• Authors:
    • Huber-Sannwald, E.
    • Anaya, C. A.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 147
  • Year: 2015
  • Summary: Conversion of tropical forests to croplands greatly reduces stock size of soil organic resources. Low-impact agriculture may curtail this loss in soil fertility, and favor long-term agroecosystem functioning. In east tropical Mexico, indigenous smallholders have been managing sugarcane plots without burning, fertilizing, tillaging, and removal of crop residues for the last 70 years. This study examined the long-term effects of such low-input sugarcane agriculture on soil aggregate structure and soil organic carbon (SOC) and soil nitrogen (N) stocks along a 50-year chronosequence of cultivation including differently aged sugarcane plots and tropical forests as a reference site. Soils were physically fractioned in four aggregate size classes and in four soil organic matter (SOM) fractions and changes in C concentrations and C/N ratios of these fractions were assessed. Long-term cultivation did not alter soil aggregate structure, or litter C content; however it reduced significantly litter N content in sugarcane compared to forest plots. After 20 years of cultivation, SOC and soil N stocks dropped by 25% at 0-10. cm soil depth compared to current C stocks in forest soils. After 50 years of cultivation, pooled over 0-20. cm, SOC stocks were similar in sugarcane and forest plots, while soil N stocks remained 12-19% lower in sugarcane than in forest plots. The mineral-associated organic C fraction remained unaffected by land use change. Forest conversion to sugarcane, depleted the free light particulate organic matter (POM) C fraction at 0-10. cm depth. Forest intra-aggregate POM C concentration declined after 20 years of cultivation and then recovered after 50 years of cultivation at 0-10. cm depth. This study demonstrates that traditional sugarcane cropping may be a long-term sustainable alternative to sequester SOC, while maintaining moderate soil N fertility levels without trading off on sugarcane production.
  • Authors:
    • McCorkell, B.
    • McHenry, M.
    • Hulugalle, N.
    • Kristiansen, P.
    • Bajgai, Y.
  • Source: NUTRIENT CYCLING IN AGROECOSYSTEMS
  • Volume: 101
  • Issue: 1
  • Year: 2015
  • Summary: Despite scant crop residue input, tillage to control weeds in vegetable systems reduces soil organic carbon (SOC) levels. We hypothesized that vegetable production systems could be made more resistant to the negative effects of tillage on SOC by including a high-residue crop in rotation. Effect of sweet corn (Zea mays L. var. rugosa) residue incorporation in a corn-cabbage (Brassica oleracea L.) rotation in two soil management systems (SMS) (organic or conventional) in two soil types [a Chromosol (Alfisol) and a Vertosol (Vertisol)] on SOC and microbial biomass C (MBC) levels was tested for 2 years. Confounded factors (weed management and fertilisers) in the field experiment were separated in a multi-factorial laboratory experiment. In the field, total organic C (TOC) concentration was increased by 6.5 % in the 0-0.1 m depth by incorporating residue; however SMS exhibited inconsistent results. Organic fertilisers increased TOC whilst simulated tillage decreased it in laboratory. Soil MBC data showed that the biological fertility of soil can be improved by incorporating residues or by combining residue with organic fertiliser. In field residue incorporation in soil increased TOC, but organic fertilisers behaved inconsistently. However, in a laboratory microcosm, both residue and organic fertilisers individually mitigated tillage-induced loss of TOC.
  • Authors:
    • Piccolo, M. D. C.
    • Vieira, F. C. B.
    • Zanatta, J. A.
    • Gomes, J.
    • Bayer, C.
    • Dieckow, J.
    • Six, J.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 146
  • Issue: Pt. B
  • Year: 2015
  • Summary: Soil nitrous oxide (N2O) emissions are affected by management practices, but little information is available on the interactive effects of tillage, cropping systems and N sources in tropical and subtropical soils. In an 18-yr old experiment located in a subtropical Acrisol of Southern Brazil we conducted a sequence of two trials. The 1-year trial (October 2003-2004) was set to evaluate the long-term effects of tillage [CT: conventional; and NT: no-tillage] and cropping systems [O/M: black oat (Avena strigosa Schreb.)/maize (Zea mays L.); and V/M: vetch (Vicia sativa L.)/maize] on soil N2O emissions, either in the post-management period (45 days after desiccation and knife-rolling of winter cover crops) or in the whole year. The second and short-term trial (October-November 2004) was carried out to compare the impact of N sources [urea (mineral) and legume-residue of vetch (biologically fixed), both at 180kgNha-1] on soil N2O emissions during 53 days after cover-crop management. Air sampling was carried out by static chambers and N2O analysis by gas chromatography. In the 45-day post-management period of the 1-year trial, soil N2O emissions were practically not affected by tillage systems, but increased 4 times due to vetch residues (average of 0.40±0.08kgNha-1 in V/M versus 0.10±0.05kgNha-1 in O/M) and related with soil contents of NO3 --N, NH4 +-N, and dissolved organic C (DOC). Over the whole year, soil N2O emissions under CT were similar for grass- and legume-based cropping systems and averaged 0.43±0.17kgNha-1, while NT exacerbated N2O emissions in the legume-based cropping system (0.80±0.07kgNha-1 in V/M versus -0.07±0.06kgNha-1 in O/M). Maize yield was not affected by tillage, but increased from 2.32Mgha-1 in O/M to 4.44Mgha-1 in V/M. Yield-scaled N2O emissions varied from -33g N2O-NMg-1 grain in NT O/M to 179g N2O-NMg-1 grain in NT V/M, and were intermediate in CT soil (106 and 156g N2O-NMg-1grain in V/M and O/M cropping systems, respectively). In the short-term trial, the N2O emitted in excess relative to the control treatment (O/M without N fertilizer) was at least 3 times greater with urea-N (0.44% of applied N) than with legume-residue-Nsource (0.13% of applied N). Yield-scaled N2O emission after vetch residues management (67gNMg-1 grain) was half of that after urea-N application (152gNMg-1 grain). Partially supplying the maize N requirements with winter legume cover-crops may be a feasible strategy to mitigate soil N2O emissions in the subtropical conservation agriculture.
  • Authors:
    • Freebairn, D. M.
    • Dalal, R. C.
    • Seymour, N. P.
    • Bell, M. J.
    • Moody, P. W.
    • Dang, Y. P.
    • Walker, S. R.
  • Source: Soil and Tillage Research
  • Year: 2015
  • Summary: In semi-arid sub-tropical areas, a number of studies concerning no-till (NT) farming systems have demonstrated advantages in economic, environmental and soil quality aspects over conventional tillage (CT). However, adoption of continuous NT has contributed to the build-up of herbicide resistant weed populations, increased incidence of soil- and stubble-borne diseases, and stratification of nutrients and organic carbon near the soil surface. Some farmers often resort to an occasional strategic tillage (ST) to manage these problems of NT systems. However, farmers who practice strict NT systems are concerned that even one-time tillage may undo positive soil condition benefits of NT farming systems. We reviewed the pros and cons of the use of occasional ST in NT farming systems. Impacts of occasional ST on agronomy, soil and environment are site-specific and depend on many interacting soil, climatic and management conditions. Most studies conducted in North America and Europe suggest that introducing occasional ST in continuous NT farming systems could improve productivity and profitability in the short term; however in the long-term, the impact is negligible or may be negative. The short term impacts immediately following occasional ST on soil and environment include reduced protective cover, soil loss by erosion, increased runoff, loss of C and water, and reduced microbial activity with little or no detrimental impact in the long-term. A potential negative effect immediately following ST would be reduced plant available water which may result in unreliability of crop sowing in variable seasons. The occurrence of rainfall between the ST and sowing or immediately after the sowing is necessary to replenish soil water lost from the seed zone. Timing of ST is likely to be critical and must be balanced with optimising soil water prior to seeding. The impact of occasional ST varies with the tillage implement used; for example, inversion tillage using mouldboard tillage results in greater impacts as compared to chisel or disc. Opportunities for future research on occasional ST with the most commonly used implements such as tine and/or disc in Australia's northern grains-growing region are presented in the context of agronomy, soil and the environment.
  • Authors:
    • Zhang, Q.
    • Hu, C.
    • Ren, T.
    • Du, Z.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 146
  • Issue: Pt. A
  • Year: 2015
  • Summary: Physical protection by soil aggregates is critical for building soil organic carbon (SOC) stock. The objective of this study was to identify SOC sequestrated in the microaggregate holding within macroaggregte (mM) fraction after shifting tillage systems in the North China Plain. Soil samples from 0-5. cm layer of a 6-yr field experiment (MP. -. R, moldboard plow without residue; MP. +. R, moldboard plow with residue; RT, rotary tillage with residue; NT, no-till with residue) were collected and separated into different water-stable aggregates. The macroaggregate (250-2000. µm) was further isolated into intra-aggregate particulate organic matter (iPOM) fractions by density flotation, dispersion and sieving. The results showed that the SOC concentration of fine iPOM (250f, 53-250. µm) was increased by 23% in RT and 39% in NT compared with MP. +. R, whereas the difference in the coarse iPOM (250c, >250. µm) was not observed. The ratio of 250f-250c (i.e., 250f/250c) followed the order of NT (2.12). ˜. RT (1.94). >. MP. +. R (1.50). ˜. MP. -. R (1.47), indicating the alternative tillage systems decreased the turnover rates of macroaggregates. Adoption of NT and RT improved the mM formation by 36% and 23% and mM associated C concentration by 38% and 31% as relative to MP. +. R system. Additionally, the soil C concentration and storage of the iPOM and silt plus clay fractions located within the microaggregate were higher under NT and RT than that of MP. +. R and MP. -. R systems. Thus applying NT and RT improved mM formation and soil C sequestered inside this fraction. We concluded that adoption of NT and RT enhanced SOC sequestration in the microaggregates of surface soil of the intensive agroecosystem of North China.
  • Authors:
    • Marquez-Garcia, F.
    • Blanco-Roldan, G. L.
    • Veroz-Gonzalez, O.
    • Gonzalez-Sanchez, E. J.
    • Carbonell-Bojollo, R.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 146
  • Issue: Pt. B
  • Year: 2015
  • Summary: The interest in conservation agriculture in Spain is evidenced by practical and institutional aspects. The practical aspect is reflected by the area cultivated under this farming system, 1.28. Mha in perennial crops and 0.57. Mha in arable crops, both for 2013. The period under review was 2009-2013 for arable crops and 2006-2013 for perennial crops. In that period, figures increased 208% for no tillage in arable crops, and 54% for groundcovers in perennial crops. The institutional support is reflected by the financial funding given to conservation agriculture farming practices by some Spanish Regional Governments, primarily through Rural Development Programs, that reached over € 200 million in the 2000-2006 period. The origins of soil conservation practices date back to the 1930s and have evolved in parallel in America and Europe. This parallelism has led to the use of different terminology for similar practices that do not always fall within the scope of conservationist practices. Consistent with the literature, and based on the results of 6 meetings with 144 Spanish experts, this paper aimed at clarifying terms and practices applied under the conditions of Spain, but could be useful for other geographies. This article also proposes definitions to clearly describe the different concepts for experts, advisers, and also for policy makers to accurately allocate funds in the European financial framework 2014-2020.
  • Authors:
    • Corrêa, J. C.
    • Aita, C.
    • Cassol, P. C.
    • Nicoloso, R. D. S.
    • Grave, R. A.
    • Costa, M. D.
    • Fritz, D. D.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 146
  • Issue: Pt. B
  • Year: 2015
  • Summary: Agriculture can be either a source or sink of atmospheric CO2 depending on soil management. The application of swine slurry in conventional tilled soils could enhance soil CO2 emission depleting soil organic C stocks. However, the use of recalcitrant C-rich organic fertilizers in no-till soils can offset soil CO2 emission promoting soil C sequestration. This hypothesis was tested by evaluating short-term CO2-C emissions from a Rhodic Nitisol under contrasting soil disturbance levels (disturbed (DS) and undisturbed soil (US)) top-dressed with mineral or organic fertilizers (urea (UR), raw swine slurry (RS), anaerobically digested swine slurry (ADS), and composted swine slurry (CS)). Soil CO2 emission was evaluated for 64 days using static chambers where gas samples were collected and analysed by photoacoustic infrared spectroscopy. Soil water-filled pore space (WFPS), temperature and meteorological data were concomitantly registered and a first-order exponential decay model was used to assess the decomposition of organic fertilizers and CO2 emissions induced by soil disturbance. Soil CO2-C emission was correlated with soil temperature, while limiting soil aeration impaired CO2-C efflux when WFPS >0.6cm3cm-3. Disturbance increased soil CO2-C efflux (36.3±2.2kg CO2-Cha-1 day-1) in relation to US (33.3±1.6kg CO2-Cha-1 day-1). Extra labile C input through RS amendment induced an increased soil CO2-C efflux for a longer period (t1/2=16.9 and 9.6 days in DS and US treatments, respectively), resulting in higher CO2-C emissions than soil amended with other fertilizers. The recalcitrant C input by ADS and CS had limited effect on soil CO2-C emissions. CS presented a genuine potential for substantial soil organic C accumulation while offsetting increased CO2-C emissions in comparison to RS amended soils.
  • Authors:
    • Leinweber, P.
    • Baum, C.
    • Acksel, A.
    • Jandl, G.
  • Source: Soil and Tillage Research
  • Volume: 148
  • Year: 2015
  • Summary: Assessing the organic C (Corg) sequestration in no-till soils under perennial crops requires molecular-level quality indicators. Therefore, we investigated the quality of soil organic matter (SOM) in the topsoil under Salix viminalis L. and Lolium perenne L. at two test sites in Central Sweden. The willow S. viminalis (clone 78021) was grown in short rotation coppice, and the grass L. perenne in an adjacent meadow for 17 (site Ultuna) and 15 years (site Enköping), respectively. The concentrations of aliphatic lipids, determined by gas chromatography/mass spectrometry (GC/MS), as well as the molecular composition and thermal stability of the bulk SOM, determined by pyrolysis-field ionization mass spectrometry (Py-FIMS), were tested as indicators for the crop-specific SOM quality. Larger Corg concentrations (factor 1.4) in the topsoil (site Ultuna) under S. viminalis than under L. perenne corresponded to higher concentrations of summed aliphatic lipids (factor 1.6), mainly saturated n-alkanoic acids (factor 2.1) and n-alkanols (factor 1.5) in the GC/MS-analyses. Moreover, in the willow stand (site Ultuna) at soil depth of 0-10cm disproportionally higher concentrations of saturated n-alkanoic acids (C17-C36) (factor 2.4) and n-alkanes (C21-C36) (factor 2.6) indicated a preferential sequestration of aliphatic C because the bulk Corg concentrations were only larger by factor 1.4. This crop-specific impact on SOM at soil depth of 0-10cm was proven for both test sites. Furthermore, the Py-FIMS showed larger abundances of thermally stabile alkylaromatics (factor 1.4), and non-peptidic N-containing compounds (factor 1.3) in the S. viminalis plot (site Enköping), which supported a crop-specific Corg-sequestration of these compounds. Thus, in summary, accumulations in extracted long C-chain aliphatic lipids and the thermal stability of some substance classes indicated that the Corg sequestration by no-till may be more distinct in soils under S. viminalis than under L. perenne.
  • Authors:
    • Herrera, F.
    • Rasse, R.
    • Giuliante, A.
    • Donoso, L.
    • Perez, T.
    • Marquina, S.
  • Source: NUTRIENT CYCLING IN AGROECOSYSTEMS
  • Volume: 101
  • Issue: 1
  • Year: 2015
  • 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 (NO (x) ), 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:
    • Dargusch, P.
    • Rochecouste, J. -F
    • Cameron, D.
    • Smith, C.
  • Source: Agricultural Systems
  • Volume: 135
  • Year: 2015
  • Summary: The cropping sector in Australia contributes 2.5% of national greenhouse gas emissions, not accounting for the historical loss of soil carbon. The Australian Government is developing policy initiatives targeted at farmers to encourage changes in management practices that aim to reduce emissions from the agricultural sector. The main policy proposal being developed is a market-based mechanism to pay farmers from an Emissions Reduction Fund using methodologies specified under the Australian Carbon Farming Initiative. The adoption of conservation agriculture practices in the dryland grain sector in Australia shows the potential to achieve emissions reductions in the order of three million tCO2e annually. This paper presents a series of systems models that describe the process of how Australian dryland grain farmers decide to change and adopt conservation agriculture practices. Results indicate that a number of economic and social factors drive the rate of practice change, and change seems to be motivated mostly by the pursuit of productivity benefits rather than environmental benefits. We postulate that it may be more effective for climate policy to directly target the adoption of conservation agriculture practices amongst Australian dryland grain farmers by promoting the crop productivity benefits likely to be achieved by such practices, rather than attempting to develop a market-based mechanism for carbon payments. Under this approach, emissions reduction outcomes and carbon payments would not be the primary driver for changing farming practices, but rather a concurrent benefit.