• Authors:
    • Andersson, K. O.
    • Rawson, A.
    • Murphy, B. W.
    • Simmons, A. T.
    • Badgery, W. B.
    • Lonergan, V. E.
  • Source: AGRICULTURE ECOSYSTEMS & ENVIRONMENT
  • Volume: 196
  • Year: 2014
  • Summary: Changes in land use and management have been proposed as a way to increase soil organic carbon (SOC) in crop and pasture systems. Some of the proposed activities to improve SOC are the introduction of pasture phases in cropping systems, stubble retention, no-till cropping, improved fertilisation, introduction of more productive pasture species and grazing management. There is also growing interest in novel farming systems, such as pasture cropping (intercropping cereal crops with established perennial pastures), which may improve SOC. However, there have been few broad scale surveys to determine whether these land management changes have an impact on commercial farms. In this study, comparisons of land use were established for mixed farming and pasture cropping systems in the slopes region (average annual rainfall: 500-650 mm) and for cropping and pasture in the plains region (average annual rainfall: 300-500 mm) of Central West NSW, Australia. The survey aimed to determine the difference in SOC stocks (MgCha -1) and the composition of three soil organic carbon fractions (particulate - POC, humus - HUM and resistant - ROC). The influences of management actions and pasture composition were also assessed across pasture and cropping land uses. Cropping systems had lower SOC stocks in the soil than pasture systems in each region, but pasture cropping was not different from perennial pasture. Generally, there were larger differences in the POC due to land use and management than the other SOC fractions. Management practices in cropping systems explained greater variability in SOC than in pastures. For cropping systems, higher amounts of P fertiliser were associated with higher SOC, POC and ROC while higher amounts of N fertiliser were associated with lower SOC, POC and ROC. For pastures, the proportion of bare ground was associated with lower SOC and POC. These associations indicate there is an opportunity to increase SOC by converting cropping land to permanent pasture, increasing the frequency of pasture phases, changing crop fertiliser regimes and reducing bare ground in pastures, but further work is needed to verify the causality behind these associations.
  • Authors:
    • Calegari, A.
    • Balota, E. L.
    • Nakatani, A. S.
    • Coyne, M. S.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 197
  • Year: 2014
  • Summary: Soil degradation in Brazil is a concern due to intensive agricultural production. Combining conservation practice, such as no-tillage, with winter cover crops may increase microbial activity and enhance soil quality more than either practice alone. This research evaluated the benefits of long-term (23 years) winter cover crops and reduced tillage on soil microbial quality indicators in an Oxisol from Parana State, Southern Brazil. The winter cover treatments were: fallow, black oat, wheat, radish, blue lupin, and hairy vetch in conventional (plow) or no-tillage management; the summer crop was a soybean/maize rotation. Soil quality parameters included organic C, microbial biomass C and N, total and labile polysaccharide, easily extractable and total glomalin-related soil protein, and enzyme activity. Winter crops increased soil microbial quality parameters compared to fallow in both tillage systems, with greater relative increase in conventional than no-tillage. No-tillage had higher microbial biomass, polysaccharide, glomalin-related soil protein, and soil enzyme activity than conventional tillage. Including legumes in the crop rotation was important for N balance in the soil-plant system, increasing soil organic C content, and enhancing soil quality parameters to a greater extent than grasses or radish. The microbial parameters proved to be more sensitive indicators of soil change than soil organic C. Cultivating winter cover crop with either tillage is a beneficial practice enhancing soil microbial quality and also soil organic C stocks.
  • Authors:
    • Castellano, M. J.
    • Kaspar, T. C.
    • Miguez, F. E.
    • Basche, A. D.
  • Source: JOURNAL OF SOIL AND WATER CONSERVATION
  • Volume: 69
  • Issue: 6
  • Year: 2014
  • Summary: There are many environmental benefits to incorporating cover crops into crop rotations, such as their potential to decrease soil erosion, reduce nitrate (NO3) leaching, and increase soil organic matter. Some of these benefits impact other agroecosystem processes, such as greenhouse gas emissions. In particular, there is not a consensus in the literature regarding the effect of cover crops on nitrous oxide (N2O) emissions. Compared to site-specific studies, meta-analysis can provide a more general investigation into these effects. Twenty-six peer-reviewed articles including 106 observations of cover crop effects on N2O emissions from the soil surface were analyzed according to their response ratio, the natural log of the N2O flux with a cover crop divided by the N2O flux without a cover crop (LRR). Forty percent of the observations had negative LRRs, indicating a cover crop treatment which decreased N2O, while 60% had positive LRRs indicating a cover crop treatment which increased N2O. There was a significant interaction between N rate and the type of cover crop where legumes had higher LRRs at lower N rates than nonlegume species. When cover crop residues were incorporated into the soil, LRRs were significantly higher than those where residue was not incorporated. Geographies with higher total precipitation and variability in precipitation tended to produce higher LRRs. Finally, data points measured during cover crop decomposition had large positive LRRs and were larger than those measured when the cover crop was alive. In contrast, those data points measuring for a full year had LRRs close to zero, indicating that there was a balance between periods when cover crops increased N2O and periods when cover crops decreased emissions. Therefore, N2O measurements over the entire year may be needed to determine the net effect of cover crops on N2O. The data included in this meta-analysis indicate some overarching crop management practices that reduce direct N2O emissions from the soil surface, such as no soil incorporation of residues and use of nonlegume cover crop species. However, our results demonstrate that cover crops do not always reduce direct N2O emissions from the soil surface in the short term and that more work is needed to understand the full global warming potential of cover crop management.
  • Authors:
    • Eisenhauer, D. E.
    • Gilley, J. E.
    • Blanco-Canqui, H.
    • Jasa, P. J.
    • Boldt, A.
  • Source: AGRONOMY JOURNAL
  • Volume: 106
  • Issue: 6
  • Year: 2014
  • Summary: The benefits of grass barriers or hedges for reducing offsite transport of non-point-source water pollutants from croplands are well recognized, but their ancillary benefits on soil properties have received less attention. We studied the 15-yr cumulative effects of narrow and perennial switchgrass ( Panicum virgatum L.) barriers on soil organic C (SOC), total N, particulate organic matter (POM), and associated soil structural properties as compared with the cropped area on an Aksarben silty clay loam (fine, smectitic, mesic Typic Argiudoll) with 5.4% slope in eastern Nebraska. Five switchgrass barriers were established in 1998 at ~38-m intervals parallel to the crop rows in a field under a conventional tillage and no-till grain sorghum [ Sorghum bicolor (L.) Moench]-soybean [ Glycine max (L.) Merr.]-corn ( Zea mays L.) rotation. Compared with the cropped area, switchgrass barriers accumulated about 0.85 Mg ha -1 yr -1 of SOC and 80 kg ha -1 yr -1 of total soil N at the 0 to 15 cm soil depth. Switchgrass barriers also increased coarse POM by 60%. Mean weight diameter of water-stable aggregates increased by 70% at 0 to 15 cm and by 40% at 15 to 60 cm, indicating that switchgrass barriers improved soil aggregation at deeper depths. Large (4.75-8 mm) macroaggregates under switchgrass barriers contained 30% more SOC than those under the cropped area. Switchgrass-induced changes in SOC concentration were positively associated with aggregate stability ( r=0.89***) and porosity ( r=0.47*). Overall, switchgrass barriers integrated with intensively managed agroecosystems can increase the SOC pool and improve soil structural properties.
  • Authors:
    • Giurgiu, R. M.
    • Moraru, P. I.
    • Pop, A. I.
    • Bogdan, I.
    • Rusu, T.
    • Duda, B. M.
    • Coste, C. L.
  • Source: Research Journal of Agricultural Science
  • Volume: 46
  • Issue: 1
  • Year: 2014
  • Summary: This paper focuses on conservative agriculture, determined as minimal soil tillage, no tillage and enduring soil cover (mulch) together with rational rotations, as to achieve a more sustainable cultivation system for the future, in the context of the global warming and the permanent increase of population. Both farming and tillage play important roles in the agricultural systems. The conservative tillage systems in agriculture appeared in the U.S. and have developed in different ways, adapted to climatic zones and are considered unconventional or for soil conservation systems. Our research shows an improvement on conservative tillage, where no tillage, mulch and rotations significantly improve soil properties and other biotic factors also reducing the CO 2 emissions. Advantages of conservative tillage systems are represented by improving soil physics and excellent control of soil erosion, accumulation and water retention in the soil, reduced labor and fuel costs and in some cases even increased productivity. In the conservative tillage systems, land must be covered with plant debris at a rate of 15-30%, and in minimal tillage system with crop residue mulch, coverage exceeds 30%. In the no tillage system, sowing is done directly in the stubble or on a ground covered with plant debris from the preceding plant, using precision machinery. The paper concludes that a conservative tillage system is a more environmentally friendly and sustainable management system for cultivating crops. Case studies from all over the world show that when using conservative agriculture for most of the crops we get a raise production sustainably and profitably. Advantages in terms of greenhouse gas emissions and their effect on global warming are also taken into consideration. These systems also have a big disadvantage, high consumption of herbicides for weed control. An increased attention for direct seeding requires preventive plant protection characters. Seeds must be treated with insecticide-fungicide and soil requires more herbicide than for the classic systems with plough. The paper concludes that farming and agriculture in the next decade will have to produce more food from less or the same land through more efficient management of natural resources and with less impact on the environment in order to sustain the permanent growing population demands. Promoting and adopting conservative agriculture management systems can help meet this goal.
  • Authors:
    • Sternberg, M.
    • Bonfil, D. J.
    • Lifschitz, D.
    • Eshel, G.
  • Source: AGRICULTURE ECOSYSTEMS & ENVIRONMENT Volume: 195 Pages:
  • Volume: 195
  • Year: 2014
  • Summary: The adoption of no-till (NT) cultivation practices in field crops such as wheat ( Triticum aestivum) may mitigate increasing global concentrations of atmospheric CO 2. Little information is currently available on the effects of rainfed wheat cultivation practices on the carbon exchange in arid regions. The goal of the present study was to quantify the long-term (13 years) effects of tillage and fertilization on soil CO 2 fluxes in wheat fields under arid climatic conditions (230 mm rainfall), and evaluate the carbon turnover. It was hypothesized that adopting a NT practice would improve the carbon exchange in wheat fields under arid conditions. During 2007-2009, four different practices were studied in a Calcic Xerosol in Southern Israel: conventional tillage with fertilization (CT + F), conventional tillage without fertilization (CT), no-till with fertilization (NT + F), and no-till without fertilization (NT). CO 2 output as soil respiration efflux and CO 2 input as aboveground net primary production (ANPP) were calculated. The annual carbon loss as CO 2 efflux was higher under NT vs. CT practices both with fertilization (144.91 vs. 110.87 g C m -2y -1) and without it (136.43 vs. 99.52 g C m -2y -1). Similar trends were obtained for the carbon gain derived from wheat ANPP: 132.16 vs. 88.94 g C m -2y -1 for the fertilized treatments, and 110.9 vs. 75.04 g C m -2y -1 for the unfertilized practices under NT and CT, respectively. Furthermore, the physical soil-sealing layer, commonly found under CT practices due to raindrops' impact on the bare soil, highly affects the soil water regime, and also negatively affects soil gas exchange under CT. Our results clearly support the long-term advantages of adopting NT practices, where plant residues create a protective cover on the soil surface, in rainfed arid regions for all good reasons: better rainwater utilization and soil aeration, enhancing soil organic carbon content, and increasing yields.
  • Authors:
    • Watts, D. B.
    • Wood, C. W.
    • Howe, J. A.
    • Gamble, A. V.
    • Van Santen, E.
  • Source: Soil Science Society of America Journal
  • Volume: 78
  • Issue: 6
  • Year: 2014
  • Summary: A frequently used cropping system in the southeastern Coastal Plain is an annual rotation of cotton (Gossypium hirsutum L.) and peanut (Arachis hypogaea L.) under conventional tillage (CT). The traditional peanut-cotton rotation (TR) often results in erosion and loss of soil organic carbon (SOC). Incorporation of bahiagrass (Paspalum notatum Fluegge) into the peanut- cotton rotation for 2 yr (also called a sod-based rotation or SBR) has been suggested for improving SOC, particularly in conjunction with conservation tillage practices. To determine the effect of the SBR on carbon sequestration, SOC and its isotopic composition were evaluated on established (>10 yr) crop rotation systems. Cropping systems evaluated included (i) TR under CT, (ii) TR under strip tillage (ST), (iii) SBR under CT, (iv) SBR under ST, and (v) SBR under ST with cattle grazing. Total SOC, bahiagrass-derived SOC, and potential C mineralization increased in the top 10 cm of soil, indicating the potential for ST to improve soil fertility in SBR systems. Grazing bahiagrass decreased SOC in the 5 to 10 cm depth, but this effect was not observed for the subsequent peanut crop and did not appear to have a long-term negative effect on SOC storage. The SBR did not show consistent improvements in total SOC compared with the TR. A 3-yr comparison of SOC concentration revealed C increases in SBR and TR systems, indicating that other conservation practices (e.g., winter cover cropping) are the primary contributors to SOC storage for Coastal Plain soils evaluated in this study. Isotopic analysis of mineralized CO2 indicated bahiagrass-derived SOC may be preferred over C3 crop-derived SOC for degradation.
  • Authors:
    • Lal, R.
    • Kadono, A.
    • Nakajima, T.
    • Kumar, S.
    • Fausey, N.
  • Source: JOURNAL OF SOIL AND WATER CONSERVATION
  • Volume: 69
  • Issue: 6
  • Year: 2014
  • Summary: Intensive tillage practices and poorly drained soils of the Midwestern United States are one of the prime reasons for increased greenhouse gas (GHG) fluxes from agriculture. The naturally poorly drained soils prevalent in this region require subsurface drainage for improving aeration and reducing GHG fluxes from soils. However, very little research has been conducted on the combination of tillage and drainage impacts on GHG fluxes from poorly drained soils. Thus, the present study was conducted in central Ohio with specific objective to assess the influences of long-term (18-year) no-tillage (NT) and chisel-till (CT) impacts on carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) fluxes from the soils in plots managed under drained (D) or nondrained (ND) conditions. The experimental site was established on a poorly drained Crosby silt loam soil in 1994 under corn (Zed mays L.)-corn rotation. Measurements of soil CO2, N2 O, and CH4 fluxes were conducted biweekly during 2011 and 2012 using the static chamber technique. In 2011, the annual CO2-C and N2 O-N from NT were 18% and 83%, respectively, lower compared to CT. Similar trends were observed for 2012. Methane fluxes were highly variable in both years.Tillage and drainage influenced seasonal soil GHG emissions; however, differences were not always significant. In general, plots under NT with subsurface drainage produced lower emissions compared to those under CT. Subsurface drainage lowered the emissions compared to those under ND. Results from this study concluded that subsurface drainage in poorly drained soils with long-term NT practice can be beneficial for the environment by emitting lower GHG fluxes compared to tilled soils with no drainage. However, long-term monitoring of these fluxes under diverse cropping systems under poorly drained soils is needed.
  • 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.