• Authors:
    • Ventrella, D.
    • Palumbo, A.
    • Niedda, M.
    • Giglio, L.
    • Castellini, M.
  • Source: Soil and Tillage Research
  • Volume: 154
  • Year: 2015
  • Summary: Biochar represents a soil conditioner that can change the physical and hydraulic properties of the soil. To date, little information is available about the biochar-induced changes on physical and hydraulic properties of fine textured soils. Therefore, an evaluation of its effects before the field use is advisable. The main objective of this investigation was to evaluate the impact of biochar addition on saturated (Kfs) and unsaturated (K(h)) hydraulic conductivity, water retention, capacitive indicators such as macroporosity (Pmac), air capacity (AC), plant available water (PAWC) and relative field capacity (RFC, equal to the ratio between field capacity and saturated soil water content), dry bulk density (ρb) of a repacked clay soil. Biochar effects on simulated wheat yields were also evaluated using the DSSAT model. Five levels of amendments (0-5-10-20-30g biochar per kg-1 soil) were used and the soil columns remained in the field for about 30 months until undisturbed soil conditions were reached. No significant differences of the Kfs values were detected between amended and unamended soils and the ratio between Kfs values was, on average, equal to a factor of 1.01-0.93-0.98-1.25 (respectively for C5-C10-C20-C30). In the same way, biochar did not affect appreciably the K(h) values. Depending on the applied pressure head or the biochar concentration, the differences were within a factor of 0.83-0.39. On the contrary, significant increases of soil water retention were detected close to water saturation (0 values was, on average, equal to a factor of 1.01-0.93-0.98-1.25 (respectively for C5-C10-C20-C30). In the same way, biochar did not affect appreciably the K(h) values. Depending on the applied pressure head or the biochar concentration, the differences were within a factor of 0.83-0.39. On the contrary, significant increases of soil water retention were detected close to water saturation (0 values was, on average, equal to a factor of 1.01-0.93-0.98-1.25 (respectively for C5-C10-C20-C30). In the same way, biochar did not affect appreciably the K(h) values. Depending on the applied pressure head or the biochar concentration, the differences were within a factor of 0.83-0.39. On the contrary, significant increases of soil water retention were detected close to water saturation (0b values, our results confirm that small decreases in bulk density (on average, 0.014gcm-3) may result in appreciable modifications in soil water retention close to water saturation. The simulations carried out with DSSAT suggested that a moderate addition of biochar to a clay soil (not higher than 10gkg-1) has the potential to increase the production of durum wheat (mean increase±standard deviation, 236±126kgha-1). These findings will have to be verified under field conditions. © 2015 Elsevier B.V.
  • Authors:
    • Larsen, E.
    • Grossman, J.
    • Hoyt, G.
    • Line, D.
    • Osmond, D.
    • Edgell, J.
  • Source: Journal of Environmental Quality Abstract - Surface Water Quality
  • Volume: 44
  • Issue: 6
  • Year: 2015
  • Summary: Organic agricultural systems are often assumed to be more sustainable than conventional farming, yet there has been little work comparing surface water quality from organic and conventional production, especially under the same cropping sequence. Our objective was to compare nutrient and sediment losses, as well as sweet corn ( Zea mays L. var. saccharata) yield, from organic and conventional production with conventional and conservation tillage. The experiment was located in the Appalachian Mountains of North Carolina. Four treatments, replicated four times, had been in place for over 18 yr and consisted of conventional tillage (chisel plow and disk) with conventional production (CT/Conven), conservation no-till with conventional production (NT/Conven), conventional tillage with organic production (CT/Org), and conservation no-till with organic production (NT/Org). Water quality (surface flow volume; nitrogen, phosphorus, and sediment concentrations) and sweet corn yield data were collected in 2011 and 2012. Sediment and sediment-attached nutrient losses were influenced by tillage and cropping system in 2011, due to higher rainfall, and tillage in 2012. Soluble nutrients were affected by the nutrient source and rate, which are a function of the cropping system. Sweet corn marketable yields were greater in conventional systems due to high weed competition and reduced total nitrogen availability in organic treatments. When comparing treatment efficiency (yield kg ha -1/nutrient loss kg ha -1), the NT/Conven treatment had the greatest sweet corn yield per unit of nutrient and sediment loss. Other treatment ratios were similar to each other; thus, it appears the most sustainably productive treatment was NT/Conven.
  • Authors:
    • Stuedemann, J.
    • Franzluebbers, A.
  • Source: Journal of Soil and Water Conservation
  • Volume: 70
  • Issue: 6
  • Year: 2015
  • Summary: Cover crops are a key component of conservation cropping systems. They can also be a key component of integrated crop-livestock systems by offering high-quality forage during short periods between cash crops. The impact of cattle grazing on biologically active soil carbon (C) and nitrogen (N) fractions has not received much attention. We investigated the impacts of tillage (conventional disk and no tillage) and cover crop management (ungrazed and grazed) on biologically active soil C and N fractions from biennial sampling during seven years of continuous management. Soil microbial biomass C was unaffected by cover crop management under conventional tillage, but was enhanced with grazing compared with no grazing under no tillage at a depth of 0 to 6 cm (0 to 2.4 in), as well as at 0 to 30 cm (0 to 12 in). The same effect occurred for the flush of carbon dioxide (CO2) following rewetting of dried soil during 3 days of incubation at a depth of 0 to 6 cm only, while it occurred for cumulative C mineralization during 24 days of incubation at a depth of 0 to 30 cm only. Grazing effects on net N mineralization during 24 days of incubation and residual soil inorganic N were nonexistent. All biologically active fractions of soil C and N were highly stratified with depth under no tillage and less so under conventional tillage. Cumulative stocks of soil C and N fractions to a depth of 0 to 30 cm were generally not significantly different between cover crop management systems, nor between tillage systems, except for (1) lower soil microbial biomass C with than without grazing under conventional tillage, (2) greater soil microbial biomass C with than without grazing under no tillage, and (3) lower cumulative C mineralization during 24 days under no tillage than under conventional tillage. Grazing of cover crops can be recommended as a strategy to promote greater adoption of cover cropping throughout the southeastern United States.
  • Authors:
    • Curtin, D.
    • Beare, M.
    • Gillespie, A.
    • Gregorich, E.
    • Sanei, H.
    • Yanni, S.
  • Source: Soil Biology and Biochemistry
  • Volume: 91
  • Issue: December 2015
  • Year: 2015
  • Summary: The stability of soil organic matter (SOM) as it relates to resistance to microbial degradation has important implications for nutrient cycling, emission of greenhouse gases, and C sequestration. Hence, there is interest in developing new ways to quantify and characterise the labile and stable forms of SOM. Our objective in this study was to evaluate SOM under widely contrasting management regimes to determine whether the variation in chemical composition and resistance to pyrolysis observed for various constituent C fractions could be related to their resistance to decomposition. Samples from the same soil under permanent pasture, an arable cropping rotation, and chemical fallow were physically fractionated (sand: 2000-50 m; silt: 50-5 m, and clay: <5 m). Biodegradability of the SOM in size fractions and whole soils was assessed in a laboratory mineralization study. Thermal stability was determined by analytical pyrolysis using a Rock-Eval pyrolyser, and chemical composition was characterized by X-ray absorption near-edge structure (XANES) spectroscopy at the C and N K-edges. Relative to the pasture soil, SOM in the arable and fallow soils declined by 30% and 40%, respectively. The mineralization bioassay showed that SOM in whole soil and soil fractions under fallow was less susceptible to biodegradation than that in other management practices. The SOM in the sand fraction was significantly more biodegradable than that in the silt or clay fractions. Analysis by XANES showed a proportional increase in carboxylates and a reduction in amides (protein) and aromatics in the fallow whole soil compared to the pasture and arable soils. Moreover, protein depletion was greatest in the sand fraction of the fallow soil. Sand fractions in fallow and arable soils were, however, relatively enriched in plant-derived phenols, aromatics, and carboxylates compared to the sand fraction of pasture soils. Analytical pyrolysis showed distinct differences in the thermal stability of SOM among the whole soil and their size fractions; it also showed that the loss of SOM generally involved preferential degradation of H-rich compounds. The temperature at which half of the C was pyrolyzed was strongly correlated with mineralizable C, providing good evidence for a link between the biological and thermal stability of SOM.
  • Authors:
    • Pitombo, L.M.
    • Carmo, J.B.
    • Maria, I.C.
    • Andrade, C.A.
  • Source: Scientia Agricola
  • Volume: 72
  • Issue: 2
  • Year: 2015
  • Summary: The large volume of sewage sludge (SS) generated with high carbon (C) and nutrient content suggests that its agricultural use may represent an important alternative to soil carbon sequestration and provides a potential substitute for synthetic fertilizers. However, emissions of CH 4 and N 2O could neutralize benefits with increases in soil C or saving fertilizer production because these gases have a Global Warming Potential (GWP) 25 and 298 times greater than CO 2, respectively. Thus, this study aimed to determine C and N content as well as greenhouse gases (GHG) fluxes from soils historically amended with SS. Sewage sludge was applied between 2001 and 2007, and maize ( Zea mays L.) was sowed in every year between 2001 and 2009. We evaluated three treatments: Control (mineral fertilizer), 1SS (recommended rate) and 2SS (double rate). Carbon stocks (0-40 cm) were 58.8, 72.5 and 83.1 Mg ha -1 in the Control, 1SS and 2SS, respectively, whereas N stocks after two years without SS treatment were 4.8, 5.8, and 6.8 Mg ha -1, respectively. Soil CO 2 flux was highly responsive to soil temperature in SS treatments, and soil water content greatly impacted gas flux in the Control. Soil N 2O flux increased under the residual effects of SS, but in 1SS, the flux was similar to that found in moist tropical forests. Soil remained as a CH 4 sink. Large stores of carbon following historical SS application indicate that its use could be used as a method for carbon sequestration, even under tropical conditions.
  • Authors:
    • Danert, C.
    • Vera, J. C.
    • Portocarrero, R.
    • Acreche, M. M.
    • Valeiro, A. H.
  • Source: Sugar Tech
  • Volume: 16
  • Issue: 2
  • Year: 2014
  • Summary: Concentrations of greenhouse gases (GHG) in the atmosphere are increasing due to anthropogenic actions, and agriculture is one of the most important contributors. This study quantified GHG emissions from green-cane harvested sugarcane with and without post-harvest burning in Tucuman (Argentina). A field trial was conducted in Tucuman during the 2011/2012 season using a randomised complete-block design with four replications. Treatments were: (a) harvest without sugarcane burning (neither before nor after), and (b) harvest with trash burnt after harvest. The method used to capture gases (CO2, CH4 and N2O) in the crop cycle was based on closed-vented chambers, while quantification was by gas chromatography. There were significant emission rates of CO2 and N2O during the sugarcane cycle in Tucuman, but no evidence of CH4 emissions or uptakes. N2O and CO2 emission rates were higher in the no-burning treatment than in the burnt, but only in part of the crop cycle. The former is apparently associated with the application of nitrogen fertiliser, while the higher CO2 emissions seem to be associated with trash retention. There were no significant correlations between environmental factors and emission rates. Although these results seem pessimistic, in the context of an entire crop GHG balance (including the emissions due to burning before or after harvest) green-cane harvesting without burning could effectively lead to a reduction of total GHG emissions during the crop cycle.
  • Authors:
    • Herridge, D.
    • Guppy, C.
    • Begum, N.
    • Schwenke, G.
  • Source: Biology and Fertility of Soils
  • Volume: 50
  • Issue: 3
  • Year: 2014
  • Summary: Few studies have compared emissions of nitrous oxide (N2O), the potent greenhouse gas associated with decomposition of both below-ground (root) and above-ground (shoot) residues. We report a laboratory incubation experiment to evaluate effects of root and shoot residues from wheat, canola, soybean, and sorghum, incorporated into a naturally fertile acidic Black Vertisol, on N2O and carbon dioxide (CO2) emissions. The residue-amended Vertisol samples were incubated at 25 A degrees C and 70 % water-filled pore space (WFPS) to facilitate denitrification activity for a total period of 56 days. The incubated soils were periodically sampled for N2O, CO2, mineral N, and dissolved organic carbon (DOC). In general, shoot residues emitted more CO2 than roots, while N2O emissions were 50-70 % higher in cereal root residues than those in shoots. Surprisingly, the highest N2O emissions were associated with soils amended with the more inert high C/N ratio residues (wheat and sorghum roots), and to some extent, lowest emissions were associated with low C/N ratio (more labile) residues, particularly during the early stages of incubation (0-22 days). During this stage, there was a significant (p < 0.01) and negative correlation between N2O emissions and microbial respiration (CO2 efflux) and a positive (p < 0.001) correlation between microbial respiration and DOC. These results suggest that residue decomposition linked to N immobilization reduced N2O emissions during this early stage. Only, later in the study (23-56 days), did the high %N, low C/N ratio residues of soybean shoot and canola roots release at least twice as much N2O as the majority of the other treatments. We concluded that the unexpected patterns of N2O emissions were a result of the initially high mineral N content of the incubated soils and that root residues are likely to contribute substantially to emissions from cropping soils.
  • Authors:
    • Pan, G.
    • Parton, W. J.
    • Ogle, S. M.
    • Cheng, K.
  • Source: Global Change Biology
  • Volume: 20
  • Issue: 3
  • Year: 2014
  • Summary: Understanding the potential for greenhouse gas (GHG) mitigation in agricultural lands is a critical challenge for climate change policy. This study uses the DAYCENT ecosystem model to predict GHG mitigation potentials associated with soil management in Chinese cropland systems. Application of ecosystem models, such as DAYCENT, requires the evaluation of model performance with data sets from experiments relevant to the climate and management of the study region. DAYCENT was evaluated with data from 350 cropland experiments in China, including measurements of nitrous oxide emissions (N2O), methane emissions (CH4), and soil organic carbon (SOC) stock changes. In general, the model was reasonably accurate with R2 values for model predictions vs. measurements ranging from 0.71 to 0.85. Modeling efficiency varied from 0.65 for SOC stock changes to 0.83 for crop yields. Mitigation potentials were estimated on a yield basis (Mg CO2-equivalent Mg−1Yield). The results demonstrate that the largest decrease in GHG emissions in rainfed systems are associated with combined effect of reducing mineral N fertilization, organic matter amendments and reduced-till coupled with straw return, estimated at 0.31 to 0.83 Mg CO2-equivalent Mg−1Yield. A mitigation potential of 0.08 to 0.36 Mg CO2-equivalent Mg−1Yield is possible by reducing N chemical fertilizer rates, along with intermittent flooding in paddy rice cropping systems.
  • Authors:
    • Balarezo Giarola, N.
    • Tormena, C.
    • Ball, B.
    • da Silva, A.
    • Locks Guimaraes, R.
  • Source: Scientia Agricola
  • Volume: 71
  • Issue: 2
  • Year: 2014
  • Summary: No-tillage in Brazil is an efficient agricultural system that improves crop productivity whilst controlling erosion caused to the soil by degradation. However, there is some concern regarding soil compaction. Our objective was to determine whether the function of soil structure in sustaining crop growth was dependent on row and interrow positions in long-term no-tillage. We took soil samples from a field in a commercial farm under long-term no-tillage since 1979 on a clayey Oxisol in Southern Brazil. We assessed soil physical quality using the revised Peerlkamp technique and measured bulk density, air-filled porosity and air permeability of intact soil cores. Samples were incubated to assess in vitro N2O and CO2 production. The soil physical and structural properties showed consistent differences between interrow and row positions, where the properties measured were more favorable. The revised Peerlkamp technique proved as efficient as quantitative parameters in discriminating treatment differences. Overall, soil physical conditions in the interrow were less favourable than in the row. Pore continuity did not vary as regards position. This may explain why row position did not influence in vitro N2O and CO2 production. Soil physical quality under no-tillage system is enhanced, at least in the short term, by superficial disturbances in the row as a result of the action of the coulters of the no-tillage seeder.
  • Authors:
    • Baudino, C.
    • Peano, C.
    • Girgenti, V.
    • Tecco, N.
  • Source: Science of the Total Environment
  • Volume: 473
  • Year: 2014
  • Summary: In this study, we analysed the environmental profile of the strawberry industry in Northern Italy. The analysis was conducted using two scenarios as reference systems: strawberry crops grown in unheated plastic tunnels using currently existing cultivation techniques, post-harvest management practices and consumption patterns (scenario I) and the same strawberry cultivation chain in which some of the materials used were replaced with bio-based materials (scenario 2). In numerous studies, biodegradable polymers have been shown to be environmentally friendly, thus potentially reducing environmental impacts. These materials can be recycled into carbon dioxide and water through composting. Many materials, such as Mater-BI (R) and PLA (R) are also derived from renewable resources. The methodology chosen for the environmental analysis was a life cycle assessment (LCA) based on a consequential approach developed to assess a product's overall environmental impact from the production system to its usage and disposal. In the field stage, a traditional mulching film (non-biodegradable) could be replaced with a biodegradable product. This change would result in waste production of 0 kg/ha for the bio-based product compared to 260 kg/ha of waste for polyethylene (PE). In the post-harvest stage, the issue addressed was the use and disposal of packaging materials. The innovative scenario evaluated herein pertains to the use of new packaging materials that increase the shelf life of strawberries, thereby decreasing product losses while increasing waste management efficiency at the level of a distribution platform and/or sales outlet. In the event of product deterioration or non-sale of the product, the packaging and its contents could be collected together as organic waste without any additional processes because the packaging is compostable according to EN13432. Scenario 2 would achieve reductions of 20% in the global warming potential and non-renewable energy impact categories. (C) 2013 Elsevier B.V. All rights reserved.