larger N2O emissions.
  • Authors:
    • Nafziger, E. D.
    • Lauer, J. G.
    • Herzmann, D.
    • Helmers, M. J.
    • Dick, W. A.
    • Del Grosso, S. J.
    • Abendroth, L. J.
    • Kravchenko, A. N.
    • Anex, R. P., Jr.
    • Necpalova, M.
    • Sawyer, J. E.
    • Scharf, P. C.
    • Strock, J. S.
    • Villamil, M. B.
  • Source: JOURNAL OF SOIL AND WATER CONSERVATION
  • Volume: 69
  • Issue: 6
  • Year: 2014
  • Summary: Variability in soil organic carbon (SOC) results from natural and human processes interacting across time and space, and leads to large variation in the minimum difference in SOC that can be detected with a particular experimental design. Here we report a unique comparison of minimum detectable differences (MDDs) in SOC, and the estimated times required to observe those MDDs across the north central United States, calculated for the two most common SOC experiments: (1) a comparison between two treatments, e.g., moldboard plow (MP) and no-tillage (NT), using a randomized complete block design experiment; and (2) a comparison of changes in SOC over time for a particular treatment, e.g., NT, using a randomized complete block design experiment with time as an additional factor. We estimated the duration of the two experiment types required to achieve MDD through simulation of SOC dynamics. Data for the study came from 13 experimental sites located in Iowa, Illinois, Ohio, Michigan, Wisconsin, Missouri, and Minnesota. Soil organic carbon, bulk density, and texture were measured at four soil depths. Minimum detectable differences were calculated with probability of Type I error of 0.05 and probability of Type II error of 0.15. The MDDs in SOC were highly variable across the region and increased with soil depth. At 0 to 10 cm (0 to 3.9 in) soil depth, MDDs with five replications ranged from 1.04 g C kg(-1) (0.017 oz C lb(-1); 6%) to 7.15 g C kg(-1) (0.114 oz C lb(-1); 31%) for comparison of two treatments; and from 0.46 g C kg(-1) (0.007 oz C lb(-1); 3%) to 3.12 g C kg(-1) (0.050 oz C lb(-1); 13%) for SOC change over time. Large differences were also predicted in the experiment duration required to detect a difference in SOC between MP and NT (from 8 to > 100 years with five replications), or a change in SOC over time under NT management (from 11 to 71 years with five replications). At most locations, the time required to detect a change in SOC under NT was shorter than the time required to detect a difference between MP and NT. Minimum detectable difference and experiment duration decreased with the number of replications and were correlated with SOC variability and soil texture of the experimental sites, i.e., they tended to be lower in fine textured soils. Experiment duration was also reduced by increased crop productivity and the amount of residue left on the soil. The relationships and methods described here enable the design of experiments with high power of detecting differences and changes in SOC and enhance our understanding of how management practices influence SOC storage.
  • Authors:
    • Lal, R.
    • Al-Kaisi, M.
    • Olson, K. R.
    • Lowery, B.
  • Source: JOURNAL OF SOIL AND WATER CONSERVATION
  • Volume: 69
  • Issue: 6
  • Year: 2014
  • Authors:
    • Mcleod, M.
    • Schwenke, G.
    • Wilson, B. R.
    • Cowie, A.
    • Tighe, M.
    • Rabbi, S. M. F.
    • Badgery, W.
    • Baldock, J.
  • Source: AGRICULTURE ECOSYSTEMS & ENVIRONMENT
  • Volume: 197
  • Year: 2014
  • Summary: This project aimed to identify land uses and soil management practices that have significant associations with soil organic carbon (SOC) stocks (0-0.3 m) in New South Wales (NSW), Australia. The work presented in this paper is based on a one-off survey targeting key land uses and management practices of eastern NSW. Because of the nature of the work, the land uses and management combinations surveyed in different soils and climatic conditions were significantly unbalanced, and separately analyzing associations after breaking the dataset into different land uses may lead to significant increases in Type errors. Therefore, redundancy analysis (RDA) was undertaken to explore the association between explanatory variables (i.e., land uses, soil management, soil properties and environmental variables) and the variation in stocks (mass per unit area) of particulate organic carbon (POC), humic organic carbon (HOC) and resistant organic carbon (ROC) across 780 sites in eastern NSW, south eastern Australia. Results indicated that soil properties, land uses, soil management and environmental variables together could explain 52% of total variation in stocks of the SOC fractions. Specifically soil properties and environmental variables explained 42.8%, whereas land uses and management practices together explained 9.2% of the total variation in SOC fractions. A forward selection RDA was also undertaken considering soil properties and environmental variables as covariates to assess the statistical significance of land uses and management practices on stocks of POC, HOC and ROC. We found that pasture had significant positive associations on stocks of carbon fractions. Among the soil properties and environmental variables rainfall, longitude and elevation had a significant positive influence while pH and bulk density had a significantly negative influence on the HOC, POC and ROC stocks. Using a novel multivariate technique, the current work identified the land uses and soil management that had significant impact on carbon stocks in soil after accounting for influences soil properties and environmental variables.
  • Authors:
    • Wuest, S. B.
    • Williams, J. D.
    • Long, D. S.
  • Source: JOURNAL OF SOIL AND WATER CONSERVATION
  • Volume: 69
  • Issue: 6
  • Year: 2014
  • Summary: The winter wheat (Triticum aestivum L.)/summer fallow rotation typically practiced in the intermediate precipitation zone (300 to 450 mm [12 to 18 in]) of the inland Pacific Northwest has proven to be economically stable for producers in this region. However, multiple tillage operations are used to control weeds and retain seed-zone soil moisture, which disturbs the soil and makes it prone to substantial erosion. Alternatives to this conventional disturbance tillage (DT) system include either no-tillage (NT) or minimum tillage (MT) in combination with increasing cropping intensity. The objective of this study was to compare runoff, soil erosion, crop residue, and yield productivity resulting from NT, and DT, or MT. Small collectors and flumes were used to quantify runoff and soil erosion from small drainages and slopes in three different experiments near Pendleton, Oregon. The first experiment included two neighboring drainages:one farmed using DT with a two-year crop rotation over eight years (2001 to 2008) and the other NT with a four-year crop rotation (2001 to 2008). The second experiment comprised a hillslope planted to different crops using NT over eight years (1998 to 2005) and MT over three years (2006 to 2008). The third experiment was situated in a shallow draw in which NT and MT with a four-year (2004 to 2008) crop rotation was compared. Runoff measured in flumes was substantially influenced by tillage method in the order of DT > NT in a ratio of 10:1 at the first site. At the second site, NT produced no runoff compared to 1.6 mm y(-1) (0.06 in yr(-1)) from MT. Soil erosion was found to be DT > NT in a ratio of 5:1 at the first site and 2:1 for the second site. For small collectors the differences were significant:runoff was DT > NT in a ratio of 47:1 for the first site, and MT > NT in a ratio of 2:1 for the third site. Winter wheat yields did not differ significantly among NT, DT, and MT. Broader acceptance of NT cropping systems in the intermediate precipitation zone of this region would substantially decrease soil losses from farm fields and improve downstream water quality.
  • Authors:
    • Barfoot, P.
    • Brookes, G.
  • Source: AGRO FOOD INDUSTRY HI-TECH
  • Volume: 25
  • Issue: 4
  • Year: 2014
  • Summary: This paper summarises the economic and key environmental impacts that crop biotechnology has had on global agriculture. The analysis shows that there have been very significant net economic benefits at the farm level amounting to $18.8 billion in 2012 and $116.6 billion for the seventeen year period 1996-2012 (in nominal terms). These economic gains have been divided roughly 50 percent each to farmers in developed and developing countries. GM technology have also made important contributions to increasing global production levels of the four main crops, having added 122 million tonnes and 230 million tonnes respectively, to the global production of soybeans and maize since the introduction of the technology in the mid-1990s. In terms of key environmental impacts, the adoption of the technology has reduced pesticide spraying by 503 million kg (-8.8 percent) and, as a result, decreased the environmental impact associated with herbicide and insecticide use on these crops (as measured by the indicator the Environmental Impact Quotient (EIQ)) by 18.7 percent. The technology has also facilitated a significant reduction in the release of greenhouse gas emissions from this cropping area, which, in 2012, was equivalent to removing 11.88 million cars from the roads.
  • Authors:
    • Burmester, C. H.
    • Balkcom, K. S.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 2
  • Year: 2014
  • Summary: Alabama wheat ( Triticum aestivum L.) farmers are changing management practices, which include using higher N fertilizer rates and planting wheat with no-tillage or other conservation tillage systems to maximize yields. Experiments were conducted to (i) determine the level of tillage necessary to optimize wheat yields across different regions of Alabama and (ii) determine if N requirements change across tillage systems and regions in Alabama at four locations resulting in 9 site-year comparisons. Each experiment consisted of a split-plot design with tillage as the main plot and 12 N fertilizer treatments as subplots, replicated four times to compare Zadoks' Growth Stage (GS)-30 tiller densities, tiller N concentrations, tiller biomass, GS-31 wheat biomass, biomass N concentration, wheat yields, and grain crude protein. Nitrogen treatments consisted of different rates across fall, GS-30, and GS-31 application times. Tillage systems had no effect on tiller density, tiller N concentration, or tiller biomass, but fall N increased tiller density 15% and tiller biomass 34% across Coastal Plain locations. Non-inversion tillage increased wheat yields 13% on Coastal Plain soils compared to conventional tillage. Fall N increased wheat yields 10%, and N applied at GS-30 improved yields 18% compared to delaying application until GS-31, indicating application of fall N and applying total N by GS-30 was imperative for successful wheat production on Coastal Plain soils. Neither tillage system nor N applications affected wheat production extensively across the Limestone Valley. Non-inversion tillage or no-tillage with current recommended N practices can be successfully used in Alabama wheat production.
  • Authors:
    • Utomo,M.
  • Source: Sustainable Living with Environmental Risks
  • Volume: 9784431548041
  • Year: 2014
  • Summary: Global warming due to greenhouse gas emissions is currently receiving considerable attention worldwide. Agricultural systems contribute up to 20 % of this global warming. However, agriculture can reduce its own emissions while increasing carbon sequestration through use of recommended management practices, such as consernvation tillage (CT). The objective of this paper is to review the role of long-term CT in mitigating greenhouse gas emissions during corn production in rainfed tropical agro-ecosystems. The types of conservation tillage were no-tillage (NT) and minimum tillage (MT). In a long-term plot study, CO2 emission from CT throughout the corn season was consistently lower than that from intensive tillage (IT). The cumulative CO2 emissions of NT, MT, and IT in corn crops were 1.0, 1.5, and 2.0 Mg CO2-C ha-1season-1, respectively. Soil carbon storage at 0-20 cm depth after 23 years of NT cropping was 36.4 Mg C ha-1, or 43 % and 20 % higher than the soil carbon strorage of IT and MT, respectively. Thus, NT had sequestered some 4.4 Mg C ha-1of carbon amounting to carbon sequestration rate of 0.2 Mg C ha-1 year-1. IT, on the other hand, had depleted soil carbon by as much as 6.6 Mg C ha-1, yielding a carbon depletion rate of 0.3 Mg C ha-1 year-1. Assessment of the farmer's corn fields confirmed these findings. CO2 emission from CT corn farming was similar to that of rubber agroforest and lower than IT corn farming. Based on carbon balance analysis, it can be concluded that corn crops in tropical rainfed agro-ecosystems were not in fact net emitters, and that NT was a better net sinker than other tillage methods. © 2014 The Editor(s) (if applicable) and the Author(s). All rights reserved.