Changes in soil fertility parameters and the environmental effects in a rapidly developing region of China

An extensive knowledge of the temporal variability of soil fertility parameters and how this variation affects the environment is imperative to a wide range of disciplines within agricultural science for optimal crop production and ecosystem preservation. This paper examines the temporal variability of soil pH, organic matter (OM), cation exchange capacity (CEC), total nitrogen (TN), total phosphorus (TP), available phosphorus (P_Av), and available potassium (K_Av) on Cambosols (Entisols) (n = 179) and Anthrosols (Inceptisols) (n = 95) in Zhangjiagang County, China from 1980 to 2004. Nutrient input was monitored from 1983 to 2004. Annual N fertilizer rates were significantly different during three periods (1983–1989, 1989–1999, 1999–2004), where annual rates increased significantly after 1989 and then decreased after 1999. Annual P fertilizer rates were significantly different during two periods (1983–1993, 1993–2004) where annual rates increased after 1993. No change was found in K fertilizer rates. Soil pH marginally increased by 0.14 units in Cambosols, but significantly decreased by 1.02 units in Anthrosols. OM, CEC, and TN increased in both soil orders an average of 2.15 g kg^?1, 1.6 cmol kg^?1, and 0.21 g kg^?1, respectively. TP decreased in Anthrosols by 70 mg kg^?1, P_Av increased in Cambosols by 4.83 mg kg^?1, and K_Av decreased in Cambosols by 15 mg kg^?1. Fertilizer input rates are causing nutrient imbalances, contributing to acidification in Anthrosols, and decreasing C/N ratios. Nutrient loading of N and deficiency of K is also a potential problem in the area. Efforts should be made to readjust soil nutrient inputs to reach an optimal, sustainable level.     

Comparing carbon fluxes between different stages of secondary succession of a karst grassland

Abandonment of marginal agricultural areas with subsequent secondary succession is a widespread type of land use change in Mediterranean and mountain areas of Europe, leading to important environmental consequences such as change in the water balance, carbon cycling, and regional climate. Paired eddy flux measurement design with grassland site and tree/shrub encroached site has been set-up in the Slovenian Karst (submediterranean climate region) to investigate the effects of secondary succession on ecosystem carbon cycling. The invasion of woody plant species was found to significantly change carbon balance shifting annual NEE from source to an evident sink. According to one year of data succession site stored ?126 ± 14 g C m^?2 y^?1 while grassland site emitted 353 ± 72 g C m^?2 y^?1. In addition, the seasonal course of CO₂ exchange differed between both succession stages, which can be related to differences in phenology, i.e. activity of prevailing plant species, and modified environmental conditions within forest fragments of the invaded site. Negligible effect of instrument heating was observed which proves the Burba correction in our ecosystems unnecessary. Unexpectedly high CO₂ emissions and large disagreement with soil respiration especially on the grassland site in late autumn indicate additional sources of carbon which cannot be biologically processes, such as degassing of soil pores and caves after rain events.     

Hollow TiO2 spheres with improved visible light photocatalytic activity synergistically enhanced by multi-stimulative: Morphology advantage, carbonate-doping and the induced Ti3 +

Great efforts have been devoted to improve the photocatalytic activity of TiO_2 in the visible light region. Rational design of the external structure and adjustment of intrinsic electronic status by impurity doping are two main effective ways to achieve this purpose. A facile onepot synthetic approach was developed to prepare C-doped hollow TiO_2 spheres, which simultaneously realized these advantages. The synthesized TiO_2 exhibits a mesoporous hollow spherical structure composed of fine nanocrystals, leading to high specific surface area(~180 m~2/g) and versatile porous texture. Carbonate-doping was achieved by a postthermal treatment at a relatively low temperature(200°C), which makes the absorption edge red-shifted to the visible region of the solar spectrum. Concomitantly, Ti~(3+) induced by C-doping also functions in improving the visible-light photocatalytic activity by reducing the band gap. There exists a synergistic effect from multiple stimulatives to enhance the photocatalytic effect of the prepared TiO_2 catalyst. It is not out of expectation that the asprepared C-doped hollow TiO_2 spheres exhibits an improved photocatalytic activity under visible light irradiation in organic pollutant degradation.     

Evidence of rich microbial communities in the subsoil of a boreal acid sulphate soil conducive to greenhouse gas emissions

The largest areas of acid sulphate (AS) soils in Europe are located in Finland, where 67,000–130,000 ha of AS soils are in agricultural use. In addition to their acidifying effects on waters, AS soils might be a significant source of greenhouse gases. In this pilot research, carbon and nitrogen content and microbial activity were studied in an AS and a non-AS soil. Large carbon and nitrogen stocks (110 Mg C_org ha^?1 and 15 Mg N_tot ha^?1) as well as high substrate induced respiration (33 μg CO₂–C g^?1h^?1) were found in the C horizons of the AS soil but not in the non-AS soil. High microbial activity in these horizons of the AS soil was further confirmed by the measurement of dehydrogenase activity, basal respiration, the numbers of culturable bacterial cells, and the ratio of culturable to total numbers of cells. Still, the denitrifying enzyme activity was very low in the anaerobic horizons of the AS soil, indicating the prevalence of microbes other than denitrifiers. We suspect that the microbial community originated with the genesis of AS soil and has been supported by the large stocks of accumulated carbon and mineral nitrogen in the C horizons. If these permanently water-saturated subsoils are exposed to oxygen and their microbial activity consequently increases, large carbon and nitrogen stocks are likely to be mobilised, resulting in increased emission of greenhouse gases. Additional studies of boreal AS soils are needed to assess their potential contribution to increases in greenhouse gas fluxes at the local, regional, and global scales.     

Carbon footprint of sugar produced from sugarcane in eastern Thailand

Carbon footprint (CFP) of sugar produced from sugarcane in eastern Thailand was estimated from greenhouse gas emissions (CO₂, CH₄, and N₂O) during the sugarcane cultivation and milling process. The use of fossil fuels, chemical and organic fertilizer and sugarcane biomass data during cultivation were collected from field surveys, questionnaires and interviews. Sugar mill emissions, fossil fuel utilization and greenhouse gas emission from wastewater treatments were included. The results show that sugar production has a carbon footprint of 0.55 kg CO₂e kg^?1 sugar. This carbon footprint was a sum of 0.49 kg CO₂e kg^?1 sugar from sugarcane cultivation and 0.06 kg CO₂e kg^?1 sugar from the milling process. For the cultivation part, most of the GHGs emissions were from fertilizer, fossil fuel use and biomass burning. The CFP in eastern Thailand is sensitive to the type of data selected for calculation and of variations of farm inputs during sugarcane cultivation. There was no significant difference of CFP among farm sizes, although small farms tended to give a relatively higher CFP than that of medium and large farms.     

Photo-catalytic reduction of carbon dioxide with in-situ synthesized CoPc/TiO2 under visible light irradiation

CO₂ is photo-catalytically reduced to produce formic acid, methanol, formaldehyde in an aqueous solution using visible light irradiation and in-situ synthesized CoPc/TiO₂. CoPc/TiO₂ nano-composite is in-situ synthesized through the annulations of 1,2-dicyanobenzene on the surface of TiO₂ with Co(II) as template. The prepared catalysts are characterized by means of XRD, DTA–TG, UV–vis and FT-IR methods. The photo-catalytic activity of these catalysts under visible light is discussed. The experimental results indicate that cobalt-phthalocyanine (CoPc) and TiO₂ are indeed synthesized by the in-situ method. Under the visible light irradiation, CoPc molecules are excited first and the excited electrons are injected into the conduction band of TiO₂, then the separation of electron–hole pairs is increased so that the photo-catalytic efficiency is increased. The results show that the in-situ CoPc/TiO₂ out performed physical absorbed CoPc/TiO₂. The total organic carbon (TOC) yield of 0.7 wt.% in-situ CoPc/TiO₂ is 1714.9 μmol/g catal. following 10 h of visible light illumination. The yield is much higher than those of TiO₂ and physical absorbed CoPc/TiO₂.     

Comparison between background concentrations of arsenic in urban and non-urban areas of Florida

Arsenic contamination is of great environmental concern due to its toxic effects as a carcinogen. Knowledge of arsenic background concentrations is important for land application of wastes and for making remediation decisions. The soil clean-up target level for arsenic in Florida (0.8 and 3.7 mg kg⁻¹ for residential and commercial areas, respectively) lies within the range of both background and analytical quantification limits. The objective of this study was to compare arsenic distribution in urban and non-urban areas of Florida. Approximately 440 urban and 448 non-urban Florida soil samples were compared. For urban areas, soil samples were collected from three land-use classes (residential, commercial and public land) in two cities, Gainesville and Miami. For the non-urban areas, samples were collected from relatively undisturbed non-inhabited areas. Arsenic concentrations varied greatly in Gainesville, ranging from 0.21 to approximately 660 mg kg⁻¹ with a geometric mean (GM) of 0.40 mg kg⁻¹, which were lower than Miami samples (ranging from 0.32 to 112 mg kg⁻¹; GM=2.81 mg kg⁻¹). Arsenic background concentrations in urban soils were significantly greater and showed greater variation than those from relatively undisturbed non-urban soils (GM=0.27 mg kg⁻¹) in general.     

Effectiveness of buffer strips in removing pollutants in runoff from a cultivated field in North-East Italy

Buffer strips are an efficient and economical way to reduce agricultural nonpoint source pollution. Local researches are necessary to gain information on buffer performance, with particular emphasis on narrow buffers. The effect of a 6 m buffer strip (BS) in reducing runoff, suspended solids and nutrients from a field growing maize, winter wheat and soybean was assessed in a field experiment conducted in North-East Italy during 1998–2001. The BS was composed of two rows of regularly alternating trees (Platanus hybrida Brot.) and shrubs (Viburnum opulus L.), with grass (Festuca arundinacea L.) in the inter-rows.The BS reduced total runoff by 78% compared to no-BS, in which cumulative runoff depth was 231 mm over 4 years. With no-BS runoff appeared to be influenced mostly by total rainfall, while with BS maximum rainfall intensity was more important. The filtering effect of the BS reduced total suspended solids (TSS), particularly after the second year, when the median yearly concentrations ranged from 0.28 to 0.99 mg L⁻¹ and were smaller than 0.14 mg L⁻¹, with no-BS and with BS respectively. The combination of lower concentrations and runoff volumes significantly reduced TSS losses from 6.9 to 0.4 t ha⁻¹ over the entire period.A tendency to increased concentrations of all forms of N (total, nitrate and ammonium) while passing through the BS was observed, but total N losses were reduced from 17.3 to 4.5 kg ha⁻¹ in terms of mass balance. On the contrary, P concentrations were unmodified (soluble P), or lowered (total P) by the BS, reducing total losses by about 80%. The effect on total P, composed mainly of sediment-bound forms, was related to particulate settling when passing through the BS.A numerical index (Eutrophic Load Index), integrating water quality and runoff volumes, was created to evaluate the eutrophication risk of runoff with or without the BS. It showed that the BS effect was mostly due to a reduction of runoff volumes rather than improving the overall water quality.     

Biological hydrogen production by Rhodobacter capsulatus in solar tubular photo bioreactor

The purpose of this study was to develop a pilot scale tubular photo bioreactor (80 L) for photo fermentative hydrogen production by photosynthetic purple-non-sulfur bacterium, Rhodobacter capsulatus, operating in outdoor conditions, using acetate as the carbon source. The reactor was operated continuously in fed-batch mode for 30 days throughout December 2008 in Ankara. It was placed in a greenhouse in order to keep the temperature above freezing levels. It was found that R. capsulatus had a rapid growth with a specific growth rate of 0.025 h^?1 in the exponential phase. The growth was defined with modified logistic model for long term duration. The hydrogen production and feeding started in the late exponential phase. Evolved gas contained 99% hydrogen and 1% carbon dioxide by volume. The average molar productivity calculated during daylight hour was 0.31 mol H₂/(m³ h) with regard to the total reactor volume and 0.112 mol H₂/(m²·day) with regard to the total illuminated surface area. It was proven that even at low light intensities and low temperatures, the acetic acid which was fed to the system can be utilized for biosynthesis, growth and hydrogen production. The overall hydrogen yield was 0.6 mole H₂ per mole of acetic acid fed. This study showed that photofermentation in a pilot scale tubular photo bioreactor can produce hydrogen, even in winter conditions.     

Performance and water-use efficiency (single-leaf vs. whole-canopy) of well-watered and half-stressed split-root Lambrusco grapevines grown in Po Valley (Italy)

‘Lambrusco a foglia frastagliata’ grapevines (Vitis vinifera L.) were grown outdoors at Piacenza (44°55′N, 9°44′E, Po Valley, Italy) with the root system split between two 30-L pots and subjected from pre-veraison (17 July) to harvest (5 September) to soil drying of half of the root system (HS) induced by withholding water from one of the two pots as compared to well-watered (WW) vines (both pots daily recharged at field capacity). Volumetric soil-water content, pre-dawn and mid-morning leaf water potential, single-leaf gas-exchange as assimilation rate, stomatal conductance and transpiration were monitored throughout the trial. Whole-canopy gas-exchange as net CO₂ exchange rate (NCER) and transpiration were tracked from 31 August to 7 September on three vines per treatment on a 24-h basis using an enclosure method. Primary leaf carbon isotope (δ¹³C) composition, yield components and must composition were determined at harvest.Withdrawing water from one pot triggered a water stress response showing higher stomatal sensitivity to changes in air vapour pressure deficit, relatively low assimilation rates, high intrinsic and extrinsic water-use efficiency (WUE) and earlier cessation of shoot growth. Yet, mid-morning leaf water potential was consistently lower in HS treatment over stress as compared to WW, indicating an anisohydric adjustment. Canopy NCER given on a leaf-area basis showed mean daily rates ranging from 3.9 to 4.9 μmol m² s^?1 in WW canopies against 2.6–3.0 μmol m^?2 s^?1 in HS. Conversely, canopy transpiration rates varied from 0.915 to 1.157 mmol m^?2 s^?1 for WW to 0.630–0.714 mmol m² s^?1 in HS. Increased leaf-based intrinsic and extrinsic WUE in HS did not match the canopy response, which to some extent resulted in an opposite outcome, i.e. higher canopy WUE in well-watered vines especially in the morning hours. Likewise, δ¹³C did not differ between treatments. This suggests caution when point-time determinations of single-leaf-based WUE are extrapolated to the whole-canopy behaviour when assessing the water saving strategies of a given genotype. The stressed vines achieved no variation in yield level and components and had improved grape composition as to soluble solids and total anthocyanins. This optimal behaviour is likely due to earlier shoot growth cessation, enhanced maturity and a buffering leaf-to-fruit ratio (3.61 m² kg^?1) that mitigated the effects of post-veraison stress.     

Soil-profile organic carbon and total nitrogen during 12 years of pasture management in the Southern Piedmont USA

Soil organic C (SOC) and total soil N (TSN) sequestration estimates are needed to improve our understanding of management influences on soil fertility and terrestrial C cycling related to greenhouse gas emission. We evaluated the factorial combination of nutrient source (inorganic, mixed inorganic and organic, and organic as broiler litter) and forage utilization (unharvested, low and high cattle grazing pressure, and hayed monthly) on soil-profile distribution (0–150 cm) of SOC and TSN during 12 years of pasture management on a Typic Kanhapludult (Acrisol) in Georgia, USA. Nutrient source rarely affected SOC and TSN in the soil profile, despite addition of 73.6 Mg ha^?1 (dry weight) of broiler litter during 12 years of treatment. At the end of 12 years, contents of SOC and TSN at a depth of 0–90 cm under haying were only 82 ± 5% (mean ± S.D. among treatments) of those under grazed management. Within grazed pastures, contents of SOC and TSN at a depth of 0–90 cm were greatest within 5 m of shade and water sources and only 83 ± 7% of maximum at a distance of 30 m and 92 ± 14% of maximum at a distance of 80 m, suggesting a zone of enrichment within pastures due to animal behavior. During 12 years, the annual rate of change in SOC (0–90 cm) followed the order: low grazing pressure (1.17 Mg C ha^?1 year^?1) > unharvested (0.64 Mg C ha^?1 year^?1) = high grazing pressure (0.51 Mg C ha^?1 year^?1) > hayed (?0.22 Mg C ha^?1 year^?1). This study demonstrated that surface accumulation of SOC and TSN occurred, but that increased variability and loss of SOC with depth reduced the significance of surface effects.     

Ammonia and nitrous oxide emissions following land application of high and low nitrogen pig manures to winter wheat at three growth stages

Nitrous oxide (N₂O) and ammonia (NH₃) emissions from surface applied high (HN) and low (LN) nitrogen pig manures were measured under field conditions. Manures were band-spread to a winter wheat crop at three growth stages—mid-tillering, stem elongation and flag leaf emergence. The N₂O flux rates were measured using the static chamber technique while NH₃ volatilisation was assessed using a micrometeorological mass balance technique with passive flux samplers. The N₂O emissions were episodic in nature with flux rates observed ranging from 2.8 to 31.5 g N₂O–N ha^?1 day^?1 (P < 0.001). Higher N₂O emissions generally occurred after rainfall events. Highest N₂O losses were observed from the HN treatment with LN manure use decreasing emissions by 18% (P < 0.03). The NH₃ volatilisation rates were highest within 1 h of manure application with 95% of emissions occurring within 24 h (P < 0.001). Cumulative N loss was highest at mid-tillering as low crop canopy cover and increased wind-speeds enhanced NH₃ loss (P < 0.001). Highest emissions were measured from the HN manure (P < 0.03). Total ammoniacal N loss ranged from 6 to 11%. Crop N uptake and grain yield were unaffected by application timing or manure type. Therefore, the use of LN manures decreased gaseous emissions of N₂O and NH₃ without any adverse effects on crop performance.     

Streamwater phosphorus and nitrogen across a gradient in rural–agricultural land use intensity

This paper provides an overview of the impacts of rural land use on lowland streamwater phosphorus (P) and nitrogen (N) concentrations and P loads and sources in lowland streams. Based on weekly water quality monitoring, the impacts of agriculture on streamwater P and N hydrochemistry were examined along a gradient of rural–agricultural land use, by monitoring three sets of ‘paired’ (near-adjacent) rural headwater streams, draining catchments which are representative of the major geology, soil types and rural/agricultural land use types of large areas of lowland Britain. The magnitude and timing of P and N inputs were assessed and the load apportionment model (LAM) was applied to quantify ‘continuous’ (point) source and ‘flow-dependent’ (diffuse) source contributions of P to these headwater streams. The results show that intensive arable farming had only a comparatively small impact on streamwater total phosphorus (TP loads), with highly consistent stream diffuse-source TP yields of ca. 0.5 kg-P ha^?1 year^?1 for the predominantly arable catchments with both clay and loam soils, compared with 0.4 kg-P ha^?1 year^?1 for low agricultural intensity grassland/woodland on similar soil types. In contrast, intensive livestock farming on heavy clay soils resulted in dramatically higher stream diffuse-source TP yields of 2 kg-P ha^?1 year^?1. The streamwater hydrochemistry of the livestock-dominated catchment was characterised by high concentrations of organic P, C and N fractions, associated with manure and slurry sources. Across the study sites, the impacts of human settlement were clearly identifiable with effluent inputs from septic tanks and sewage treatment works resulting in large-scale increases in soluble reactive phosphorus (SRP) loads and concentrations. At sites heavily impacted by rural settlements, SRP concentrations under baseflow conditions reached several hundred μg-P L^?1. Load apportionment modelling demonstrated significant ‘point-source’ P inputs to the streams even where there were no sewage treatment works within the upstream catchment. This indicates that, even in sparsely populated rural headwater catchments, small settlements and even isolated groups of houses are sufficient to cause significant nutrient pollution and that septic tank systems serving these rural communities are actually operating as multiple point sources, rather than a diffuse input.     

The role of indicator choice in quantifying the threat of atmospheric ammonia to the ‘Natura 2000’ network

New ‘critical levels’ (CLE) for assessing the effects of atmospheric ammonia on sensitive ecosystems have recently been adopted by the United Nations Economic Commission for Europe (UNECE) of 1 and 3 [2–4] μg NH₃ m^?3 of ambient air (including water vapour), for different species sensitivities and their associated habitats. Based on these values, we examined how indicator choice affects estimates of stock-at-risk in the European ‘Natura 2000’ network.We applied an atmospheric model, FRAME, to estimate surface air concentrations of ammonia at 5 km and 1 km resolution for the UK network of Natura sites, optionally including calibration with the National Ammonia Monitoring Network. As a base indicator, we estimated the overall percentage area of the UK Natura network that exceeded critical level thresholds (‘Area Weighted Indicator’, AWI). We compared this with an alternative approach, estimating the percentage number of Natura sites where the critical level was exceeded (‘Designation Weighted Indicator’, DWI), which we consider more relevant under the terms of the Habitats Directive.Using the AWI (with 1 km calibrated ammonia), we estimate that 11.2%, 1.3% and 0.2% area of the UK Natura network exceeds the critical level values of 1, 2 and 3 μg NH₃ m^?3, respectively. By contrast, using the DWI, the equivalent exceedances are 59.1%, 23.6% and 9.8%. The highest regional exceedance (DWI, critical level 1 μg NH₃ m^?3) was calculated for England (91.9% exceeded), and the lowest for Scotland (24.0% exceeded). High resolution maps show that the larger threat estimated by the DWI approach is explained by (i) an anti-correlation between NH₃ concentration and Natura site area and (ii) the fact that exceedance over part of a Natura site is considered to represent a threat to the integrity of the whole site.     

Minimizing greenhouse gas emissions through the application of solar thermal energy in industrial processes

The analysis of industrial energy usage indicates that low temperature processes (20 ≈ 200 °C) are used in nearly all industrial sectors. In principle there is the potential to use solar thermal energy in these lower temperature processes thus, reducing the environmental impact of burning fossil fuels. Using the model of an Austrian dairy plant, this research investigated the potential for, and the economic viability of, using solar energy heat processes in industry.Some industrial sectors such as food, chemistry, plastic processing, textile industry, building materials industry and business establishments can be identified as potential sectors for the application of solar energy heat processes. When assessing the (economic) feasibility of solar thermal energy, the investigation of these industries’ energy systems has to focus on an integrated analysis of cooling and heating demands and to take into account competing technologies. Amongst these are heat integration, cogeneration, new technologies and heat pumps. Pinch analysis was used to investigate industrial energy systems and heat integration possibilities and proved to be a viable tool. Working from the basis of energy balances, Sankey diagrams, pinch analysis and environmental cost accounting, a newly developed investigation tool was applied in the case study of an Austrian dairy plant. This enabled a fast optimization of the system. Two different options for the integration of solar thermal energy into the production line were calculated, option 1 with a solar field of 1000 m² and option 2 with a solar field of 1500 m². Natural gas savings of 85,000 for option 1 and 109,000 m³/a for option 2 can be achieved, resulting in a reduction of 170 tons of CO₂ per year, or 218 tons for options 1 and 2 respectively. Based upon option 1, return on investment is realised after less than three years of implementation. This research thus, indicates promising technical and economical feasibility of using solar thermal energy for industrial processes and provides an important step towards sustainable zero emission production in industry.     

Long-term impact of a gliricidia-maize intercropping system on carbon sequestration in southern Malawi

Tree/crop systems under agroforestry practice are capable of sequestering carbon (C) in the standing biomass and soil. Although studies have been conducted to understand soil organic C increases in some agroforestry technologies, little is known about C sequestered in simultaneous tree/crop intercropping systems. The main objective of this study was to determine the effect of agroforestry practice on C sequestration and CO₂-C efflux in a gliricidia-maize intercropping system. The experiment was conducted at an experimental site located at the Makoka Agricultural Research Station, in Malawi. The studies involved two field plots, 7-year (MZ21) and 10-year (MZ12), two production systems (sole-maize and gliricidia-maize simultaneous intercropping systems). A 7-year-old grass fallow (Grass-F) was also included. Gliricidia prunings were incorporated at each time of tree pruning in the gliricidia-maize. The amount of organic C recycled varied from 0.8 to 4.8 Mg C ha⁻¹ in gliricidia-maize and from 0.4 to 1.0 Mg C ha⁻¹ in sole-maize. In sole-maize, net decreases of soil carbon of 6 Mg C ha⁻¹ at MZ12 and 7 Mg C ha⁻¹ at MZ21 in the topsoil (0–20 cm) relative to the initial soil C were observed. After 10 years of continuous application of tree prunings C was sequestered in the topsoil (0–20 cm) in gliricidia-maize was 1.6 times more than in sole-maize. A total of 123–149 Mg C ha⁻¹ were sequestered in the soil (0–200 cm depth), through root turnover and pruning application in the gliricidia-maize system. Carbon dioxide evolution varied from 10 to 28 kg ha⁻¹ day⁻¹ in sole-maize and 23 to 83 kg ha⁻¹ day⁻¹ in gliricidia-maize. We concluded that gliricidia-maize intercropping system could sequester more C in the soil than sole-maize.     

Life-cycle environmental and economic impacts of energy-crop fuel-chains: an integrated assessment of potential GHG avoidance in Ireland

This paper combines life-cycle analyses and economic analyses for Miscanthus and willow heat and electricity fuel-chains in Ireland. Displaced agricultural land-uses and conventional fuels were considered in fuel-chain permutations. Avoided greenhouse gas (GHG) emissions ranged from 7.7 to 35.2 t CO₂ eq. ha⁻¹ a⁻¹. Most fuel-chain permutations exhibited positive discounted financial returns, despite losses for particular entities at a farm-gate processed-biomass price of €100 t⁻¹ dry-matter. Attributing a value of €10 t⁻¹ CO₂ eq. to avoided GHG emissions, but subtracting financial returns associated with displaced fuel supplies, resulted in discounted annual national economic benefits (DANEBs) ranging from −457 to 1887€ ha⁻¹ a⁻¹. Extrapolating a plausible combination of fuel-chains up to a national indicative scenario resulted in GHG emission avoidance of 3.56 Mt CO₂ eq. a⁻¹ (5.2% of national emissions), a DANEB of 167 M€, and required 4.6% of national agricultural land area. As cost-effective national GHG avoidance options, Miscanthus and willow fuel-chains are robust to variation in yields and CO₂ price, and appear to represent an efficient land-use option (e.g. compared with liquid biofuel production). Policies promoting utilisation of these energy-crops could avoid unnecessary, and environmentally questionable, future purchase of carbon credits, as currently required for national Kyoto compliance.     

Response of “Alamo” switchgrass tissue chemistry and biomass to nitrogen fertilization in West Tennessee,USA

Switchgrass (Panicum virgatum) is a perennial, warm-season grass that has been identified as a potential biofuel feedstock over a large part of North America. We examined above- and belowground responses to nitrogen fertilization in “Alamo” switchgrass grown in West Tennessee, USA. The fertilizer study included a spring and fall sampling of 5-year old switchgrass grown under annual applications of 0, 67, and 202 kg N ha^?1 (as ammonium nitrate). Fertilization changed switchgrass biomass allocation as indicated by root:shoot ratios. End-of-growing season root:shoot ratios (mean ± SE) declined significantly (P ≤ 0.05) at the highest fertilizer nitrogen treatment (2.16 ± 0.08, 2.02 ± 0.18, and 0.88 ± 0.14, respectively, at 0, 67, and 202 kg N ha^?1). Fertilization also significantly increased above- and belowground nitrogen concentrations and decreased plant C:N ratios. Data are presented for coarse live roots, fine live roots, coarse dead roots, fine dead roots, and rhizomes. At the end of the growing season, there was more carbon and nitrogen stored in belowground biomass than aboveground biomass. Fertilization impacted switchgrass tissue chemistry and biomass allocation in ways that potentially impact soil carbon cycle processes and soil carbon storage.     

Market-based approaches and tools for improving water and air quality

Nitrogen (N) losses from agriculture are negatively impacting groundwater, air, and surface water quality. National, state, and local policies and procedures that can mitigate these problems are needed. Market-based approaches where waste treatment plants (point sources) can purchase nutrient credits from upstream agricultural operations (non-point sources) to meet their National Pollutant Discharge Elimination System permit requirements within the Clean Water Act are being explored. This paper reviews these market-based approaches for enhancing air and water quality at a lower cost than simple command-and-control regulation, and describes new tools that are being developed, such as Nitrogen Trading Tool (NTT), that can be used to assess nitrogen losses to the environment under different management scenarios. The USDA-NRCS, EPA and several other state and local agencies are interested in these new tools. The NTT, though primarily designed for water quality markets, also estimates savings in nitrous oxide (N₂O) emissions that can be traded in carbon markets. For example, an analysis using NTT shows that for 100 ha of crop land, a C sequestration equivalent of approximately 25–38 Mg C y^?1 for a farm in Ohio, and 13–21 Mg C y^?1 for a farm in Virginia could be achieved with better nitrogen management practices. These numbers across a watershed could be much larger with improved N and conservation management practices that contribute to better water quality and lower global warming potential. There is a need to further develop, calibrate, and validate these tools to facilitate nitrogen and carbon trading future markets around the globe to increase environmental conservation across agro-ecosystems worldwide.     

Linking spatio-temporal variation of crop response with sediment deposition along paddy rice terraces

In tropical mountainous regions of South East Asia, intensive cultivation of annual crops on steep slopes makes the area prone to erosion resulting in decreasing soil fertility. Sediment deposition in the valleys, however, can enhance soil fertility, depending on the quality of the sediments, and influence crop productivity. The aim of the study was to assess (i) the spatio-temporal variation in grain yield along two rice terrace cascades in the uplands of northern Viet Nam, (ii) possible linkage of sediment deposition with the observed variation in grain yield, and (iii) whether spatial variation in soil water or nitrogen availability influenced the obtained yields masking the effect of inherent soil fertility using carbon isotope (¹³C) discrimination and ¹⁵N natural abundance techniques. In order to evaluate the impact of seasonal conditions, fertilizer use and sediment quality on rice performance, ¹⁵N and ¹³C stable isotope compositions of rice leaves and grains taken after harvest were examined and combined with soil fertility information and rice performance using multivariate statistics. The observed grain yields for the non-fertilized fields, averaged over both cascades, accounted for 4.0 ± 1.4 Mg ha^?1 and 6.6 ± 2.5 Mg ha^?1 in the spring and summer crop, respectively, while for the fertilized fields, grain yields of 6.5 ± 2.1 Mg ha^?1 and 6.9 ± 2.1 Mg ha^?1 were obtained. In general, the spatial variation of rice grain yield was strongly and significantly linked to sediment induced soil fertility and textural changes, such as soil organic carbon (r 0.34/0.77 for Cascades 1 and 2, respectively) and sand fraction (r ?0.88/?0.34). However, the observed seasonal alteration in topsoil quality, due to sediment deposition over two cropping cycles, was not sufficient to fully account for spatial variability in rice productivity. Spatial variability in soil water availability, assessed through ¹³C discrimination, was mainly present in the spring crop and was linearly related to the distance from the irrigation channel, and overshadowed in Cascade 2 the expected yield trends based on sediment deposition. Although δ¹⁵N signatures in plants indicated sufficient N uptake, grain yields were not found to be always significantly influenced by fertilizer application. These results showed the importance of integrating sediment enrichment in paddy fields within soil fertility analysis. Furthermore, where the effect of inherent soil fertility on rice productivity is masked by soil water or nitrogen availability, the use of ¹³C and ¹⁵N stable isotopes and its integration with conventional techniques showed potential to enhance the understanding of the influence of erosion – sedimentation and nutrient fluxes on crop productivity, at toposequence level.