• Authors:
    • Alakukku, L.
    • Regina, K.
    • Sheehy, J.
    • Six, J.
  • Source: Soil and Tillage Research
  • Volume: 150
  • Year: 2015
  • Summary: Minimum tillage practices have been shown to enhance soil aggregation and soil organic carbon (SOC) stabilization. Carbon turnover rate slows down when soil aggregation increases and SOC is protected within stable microaggregates (53-250. µm). However, this has not been investigated in boreal soils. Therefore, the objective of this study was to quantify the long-term effects of no-till (NT) and reduced tillage (RT) on SOC stabilization in four soils typical for the boreal region. Distribution of SOC in different soil fractions in a 0-20. cm soil layer was analyzed by wet sieving and further isolation of microaggregates (mM) from large (>2000. µm, LM) and small (250-2000. µm, sM) macroaggregates. Aggregate size decreased in the order of NT. >. RT. >. CT at all study sites. In addition to increased mean weight diameter (MWD) under NT, a general trend of redistribution of SOC into these formed macroaggregates was found at all study sites, i.e., the LM fraction gained SOC. However SOC was lost in other fractions under NT compared to CT at some sites and none of the sites showed any significant changes in bulk soil SOC content under NT or RT. Also our hypothesis that there would be more SOC incorporated in mM fraction in NT and RT compared to CT was corroborated only at site 4 under NT. Thus, although the potential to accumulate SOC under NT or RT compared to CT seems to be limited in boreal agroecosystems, the redistribution of SOC to the more stable conditions within the aggregates indicates positive impacts of no-till practice.
  • Authors:
    • Kaneko, N.
    • Komatsuzaki, M.
    • Yagioka, A.
    • Ueno, H.
  • Source: AGRICULTURE ECOSYSTEMS & ENVIRONMENT
  • Volume: 200
  • Year: 2015
  • Summary: Abandoned agricultural land could potentially accumulate soil organic carbon (SOC) when it is no longer used for cultivation and is allowed to revert to natural vegetation. In Japan, no tillage with weed mulching will be adopted in marginal farmland as a new organic farming system because this system minimizes the disturbance of the soil ecosystem and reduces the cost for crop production. The present study aimed to compare the effects of two organic farming systems, namely no-tillage with weed cover mulching and conventional tillage (CT), and two organic fertilizer application modes, namely no fertilizer (N-) and organic fertilizer (N+; 50kgNha-1 during 2010 and 2011 and 80kgNha-1 during 2012) on greenhouse gas (GHG) fluxes, soil carbon sequestration, net global warming potential (GWP), and nitrate leaching. Pumpkin (Cucurbita spp.) was cultivated as the main crop in 2010 and 2011, whereas mixed cropping of okra (Abelmoschus esculentus L.), bell pepper (Capsicum annuum L.), and eggplant (Solanum melongena L.) was implemented in 2012. Tillage management increased CH4 uptake immediately after the tillage; however, the effects did not continue in the long term. On the contrary, NTW increased CH4 uptake, and the soil carbon content at the soil surface linearly increased every year after conversion to NTW indicating that improving soil physics by continuing NTW contributed to enhanced CH4 uptake. N2O emissions in NTW were higher only immediately after a weed mowing; however, NTW did not increase the annual N2O emission. In addition, the difference between initial and final SOC (dSOC) was greater in NTW than in CT, which significantly decreased net GWP in NTW in comparison with CT. Nitrate leaching was 48.6% and 47.3% lower in NTW than in CT at soil depths of 30-60 and 60-90cm, respectively. These results show that no-tillage with weed cover mulching contributed to conserve the regional and global environment by reducing nitrate leaching and net GWP from the agro-ecosystem by increasing the annual CH4 uptake and soil carbon sequestration. This system will be adopted for abandoned agricultural land because it reduces net GWP shortly after conversion to this management.
  • Authors:
    • Ren, T.
    • Zhou, T.
    • Gao, W.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 79
  • Issue: 2
  • Year: 2015
  • Summary: The quantity and stability of soil organic matter (SOM) associated with soil aggregates are affected by tillage management, which can be characterized potentially using the technique of thermal analysis. In this study, we evaluated the concentration and thermal stability of SOM occulted with various aggregate classes under no-tillage (NT) and moldboard plow (MP) treatments using thermogravimetry (TG) and differential scanning calorimetry (DSC). Soil samples were collected 10 yr after tillage experiment was started. The results showed that conversion from MP to NT significantly increased SOM concentration and the proportion of large macro-aggregates (>2 mm) in the 0- to 5-cm soil layer. For all aggregate classes the derivatives of thermogravimetry curves (DTG) had three weight loss peaks near 100, 350, and 500°C, and one endothermic peak and three exothermic peaks in the DSC curves. No differences in ignition temperature, peak position, and ending temperature of SOM combustion were observed between tillage treatments and among the soil layers. For both tillage systems, the proportion of thermal labile SOM (weight loss in 200-400°C accounting for that in 200-550°C, Exo1/Exotot) and energy densities (ED) of SOM (energy release per unit SOM) declined with decreasing aggregate size in the 0- to 20-cm soil layer. Moreover, TG-T50 (the temperature resulting in 50% of SOM loss) correlated negatively to aggregate size, but DSC-T50 (the temperature at which 50% of energy resulting from organic matter combustion release) correlated positively to aggregate size. Compared with MP management, NT management improved quantity but decreased thermal stability of SOM in aggregates in the 0- to 5-cm layer, which was indicated by the greater weight loss at combustion, higher Exo1/Exotot ratio, greater energy densities and lower TG-T50. No tillage also led to increased stratification ratios of thermal labile and thermal recalcitrant SOM.
  • Authors:
    • Jabro, J. D.
    • Benjamin, J. G.
    • Hergert, G. W.
    • Mikha, M. M.
    • Nielsen, R. A.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 79
  • Issue: 2
  • Year: 2015
  • Summary: Long-term studies document that soil properties influenced by management practices occur slowly. The objectives of this study were to evaluate 70 yr of manure (M) and commercial fertilizer (F) additions and moldboard plowing on soil organic C (SOC), soil total N (STN), water-stable aggregates (WSA), and aggregate-associated C and N. The Knorr-Holden plots have been in furrow irrigated continuous corn (Zea mays L.) since 1912 on a Tripp sandy loam (coarse-silty, mixed, superactive, mesic Aridic Haplustoll). Soil samples were collected from the 0- to 5-, 5- to 10-, 10- to 15-, and 15- to 30-cm depths in 2011. Soils were fractionated by wet sieving into four aggregate-size classes (>1000, 500-1000, 250-500, and 53-250 mm). Continuous M amendment increased the SOC in the 0- to 30-cm depth approximately 1.7-fold compared with the F treatment. The combination of F + M further increased SOC in the 0- to 15-cm depth by approximately 36% for the M treatment receiving 90 kg N ha-1 of F (90 + M) and by 16% for the M treatment receiving 180 kg N ha-1 of F (180 + M) compared with the 15- to 30-cm depth. Macroaggregates increased with M and F + M when compared with F with the corresponding increase in microaggregate quantities associated with the F and no-N treatment. In the 0- to 30-cm depth, microaggregates were approximately 1.8 to 4.9 times greater than the macroaggregates. Aggregate-associated C masses were greater in microaggregates than in macroaggregates, which reflects greater amounts of microaggregates present in the soil. A significant, positive correlation was observed between SOC and aggregate-associated C. Overall, the addition of manure-based amendments, with or without F, increased SOC and enhanced aggregate stability.
  • Authors:
    • Tenorio, J. L.
    • Lopez-Solanilla, E.
    • Navas, M.
    • Garcia-Marco, S.
    • Tellez-Rio, A.
    • Vallejo, A.
  • Source: SCIENCE OF THE TOTAL ENVIRONMENT
  • Volume: 508
  • Year: 2015
  • Summary: Conservation agriculture that includes no tillage (NT) or minimum tillage (MT) and crop rotation is an effective practice to increase soil organic matter in Mediterranean semiarid agrosystems. But the impact of these agricultural practices on greenhouse gases (GHGs), such as nitrous oxide (N2O) and methane (CH4), is variable depending mainly on soil structure and short/long-term tillage. The main objective of this study was to assess the long-term effect of three tillage systems (NT, MT and conventional tillage (CT)) and land-covers (fallow/wheat) on the emissions of N2O and CH4 in a low N input agricultural system during one year. This was achieved by measuring crop yields, soil mineral N and dissolved organic C contents, and fluxes of N2O and CH4. Total cumulative N2O emissions were not significantly different (P > 0.05) among the tillage systems or between fallow and wheat The only difference was produced in spring, when N2O emissions were significantly higher (P < 0.05) in fallow than in wheat subplots, and NT reduced N2O emissions (P < 0.05) compared with MT and CT. Taking into account the water filled pore space (WFPS), both nitrification and denitrification could have occurred during the experimental period. Denitrification capacity in March was similar in all tillage systems, in spite of the higher DOC content maintained in the topsoil of NT. This could be due to the similar denitrifier densities, targeted by nirk copy numbers at that time. Cumulative CH4 fluxes resulted in small net uptake for all treatments, and no significant differences were found among tillage systems or between fallow and wheat land-covers. These results suggest that under a coarse-textured soil in low N agricultural systems, the impact of tillage on GHG is very low and that the fallow cycle within a crop rotation is not a useful strategy to reduce GHG emissions.
  • Authors:
    • Dalal, R. C.
    • Wang, W.
  • Source: European Journal of Agronomy
  • Volume: 66
  • Year: 2015
  • Summary: Farm management affects the global greenhouse gas (GHG) budget by changing not only soil organic carbon (SOC) stocks and nitrous oxide (N2O) emissions but also other pre-farm, on-farm and off-site emissions. The life cycle assessment (LCA) approach has been widely adopted to assess the "carbon footprint" of agricultural products, but rarely used as a tool to identify effective mitigation strategies. In this study, the global warming impacts of no-till (NT) vs. conventional till (CT), stubble retention (SR) vs. stubble burning (SB), and N fertilization (NF) vs. no N fertilization (N0) in an Australian wheat cropping system were assessed using in situ measurements of N2O fluxes over three years, SOC changes over forty years and including other supply chain GHG sources and sinks. The results demonstrated the importance of full GHG accounting compared to considering SOC changes or N2O emissions alone for assessing the global warming impacts of different management practices, and highlighted the significance of accurately accounting for SOC changes and N2O emissions in LCAs. The GHG footprints of wheat production were on averaged 475kg carbon dioxide equivalent (CO2-e) ha-1 (or 186kg CO2-e t-1 grain) higher under NF than N0. Where fertilizer N was applied (70kgNha-1), the life cycle emissions were 200kg CO2-e ha-1 (or 87t-1 grain) lower under NT than CT and 364kg CO2-e ha-1 (or 155t-1 grain) lower under SR than SB. Classification of the emission sources/sinks and re-calculation of published data indicated that under the common practices of SR combined with NT, N-related GHG emissions contributed 60-95% of the life cycle emissions in the predominantly rain-fed wheat production systems in Australia. Therefore, future mitigation efforts should aim to improve N use efficiency, explore non-synthetic N sources, and most importantly avoid excessive N fertilizer use whilst practising NT and SR.
  • Authors:
    • Zamberlan, J. F.
    • Reichardt, K.
    • Fiorin, J. E.
    • Roberti, D.
    • Keller, C.
    • Nora, D. D.
    • Amado, T. J. C.
    • Bortolotto, R. P.
    • Pasini, M. P. B.
    • Nicoloso, R. da S.
  • Source: African Journal of Agricultural Research
  • Volume: 10
  • Issue: 6
  • Year: 2015
  • Summary: Soil carbon dioxide flux is a complex process which depends on variations of different factors related to climate and soil. The objective of this study was identifying the abiotic factors that most contributed to this flux during different phonologic stages of the sequence black oat-vetch, cultivated under the no tillage system, in the winter, and find out the most important factors. Soil carbon fluxes were measured every 15 min with a LI-COR "long-term" (stationary) chamber, installed on the no tillage site of the rotation: soybean/black oat/soybean/black oat+vetch/corn/turnip/wheat. The factor that mostly influenced soil carbon fluxes was soil temperature, explaining 57% of the flux variation during the cycles of the crops and 80% from tillering to the begin of the elongation stage of the black oat. The phonologic stages of the black oat in the consortium black oat+vetch that mostly contributed to the carbon soil flux were from the begin of the tillering to the begin of the elongation, and from the elongation to massive grain of the black oat.
  • Authors:
    • Masilionyte, L.
    • Sasnauskiene, J.
    • Romaneckas, K.
    • Sarauskis, E.
    • Buragiene, S.
    • Kriauciuniene, Z.
  • Source: SCIENCE OF THE TOTAL ENVIRONMENT
  • Volume: 514
  • Year: 2015
  • Summary: Intensive agricultural production strongly influences the global processes that determine climate change. Thus, tillage can play a very important role in climate change. The intensity of soil carbon dioxide (CO 2) emissions, which contribute to the greenhouse effect, can vary depending on the following factors: the tillage system used, meteorological conditions (which vary in different regions of the world), soil properties, plant residue characteristics and other factors. The main purpose of this research was to analyse and assess the effects of autumn tillage systems with different intensities on CO 2 emissions from soils during different seasons and under the climatic conditions of Central Lithuania. The research was conducted at the Experimental Station of Aleksandras Stulginskis University from 2009 to2012; and in 2014. The soils at the experimental site were classified as Eutric Endogleyic Planosol (Drainic). The investigations were conducted using five tillage systems with different intensities, typical of the Baltic Region. Deep conventional ploughing was performed at a depth of 230-250 mm, shallow ploughing was conducted at a depth of 120-150 mm, deep loosening was conducted at depths of 250-270 mm, and shallow loosening was conducted at depths of 120-150 mm. The fifth system was a no-tillage system. Overall, autumn tillage resulted in greater CO 2 emissions from the soil over both short- and long-term periods under the climatic conditions of Central Lithuania, regardless of the tillage system applied. The highest soil CO 2 emissions were observed for the conventional deep ploughing tillage system, and the lowest emissions were observed for the no-tillage system. The meteorological conditions greatly influenced the CO 2 emissions from the soil during the spring. Soil CO 2 emissions were enhanced as precipitation and the air and soil temperatures increased. Long-term investigations regarding the dynamics of CO 2 emissions from soils during the maize vegetation period indicated that autumn tillage systems affect the total soil CO 2 emissions. The highest (2.17 mol m -2 s -1) soil CO 2 emissions during the vegetation period were observed in the deep ploughing tillage system, and the lowest values were observed (1.59 mol m -2 s -1) in the no-tillage system.
  • Authors:
    • Verhallen, E. A.
    • Hayes, A.
    • Congreves, K. A.
    • Van Eerd, L. L.
  • Source: Soil and Tillage Research
  • Volume: 152
  • Year: 2015
  • Summary: Long-term agricultural production with different tillage systems and crop rotations affect soil health, and thereby influence agricultural sustainability. However, quantifying and integrating the numerous soil health attributes is complex. One method of measuring overall soil health is the Cornell Soil Health Assessment (CSHA) used in New York; however, its applicability for other regions should be evaluated. Soil samples were collected from the 0-15. cm depth in 2009 and 2010 at four temperate, rainfed long-term experimental sites in Ontario (Ridgetown, Delhi, Elora, and Ottawa) and we evaluated the impact of tillage systems and crop rotations on 15 soil attributes. Based on a principal component analysis (PCA), the first two components accounted for 62% of the cumulative variability. The PCA eigenvectors were used to weight individual CSHA scores and develop the new Ontario Soil Health Assessment (OSHA) overall score. The OSHA scoring system was 2-10 times more sensitive than the CSHA in showing numerical differences for soil health among different tillage systems and crop rotations, which may help growers to more clearly see differences in soil health under different management practices. No-till (NT) compared to conventional tillage (CT) had significantly greater OSHA scores at Ridgetown, Delhi, and Elora, but there was no difference at Ottawa. At Ridgetown and Elora, crop rotations which included winter wheat or alfalfa tended to have higher OSHA scores, while lowest scores were with monoculture corn (monoC) or soybean-corn (S-C or S-S-C-C). This study provides the first soil health assessment for Ontario and a framework for improving overall soil health testing elsewhere.
  • Authors:
    • Lombardi, M.
    • Tricase, C.
    • Rana, R.
    • Ingrao, C.
  • Source: Applied Energy
  • Volume: 149
  • Year: 2015
  • Summary: Over the last few years, agro-biogas has been receiving great attention since it enables replacement of natural gas, thereby representing a tool which reduces greenhouse gas emissions and other environmental impacts. In this context, this paper is aimed at the application of the Carbon Footprint (CF) to an agro-biogas supply chain (SC) in Southern Italy, according to ISO/TS 14067:2013, so as to calculate the related 100-year Global Warming Potential (GWP100). The topic was addressed because agro-biogas SCs, though being acknowledged worldwide as sustainable ways to produce both electricity and heat, can be source of GHG emissions and therefore environmental assessments and improvements are needed. Additionally, the performed literature review highlighted deficiencies in PCF assessments, so this study could contribute to enriching the international knowledge on the environmental burdens associated with agro-biogas SCs. The analysis was conducted using a life-cycle approach, thus including in the assessment: functional unit choice, system border definition and inventory analysis development. The primary data needed was provided by a farm located in the province of Foggia (Apulia region in Southern Italy), already equipped with anaerobic digestion and cogeneration plant for biogas production and utilisation. Results from this study are in agreement with those found by some of the most relevant studies in the sector. Indeed, it was possible to observe that GWP100 was almost entirely due to cropland farming and, in particular, to the production of ammonium nitrate in the amount required for fertilisation. Furthermore, environmental credits were observed thanks to: carbon sequestration enabled by no-tillage practice; and avoided production of chemical fertiliser thanks to 50% organic farming. Based upon the results obtained, a sensitivity analysis was carried out, thus highlighting reduced environmental impacts if ammonium nitrate was replaced with urea.Finally, thanks to this study, all the target stakeholders will learn more about the input/output flows involved in the system analysed, the related environmental impacts and the improvements needed to reduce them. In this way, it could be possible to compare the analysed agro-biogas SC with others of equal functionality, and so to enable considerations to be made on the resulting similarities and differences in terms of methodological approach, inventory flows and environmental impact.