Energy balance and greenhouse gas emissions in organic and conventional avocado orchards in Mexico

There is a worldwide growing awareness of the negative impacts of the increasing fossil fuel reliance and greenhouse gas (GHG) emissions from agriculture, in particular for intensive crop systems. We analyze the energy balances and greenhouse gas emissions from export-oriented avocado orchards in Mexico. Avocado is a very important export crop and one of the main drivers of land-use change in the country. We compared 12 avocado orchards under organic and conventional management during two production cycles (2010 and 2011) in a representative region of Central Mexico. Our analysis shows no significant differences in energy consumption and GHG emissions between organic and conventional systems with 55 and 56 GJ ha⁻¹, and 3.30 t CO₂ equiv. ha⁻¹ and 3.57 t CO₂ equiv. ha⁻¹, respectively.Organic systems show three times more use of renewable energy than their conventional counterparts. However both systems depend heavily on fossil fuel inputs, machinery and N-fertilizers (synthetic or organic). Also, there is a high heterogeneity in management practices and input application within both systems, which is reflected in a large variation of their energy-related parameters. Given that avocado production is rapidly expanding in Mexico, a move toward organic production without systematically changing toward less fossil fuel dependent agricultural practices would not be sufficient to ensure a sustainable production.     

Biogas from dedicated energy crops in Northern Italy: electric energy generation costs

Agricultural anaerobic digestion facilities are increasing in many EU member States and biomass supply is sometimes an issue. Dedicated energy crops (DEC) (mainly Maize, Triticale and Sorghum) are often used to integrate other substrates, such as agricultural residues, manure and organic waste. However, DEC production includes onerous agricultural operations (soil preparation, harvest, transport and storage) and may result in high unit costs (UC) of electric energy (EE, € kWhe⁻¹), compared to other renewable sources. In this work, seven different types of DEC (4 different combinations of crop successions) were cultivated in 30 different parcels, distributed along the Po Valley (northern Italy), using different varieties of seeds for each crop type. All agricultural operations were accounted for their costs (988–3346 € ha⁻¹). Biomass production was measured and reported as average of different parcels for each type of crop (31.2–187 Mg ha⁻¹). Biomass dry matter content and biogas potential were measured on representative samples and the EE obtainable was calculated (7.9–35.3 MWhe ha⁻¹), by assuming conservative factors (CH₄ contents in biogas and electric generation yields). The costs of ensiled biomass sensibly varied (13.8–40 € Mg⁻¹) among crop solutions, as well as the same UC of EE (0.068–0.150 € kWhe⁻¹). These costs were considered together with typical plant management and investment costs (plant size: 0.5–1 MWe): total UC of EE generation through anaerobic digestion (considering 100% DEC) varied in a relatively wide range (0.143–0.279 € kWhe⁻¹). When the biomass mix is ‘blended’ with low-cost residues or organic waste, this range could be lowered to 0.096–187 € kWhe⁻¹. Only this strategy and strong efforts in reducing technological investment/management costs can candidate biogas-based EE as a really competitive renewable alternative to traditional sources, in the next future.     

Household energy and recycling of nutrients and carbon to the soil in integrated crop‐livestock farming systems: a case study in Kumbursa village,Central Highlands of Ethiopia

Soil amendment with organic wastes in the Highlands of Ethiopia has been greatly reduced by widespread use of dung cakes and crop residues as fuels. This study assessed the interaction between household energy and recycling of nutrients and carbon to the soil using household survey, focus group discussions, key informant interviews, direct observations and measurements between 2014 and 2015 in Kumbursa village (Central Highlands of Ethiopia). All surveyed households were entirely dependent on biomass fuel for cooking, with production and consumption rates directly related to wealth status, which significantly varied (P < 0.001) among three farm wealth groups (poor, medium and rich). Crop residues and dung cakes accounted for 80(±3)% by energy content and 85(±4)% by dry mass weight of total biomass fuel consumption. Mean losses were 59(±2) kg ha^?1 yr^?1 nitrogen (109(±8) kg yr^?1 per household), 13.9(±0.3) kg ha^?1 yr^?1 phosphorus (26(±2) kg yr^?1 per household), 79(±2) kg ha^?1 yr^?1 potassium (150(±11) kg yr^?1 per household) and 2100(±40) kg ha^?1 yr^?1 organic carbon (3000(±300) kg yr^?1 per household). Rich farmers lost significantly more carbon and nutrients in fuel than farmers in other wealth groups. However, these losses were spread over a larger area, so losses per land area were significantly higher for medium and poor than for rich farmers. This means that the land of poorer farmers is likely to become degraded more rapidly due to fuel limitations than that of rich farmers, so increasing the poverty gap. The estimated financial loss per household due to not using dung and crop residues as organic fertilizer was 162(±8) USSoil amendment with organic wastes in the Highlands of Ethiopia has been greatly reduced by widespread use of dung cakes and crop residues as fuels. This study assessed the interaction between household energy and recycling of nutrients and carbon to the soil using household survey, focus group discussions, key informant interviews, direct observations and measurements between 2014 and 2015 in Kumbursa village (Central Highlands of Ethiopia). All surveyed households were entirely dependent on biomass fuel for cooking, with production and consumption rates directly related to wealth status, which significantly varied (P < 0.001) among three farm wealth groups (poor, medium and rich). Crop residues and dung cakes accounted for 80(±3)% by energy content and 85(±4)% by dry mass weight of total biomass fuel consumption. Mean losses were 59(±2) kg ha^?1 yr^?1 nitrogen (109(±8) kg yr^?1 per household), 13.9(±0.3) kg ha^?1 yr^?1 phosphorus (26(±2) kg yr^?1 per household), 79(±2) kg ha^?1 yr^?1 potassium (150(±11) kg yr^?1 per household) and 2100(±40) kg ha^?1 yr^?1 organic carbon (3000(±300) kg yr^?1 per household). Rich farmers lost significantly more carbon and nutrients in fuel than farmers in other wealth groups. However, these losses were spread over a larger area, so losses per land area were significantly higher for medium and poor than for rich farmers. This means that the land of poorer farmers is likely to become degraded more rapidly due to fuel limitations than that of rich farmers, so increasing the poverty gap. The estimated financial loss per household due to not using dung and crop residues as organic fertilizer was 162(±8) US$ yr^?1. However, this is less than their value as fuels, which was 490(±20) US$ yr^?1. Therefore, farmers will only be persuaded to use these valuable assets as soil improvers if an alternative, cheaper fuel source can be found.     

Estimating biomass and carbon mitigation of temperate coniferous forests using spectral modeling and field inventory data

Realizing the importance of forest carbon monitoring and reporting in climate change, the present study was conducted to derive spectrally modeled aboveground biomass and mitigation using Landsat data in combination with sampled field inventory data in the coniferous forests of Western Himalaya. After conducting preliminary survey in 2009, 90 quadrats (45 each for calibration and validation) of 0.1 ha were laid in six forest types for recording field inventory data viz. diameter at breast height, height, slope and aspect. Biomass carbon (Mg ha^− 1) was worked out for different forest types and crown density classes (open with 10–40% crown density and closed with > 40% crown density) using recommended volume equations, ratios and factors. Biomass carbon map (aboveground + belowground) was generated for the entire region using geospatial techniques. Normalized difference vegetation index (NDVI) was generated and spectral values were extracted to establish relation (R² = 0.72, p < 0.01) with the field inventory data. The model developed was validated (R² = 0.73, p < 0.01) with 45 sample observations not used earlier for predicting and generating biomass carbon map (2009) for the entire region. The data from field based inventory indicates highest total biomass carbon (171.40, σ ± 23.19) Mg ha^− 1 for Fir–Spruce (closed) which has relatively more mature girth classes and low tree density. This value was found to be significantly higher than other forest types. Lowest biomass carbon was observed for Blue Pine (open) (37.15, σ ± 11.82) Mg ha^− 1. The NDVI values for the entire region ranged from 0 to 0.62 and consequently the spectrally derived aboveground biomass carbon varied from 0 to 600 Mg ha^− 1. The study demonstrates the application of mapping, spectral responses and sampled field inventory for type wise assessment of carbon mitigation in temperate coniferous forests of Himalayas.     

Regulation of Nitrogen Metabolism,Photosynthetic Activity,and Yield Attributes of Spring Wheat by Nitrogen Fertilizer in the Semi-arid Loess Plateau Region

It is critical for spring wheat (Triticum aestivum L.) production in the semi-arid Loess Plateau to understand the impact of nitrogen (N) fertilizer on changes in N metabolism, photosynthetic parameters, and their relationship with grain yield and quality. The photosynthetic capacity of flag leaves, dry matter accumulation, and N metabolite enzyme activities from anthesis to maturity were studied on a long-term fertilization trial under different N rates [0 kg ha^?1(N1), 52.5 kg ha^?1 (N2), 105 kg ha^?1 (N3), 157.5 kg ha^?1 (N4), and 210 kg ha^?1 (N5)]. It was observed that N3 produced optimum total dry matter (5407 kg ha^?1), 1000 grain weight (39.7 g), grain yield (2.64 t ha^?1), and protein content (13.97%). Our results showed that N fertilization significantly increased photosynthetic parameters and N metabolite enzymes at all growth stages. Nitrogen harvest index, partial productivity factor, agronomic recovery efficiency, and nitrogen agronomic efficiency were decreased with increased N. Higher N rates (N3–N5) maintained higher photosynthetic capacity and dry matter accumulation and lower intercellular CO₂ content. The N supply influenced NUE by improving photosynthetic properties. The N3 produced highest chlorophyll content, photosynthetic rate, stomatal conductance and transpiration rate, grain yield, grain protein, dry matter, grains weight, and N metabolite enzyme activities compared to the other rates (N1, N2, N4, and N5). Therefore, increasing N rates beyond the optimum quantity only promotes vegetative development and results in lower yields.

     

Snow cover manipulation in agricultural fields: as an option for mitigating greenhouse gas emissions

Short-term N₂O emission occurs in relation to snowmelt within seasonally frozen soil. To understand the effects of changing winter climates on the N₂O flux, snow cover manipulation experiments are useful. In Japan, snow cover manipulation is practiced by farmers to improve agricultural yield and is executed either by applying a broadcast of blackish agent onto the snow cover, which leads to faster snow-melting thereby extending the crop-growing season, or by snow cover removal/re-accumulation, leading to an enhanced soil frost depth for weed management. Implementation of these practices involves using an amount of fossil fuel, in addition to influencing soil-derived N₂O emissions, therefore, the load factors of snow cover management practices per unit area of agricultural field were estimated in this study. Field data including micrometeorological conditions, ground surface flux of N₂O, and amount of fossil fuel consumed during machinery operation for management practices, were obtained at two sites in Hokkaido over 2 years (2008–2010). Fuel consumption for the field spreading was found to be unexpectedly small (0.017 Mg CO₂ eq ha^?1). It was therefore suggested that acceleration of snowmelt may have the potential to reduce net greenhouse gas emissions if the agent used is a low-degradable C-rich material, such as charcoal. For soil frost control, the fossil fuel consumption during a set of snow cover removal/re-accumulation (estimated as 0.052 Mg CO₂ eq ha^?1) is discussed, together with the relationship between possible mechanisms causing stimulation of N₂O production in frozen soil and inherent large differences in N₂O flux among sites.     

Seed and leaf-spray inoculation of PGPR in brachiarias (Urochloa spp.) as an economic and environmental opportunity to improve plant growth,forage yield and nutrient status

Purpose

Brazil has 180 Mha of pastures, 86 Mha occupied with Urochloa spp. (syn. Brachiaria), and 70% in some level of degradation. Inoculation with plant-growth-promoting bacteria (PGPR) may represent an economic and environmental feasible strategy to improve pasture production.

Methods

Two greenhouse and seven field trials were performed to verify the effects of seed inoculation at sowing or leaf-spray inoculation in established pastures of Urochloa with elite strains of Azospirillum brasilense and Pseudomonas fluorescens. All plants received nutrients including 40 kg ha^?1 of N at sowing, and half of the treatments a supply of 40 kg ha^?1 of N 30 days after emergence.

Results

A. brasilense increased shoot biomass by an average of 16.8% with both seed and leaf-spray inoculation, whereas P. fluorescens increased by 15.2 and 14.2%, respectively, always higher with the extra supply of N. Seed and leaf-spray inoculation with A. brasilense increased N content by an average of 11.7 and 20.7%, and K by 9.9 and 11.3%, respectively; for P. fluorescens average increases were of 33.3 and 36.6% for P, and of 10.6 and 13.6% for K, respectively. Benefits were mainly attributed to improvements in root architecture by the synthesis of phytohormones. Biological nitrogen fixation in A. brasilense, P acquisition (solubilization of phosphates and siderophores synthesis) and ACC-deaminase in P. fluorescens also contributed to plant growth and nutrient status.

Conclusion

Inoculation with elite PGPR strains translated into more fodder and improved nutritional value of feed for livestock, representing a promising and environmentally-friendly strategy for tropical pastures.

     

Life cycle assessment of winter road maintenance

Purpose

Winter road maintenance in the Nordic climate is demanding due to challenging weather conditions, high precipitation, and icy conditions. As a leading country in the transition to low-emission transport, Norway must work to reduce their emissions while providing a safe level of service through winter maintenance operations. This article investigates the environmental impacts of winter road maintenance (WRM) in Norway both today and under a climate change scenario predicted for 2050.

Methods

Life cycle assessment (LCA) is used to evaluate the environmental impact of the functional unit “average winter road maintenance in Norway on national and county roads per km.lane.” The ReCiPe (hierarchy) method was used to identify and categorize emissions related to WRM to show how different factors affect the system and to reveal hidden emissions hotspots. Real-time data from WRM vehicles were used to determine how fuel consumption is affected by gradient and weather. Producers and operators provided other relevant information on WRM vehicles. Official reports supplied information on deicer quantities used and the total distance driven by WRM vehicles in Norway.

Results and discussion

The quantity of deicer used is the main source of emissions contributing toward all impact categories. The effect of deicer is likely to be even higher in certain impact categories. The environmental impact of the deicer after application is not included. The representation of WRM in existing emissions data is limited despite the considerable amount of deicer applied and the long distances that WRM vehicles travel. The results document how energy use throughout the system is another important source of emissions. Various parameters, such as road gradient, vehicle properties, driver behavior, and weather, affect the fuel consumption of WRM vehicles, with weather being the most important of these.

Conclusions

Significant potential for emissions reductions from WRM was found, and WRM operations should be included in cold-climate road LCA studies. The environmental impacts of deicer application are especially high compared to the mechanical clearing of roads and contribute strongly to impact categories such as terrestrial, freshwater, and human toxicity and to the formation of particulate matter.

     

Environmental and techno-economic analyses of bio-jet fuel produced from jatropha and castor oilseeds in China

Purpose

Bio-jet fuel derived from energy crops has been promoted by governments around the world through policies such as the Carbon Offsetting and Reduction Scheme for International Aviation. The environmental impact and techno-economic analysis of bio-jet fuel are particularly pertinent to China because China is under huge pressure to reduce emissions, endeavouring to meet bio-economic goals.

Methods

An LCA study was conducted on the production of bio-jet fuel from jatropha and castor by estimating the well-to-wake emissions and its economic impact. The functional unit was 1 MJ of bio-jet fuel, and field survey data was used in inventory analysis. A scenario analysis was performed to measure diverse conditions, including the planting conditions, planting regions, allocation methods, and hydrogen sources. A techno-economic analysis that combined the production costs and co-product credits was performed to calculate the minimum bio-jet fuel selling price (MJSP) based on a plant capacity of 2400 metric tonnes of feedstock per day.

Results and discussion

Compared to the environmental impacts to the fossil jet fuel, the use of biofuel would reduce the majority environmental impacts by 36–85%, when a 1:1 displacement of fossil jet fuel is considered, though the human toxicity potential impact was 100% higher. The scenario analysis indicated that (i) planting castor in harsh and unevenly distributed conditions and jatropha in stable or fertile conditions can leverage their respective advantage; (ii) the global warming potential (GWP) from castor planting in the region of north-east China ranges from 34 to 48 g CO₂ eq/MJ; (iii) the GWP produced through the steam methane reforming process can be reduced by 16–17%, using advances in technological processes. The MJSP for fuel produced from jatropha and castor under the basic scenario is estimated to be 5.68 and 4.66 CNY/kg, respectively, which falls within the current market price range of 4.5–7.5 CNY/kg.

Conclusions

Bio-jet fuel from jatropha and castor oilseeds offers potential environmental benefits if they can reduce fossil jet fuel on an energy-equivalent basis. However, these benefits are likely to be reduced by the rebound effect of the fuel market. Future research is needed to better understand the magnitude of the rebound effect in China and what policy interventions can be implemented to alleviate it. Scenario analysis demonstrated the feasibility and potential of bio-jet fuel development from multiple perspectives and technological progress are conducive to the realization of environmental protection policies.

     

Commercial experience with miscanthus crops: Establishment,yields and environmental observations

This study investigates the condition of commercial miscanthus fields, growers’ concerns and reasons for growing the crop and also the modelling of a realistic commercial yield. Juvenile and mature Miscanthus × giganteus crops of varying age are surveyed in growers’ fields across mid‐England. We record in‐field plant density counts and the morphology of crops of different ages. Mature crops thrive on both clay and sandy soils. Plants surveyed appear robust to drought, weeds and disease, the only vulnerability is rhizome condition when planting. Mature miscanthus planted pre‐2014 continues to develop, spreading into planting gaps and growing more tillers. In stands planted post‐2014, improved planting techniques reduce planting gaps and create a reasonably consistent planting density of 12,500 plants/ha. The main reason for growers' investment in miscanthus is not financial return, but relates to its low requirement for field operations, low maintenance cost and regeneration. This offers practical solutions for difficult field access and social acceptability near public places (related to spray operations and crop vandalism). Wildlife is abundant in these fields, largely undisturbed except for harvest. This contributes to the greening of agriculture; fields are also used for gamebird cover and educational tours. This crop is solving practical problems for growers while improving the environment. Observed yield data indicate gradual yield increase with crop age, a yield plateau but no yield decrease since 2006. In stands with low planting densities, yields plateau after 9 years. Surveyed yield data are used to parameterize the MiscanFor bioenergy model. This produces options to simulate either juvenile yields or a yield for a landscape containing different aged crops. For mature English crop yields of 12 t ha^?1 year^?1, second‐ and third‐year juvenile harvests average 7 t ha^?1 year^?1 and a surrounding 10 km by 10 km area of distributed crop age would average 9 t ha^?1 year^?1.     

Improvement of growth,under field conditions,of wheat inoculated with <Emphasis Type="Italic">Pseudomonas chlororaphis</Emphasis> subsp.<Emphasis Type="Italic"> aurantiaca</Emphasis> SR1

Effects of inoculation of wheat (Triticum aestivum L.) with the rhizobacterium Pseudomonas chlororaphis subsp. aurantiaca strain SR1 (termed SR1) were studied at an experimental field site in Río Cuarto, Argentina. Treatments involved SR1 inoculation with or without nitrogen/phosphorus fertilization. Inoculation produced a significant increase in plant height and root length in early growth stages. Inoculation plus fertilization with 40 kg ha⁻¹ urea/30 kg ha⁻¹ diamonic phosphate (“50% dose”) gave a yield increase of 636 kg ha⁻¹ relative to control, and an increase of 472 kg ha⁻¹ relative to fertilization with 80 kg ha⁻¹ urea/60 kg ha⁻¹ phosphate without inoculation. SR1 inoculation without fertilization, compared to control, produced increases of 6% in weight of 1,000 grains, 13% in number of spikes per plant, and 30% in number of grains per spike. Inoculation plus 50% dose fertilization also improved these parameters. Results of the study indicate that inoculation of wheat with SR1 improves various growth and yield parameters, and allows reduced dosage of nitrogen/phosphorus fertilizers in the field.     

Evaluation of carbon accrual in afforested agricultural soils

Afforestation of agricultural lands can provide economically and environmentally realistic C storage to mitigate for elevated CO₂ until other actions such as reduced fossil fuel use can be taken. Soil carbon sequestration following afforestation of agricultural land ranges from losses to substantial annual gains. The present understanding of the controlling factors is inadequate for understanding ecosystem dynamics, modeling global change and for policy decision‐makers. Our study found that planting agricultural soils to deciduous forests resulted in ecosystem C accumulations of 2.4 Mg C ha⁻¹ yr⁻¹ and soil accumulations of 0.35 Mg C ha⁻¹ yr⁻¹. Planting to conifers showed an average ecosystem sequestration of 2.5 and 0.26 Mg C ha⁻¹ yr⁻¹ in the soils but showed greater field to field variability than when planted to deciduous forest. Path analysis showed that Ca was positively related to soil C accumulations for both conifers and deciduous afforested sites and played a significant role in soil C accumulations in these sites. Soil N increases were closely related to C accumulation and were two times greater than could be explained by system N inputs from atmospheric deposition and natural sources. Our results suggest that the addition of Ca to afforested sites, especially conifers, may be an economical means to enhance soil C sequestration even if it does not result in increasing C in aboveground pools. The mechanism of N accumulation in these aggrading stands needs further investigation.     

A new methodological approach to the establishment of sustainable agricultural ecology in drought vulnerable areas of eastern India

Rice (Oryza sativa L.), the staple food for much of the world, requires gallons of water during its growth phase from tillage to harvest through conventional farming and emits significant greenhouse gases. Hence, modified cultivation techniques are felt to be needed to increase rice productivity, minimize water and fertilizer consumption effectively, and mitigate greenhouse gas emissions to a certain extent. The present experiment was based on the Purulia district, identified as a drought-prone zone through the RS-GIS technique. Two methods, the conventional method (CVN) and the system of rice intensification (SRI), were studied with four varieties of rice, viz. var. MTU 1010, var. IET 4786, var. IET 17430 and var. IET 9947 on water resource vulnerability, associated greenhouse gas emissions (CH₄, N₂O) and global warming potential (GWP). The results indicated that SRI cultivation is the smart method compared to CVN in the drought-prone Purulia District due to its lower water requirements and greenhouse gas (GHG) emissions. There was higher CH₄ flux among the CVN plots than in the SRI plots (p < 0.05). The N₂O flux in the rice field plots of CVN (Rabi-1.54 ± 0.04 kg ha⁻¹, Kharif 1.51 ± 0.10 kg ha⁻¹) was lower than the SRI (Rabi-2.08 ± 0.07, Kharif- 1.83 ± 0.02 kg ha⁻¹) during Rabi season. The CH₄ flux for CVN (Rabi-94.32 ± 2.71 kg ha⁻¹; Kharif 110.33 ± 3.90 kg ha⁻¹) was higher than the SRI (Rabi-68.16 ± 2.37, Kharif- 61.72 ± 2.41 kg ha⁻¹) during Rabi season. The CO₂-eq emission (pGWP) and yield-scaled CO₂-eq emission (YpGWP) from the SRI were significantly lower when compared with CVN (p < 0.05). The result shows that the SRI technique is an effective agricultural method that farmers should be encouraged to follow in the drought-prone region to ensure less water consumption and a sustainable future for generations.     

Freight transport in the context of industrial ecology and sustainability: evaluation of uni- and multi-modality scenarios via life cycle assessment

Purpose

This study aims at comparing, from an environmental point of view, four different scenarios of freight transport at the Italian level, on an equal base of route between supplier and customer. The first scenario included freight movements by truck and mainly ship, the second included track and mainly train, the third was the three-modal based scenario, whilst the fourth scenario was the only uni-modal, based only upon truck movement.

The study was conducted to find the environmentally sustainable solution, or at least a sustainable trade-off, as well as the most environmentally burdening issues, associated with the geographic dimension of transport in Italy, towards sustainability.

Methods

Using uni‐ and multi-modal freight movements by truck, rail and ship, a life cycle assessment (LCA) was developed to estimate the related environmental burdens both at the midpoint and at the endpoint levels from the consumption of primary energy and natural resources along with the emissions of greenhouse gases (GHGs) and of other pollutants. Primary data were compiled as part of the inventory analysis and consisted in the transport flows associated with the system investigated: those were calculated from the distance travelled and the goods load transported. Primary data were then combined with secondary data that were modelled with the transport life cycle modules contained in Ecoinvent: from those modules, the fuel consumption amounts associated transport flows were extrapolated, and used for the assessment.

Results

Results showed that the environmental impact of the multi-modal scenarios is lower compared with the uni-modal scenario. The best performing option was found to be the third scenario providing use of all the three freight means, namely ship, train and truck. However, this scenario is not being practiced for several reasons, mainly due to control and monitoring difficulties of each step and higher operational costs. The first and second scenarios showed a quite comparable environmental behaviour and so are to be considered as viable options.

Conclusions

Apart from highlighting the most environmentally viable transport options, the study contributed to finding the indicators of environmental impact and damage that best describe the system investigated and are recommended by this author team to be accounted for in future assessments in the transport sector. Finally, although site-specific, the results of this study may be useful to logistics companies, policy and decision makers of other regions and countries towards identifying and promoting environmentally optimal freight transport solutions, contributing to sustainability of the transport sector.

     

Energy and carbon accounting to compare bioenergy crops

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Highlights► Comparing biofuel crops is exceedingly difficult using conventional measurement methods. ► The PETRO approach quantitatively compares biological matter in terms of energy and carbon. ► Tracking carbon flux from air to liquid fuel compares all biofuel crop yields on a common basis. ► Reporting energy yields (GJ ha⁻¹ y⁻¹) and carbon flux (Mg_C ha⁻¹ y⁻¹) enables regional comparison.     

Positive legacy effect of previous legume proportion in a ley on the performance of a following crop of Lolium multiflorum

Aims

We investigated the legacy effects of a previous ley’s legume proportion on the performance of a following grass crop in a rotation.

Methods

In April 2015, a pure Lolium multiflorum L. crop was sown after the removal of legume containing swards (0–100% legumes), and was harvested four times over the following one-year period (3 times in 2015 and once the following April 2016). Labeled ¹⁵N fertilizer (50 kg N ha⁻¹) was applied during the 2nd and 3rd re-growth periods to determine N fluxes.

Results

Across the one-year period, a significant legume-legacy induced increase in biomass yield of L. multiflorum was observed over the entire range of previous legume proportions when compared against the non-legume ley, the effect being 2.15 and 1.73 t ha⁻¹ (P ≤ 0.001 each) in swards with 50% and 100% previous legume proportion, respectively, or up to +31%. The legume-legacy effect on biomass yield was most pronounced at the 1st harvest (June) and persisted into the 2nd harvest in August (P ≤ 0.05 both, over the entire range of previous legume proportion), though was no longer evident at the 3rd harvest (September). Importantly, the legume-legacy effect returned in the 4th harvest in April (P ≤ 0.05). Examining the source of N contributing to N yield confirmed that more N was derived from the soil at harvest 1 and 2 for previous legume containing leys (P ≤ 0.001) compared to those which contained no legumes, with a significant increase still seen for legume mixtures at harvest 3 (P ≤ 0.01).

Conclusions

The results demonstrate a sustained soil-transferred performance-enhancing legacy effect on a following crop in a rotation, with previous legume proportions of 50% having a comparable effect compared with that of a previous legume monoculture.

     

Quantitative classification and carbon density of the forest vegetation in Lüliang Mountains of China

Forests play a major role in global carbon (C) cycle, and the carbon density (CD) could reflect its ecological function of C sequestration. Study on the CD of different forest types on a community scale is crucial to characterize in depth the capacity of forest C sequestration. In this study, based on the forest inventory data of 168 field plots in the study area (E 111°30′–113°50′, N 37°30′–39°40′), the forest vegetation was classified by using quantitative method (TWINSPAN); the living biomass of trees was estimated using the volume-derived method; the CD of different forest types was estimated from the biomass of their tree species; and the effects of biotic and abiotic factors on CD were studied using a multiple linear regression analysis. The results show that the forest vegetation in this region could be classified into 9 forest formations. The average CD of the 9 forest formations was 32.09 Mg ha⁻¹ in 2000 and 33.86 Mg ha⁻¹ in 2005. Form. Picea meyeri had the highest CD (56.48 Mg ha⁻¹), and Form. Quercus liaotungensis + Acer mono had the lowest CD (16.14 Mg ha⁻¹). Pre-mature forests and mature forests were very important stages in C sequestration among four age classes in these formations. Forest densities, average age of forest stand, and elevation had positive relationships with forest CD, while slope location had negative correlation with forest CD.     

Decomposition rates and nutrient dynamics of Picea abies needles,twigs and fine roots after stem-only harvesting in eastern and western Norway

Objectives

Afforestation changes soil chemical properties over several decades. In contrast, microbial community structure can be shifted within the first decade and so, the direct effects of tree species can be revealed. The aim of this study was to determine the alteration of soil microbial community composition 10 years after afforestation by trees with contrasting functional traits.

Methods

The study was conducted at the BangorDIVERSE temperate forest experiment. Soil samples were collected under single, two and three species mixtures of alder and birch, beech and oak - early and secondary successional species, respectively, and contiguous agricultural field. Soil was analysed for total carbon (C) and nitrogen (N) contents, and microbial community structure (phospholipid fatty acids (PLFAs) analysis).

Results and conclusions

The total PLFAs content (370–640 nmol g^?1 soil) in forest plots increased for 30 to 110 % compared to the agricultural soil (290 nmol g^?1 soil). In contrast, soil C, N and C/N ratios were altered over 10 years much less - increased only up to 20 % or even decreased (for beech forest).

Afforestation increased bacterial PLFAs by 20–120 %, whereas it had stronger impact on the development of fungal communities (increased by 50–200 %). These effects were proved for all forests, but were more pronounced under the monocultures compared to mixtures. This indicates that species identity has a stronger effect than species diversity. Principal component analysis of PLFAs revealed that under mono and three species mixtures similar microbial communities were formed. In contrast, gram-positive PLFAs and actinomycete PLFAs contributed mainly to differentiation of two species mixtures from other forests. Thus, at the early afforestation stage: i) soil biological properties are altered more than chemical, and ii) tree species identity affects more than species amount on both processes.

     

Greenhouse gas mitigation potential in crop production with biochar soil amendment—a carbon footprint assessment for cross‐site field experiments from China

Biochar soil amendment (BSA) had been advocated as a promising approach to mitigate greenhouse gas (GHG) emissions in agriculture. However, the net GHG mitigation potential of BSA remained unquantified with regard to the manufacturing process and field application. Carbon footprint (CF) was employed to assess the mitigating potential of BSA by estimating all the direct and indirect GHG emissions in the full life cycles of crop production including production and field application of biochar. Data were obtained from 7 sites (4 sites for paddy rice production and 3 sites for maize production) under a single BSA at 20 t/ha^?1 across mainland China. Considering soil organic carbon (SOC) sequestration and GHG emission reduction from syngas recycling, BSA reduced the CFs by 20.37–41.29 t carbon dioxide equivalent ha^?1 (CO₂‐eq ha^?1) and 28.58–39.49 t CO₂‐eq ha^?1 for paddy rice and maize production, respectively, compared to no biochar application. Without considering SOC sequestration and syngas recycling, the net CF change by BSA was in a range of ?25.06 to 9.82 t CO₂‐eq ha^?1 and ?20.07 to 5.95 t CO₂‐eq ha^?1 for paddy rice and maize production, respectively, over no biochar application. As the largest contributors among the others, syngas recycling in the process of biochar manufacture contributed by 47% to total CF reductions under BSA for rice cultivation while SOC sequestration contributed by 57% for maize cultivation. There was a large variability of the CF reductions across the studied sites whether in paddy rice or maize production, due likely to the difference in GHG emission reductions and SOC increments under BSA across the sites. This study emphasized that SOC sequestration should be taken into account the CF calculation of BSA. Improved biochar manufacturing technique could achieve a remarkable carbon sink by recycling the biogas for traditional fossil‐fuel replacement.