• Authors:
    • Chatterton, J.
    • Graves, A.
    • Kulak, M.
  • Source: Landscape and Urban Planning
  • Volume: 111
  • Issue: March
  • Year: 2013
  • Summary: The production and supply of food currently accounts for 20-30% of greenhouse gas (GHG) emissions in the UK and the government and nongovernmental organisations are seeking to reduce these environmental burdens. Local authorities all over UK establish community farms with the aim to produce more sustainable food for citizens. This study used environmental Life Cycle Assessment (LCA) to quantify the potential savings of food-related GHG emissions that may be achieved with the establishment of an urban community farm, based on a case study recently found in the London Borough of Sutton. The work identified elements of the farm design that require the greatest attention to maximise these savings. The greatest reductions can be achieved by selecting the right crops: (i) providing the highest yields in local conditions and (ii) usually produced in energy-intensive greenhouses or air-freighted to UK from outside Europe. Implications from further development of the farm on the local, unused land were examined, taking into account market requirements. This showed that land used on an urban fringe for food production could potentially reduce greenhouse gas emissions in Sutton by up to 34 t CO(2)e ha(-1) a(-1). Although the percentage of this reduction in total diet emissions is relatively low, the result exceeds carbon sequestration rates for the conventional urban green space projects, such as parks and forests. (C) 2012 Elsevier B.V. All rights reserved.
  • Authors:
    • Shang, Z. H.
    • Chen, X. P.
    • Pan, J. L.
    • Dai, W. A.
    • Wang, X. M.
    • Ma, L. N.
    • Guo, R. Y.
  • Source: Chinese Journal of Eco-Agriculture
  • Volume: 21
  • Issue: 11
  • Year: 2013
  • Summary: Soil carbon and nitrogen in vegetable fields are the core elements of soil quality and environmental pollution. The decrease of soil C/N ratio of vegetable fields under greenhouse conditions causes an imbalance in soil carbon and nitrogen content. An effective way of adjusting soil carbon and nitrogen conditions in vegetable fields has been by improving soil quality and decreasing environmental pollution. Furthermore, there has been little research on soil carbon and nitrogen mineralization under greenhouse conditions in the Tibetan region. After transformations of alpine meadows and farmlands into solar greenhouse vegetable fields, there was the need to study the characteristics and processes of soil mineralization. In this study therefore, carbon and nitrogen mineralization in soils of alpine grassland, farmland and greenhouse (1-year, 5-year) were analyzed in an indoor incubation experiment. The results showed that soil carbon mineralization in different soil types mainly occurred during the first seven days (0-7 d) after treatment. Soil carbon mineralization was higher under alpine grassland than in farmland and 5-year greenhouse conditions ( P0.05). This was attributed to soil nutrient and soil microbial environment sensitivity to temperature. Soil CO 2-C accumulation in farmland soil was higher than in alpine grassland soil. It was also higher in alpine grassland soil than in the 1-year greenhouse and 5-year greenhouse soils. However, the differences in soil organic carbon mineralization and accumulation among alpine grassland, farmland, 1-year greenhouse and 5-year greenhouse soil conditions were not significant ( P>0.05) at 28 days after treatment. Soil nitrogen mineralization mainly happened in different soil types during the first three days (3 d) after treatment. With delayed incubation, the main process of soil nitrogen mineralization was nitrogen fixation. Soil inorganic nitrogen content in alpine grassland, farmland, 1-year greenhouse and 5-year greenhouse soils at 28 days after incubation were 29.04%, 75.94%, 66.86% and 65.70% of that at 0 day, respectively. The results showed that soil nitrogen mineralization capacity of alpine grassland soil was stronger than farmland, 1-year greenhouse and 5-year greenhouse soils. Soil nitrogen mineralization capacity of farmland was weaker than alpine grassland, 1-year greenhouse and 5-year greenhouse. Also soil nitrogen mineralization capacities of 1-year greenhouse and 5-year greenhouse were similar. Moreover, soil mineralization processes were similar among different soil conditions.
  • Authors:
    • Xie, D. T.
    • Shi, S.
    • Liu, Y. Y.
    • Li, J. Q.
    • Ni, J. P.
    • Huang, A. Y.
    • Mu, Z. J.
    • Hatano, R.
  • Source: Journal of Soil Science and Plant Nutrition
  • Volume: 13
  • Issue: 3
  • Year: 2013
  • Summary: Vegetable fields in China are characterized with intensive fertilization and cultivation, and their net effect on the global warming deserves attention. Greenhouse gas fluxes were thus measured, using a static closed chamber method, over approximately 18 months in two typical subtropical vegetable fields with different soil types and contrasting soil properties. Five consecutive crops were planted in one field and four in the other. Intensive fertilization consistently stimulated soil N2O emission, while imposed complicated impact on soil respiration with CO2 emission enhanced in one field and suppressed in the other field. The fertilizer-induced N2O emission factors (EFs) varied with individual crop phases and averaged 1.4 to 3.1% across the whole sampling period for different fields. The interaction of soil temperature and moisture could explain about 58% of the seasonal variation in the EFs. All the soils under different vegetable cropping systems were net sources of atmospheric radiative forcing and the net global warming potential over the entire study period ranged from 1,786 to 3,569 g CO2 equivalence m(-2) for fertilized soils with net CO2 emission contributing 53 to 67% and N2O emission occupying the remaining 33 to 47%.
  • Authors:
    • Salokhe, V. M.
    • Taewichit, C.
    • Soni, P.
  • Source: Agricultural Systems
  • Volume: 116
  • Year: 2013
  • Summary: Farm mechanization has been progressively increasing in Thailand for the past decades. Consumption and abuse of energy intensive inputs, machinery and agro-chemicals is increasingly propagated into agricultural production systems. Effects of energy intensive input utilization and farm technologies are directly associated especially with farm economic and atmospheric issues. This warrants the need of energy input-output analyses coupled with its environmental dimension. This paper presents the energy input-output analyses of different agricultural activities and fresh pond-culture (polyculture), for which data were collected from 46 rainfed integrated agricultural production systems (IAPSs) of 281 farm plots surveyed. Total energy consumption including non-renewable energy input (NREI), direct and indirect energy input, and system efficiency are calculated and compared for different crops. Resource-wise energy input utilization and energy consumed by farm operations are also discussed for different crops. Further, this study simultaneously relates energy consumption in agricultural production systems associated with their corresponding greenhouse gases (GHGs) emission - presented in terms of total carbon dioxide equivalent (CO(2)e). Results reveal noticeable variations in energy consumption and CO(2)e emissions from various agricultural production activities. The study reveals that the maximum energy consumer is cassava (32.4 GJ ha(-1)). Major energy input consumption for all productions are indicated by fossil fuel (diesel oil) as fresh pond-culture depended on fish feed. Transplanted rice provides the highest CO(2)e emission (1112 kg CO(2)e ha(-1)) among crops, in which more than 50% is contributed by methane (CH4).
  • Authors:
    • Suddick, E. C.
    • Six, J.
  • Source: Science of the Total Environment
  • Volume: 465
  • Year: 2013
  • Summary: Agricultural soils are responsible for emitting large quantities of nitrous oxide (N2O). The controlled incomplete thermal decomposition of agricultural wastes to produce biochar, once amended to soils, have been hypothesized to increase crop yield, improve soil quality and reduce N2O emissions. To estimate crop yields, soil quality parameters and N2O emissions following the incorporation of a high temperature (900 degrees C) walnut shell (HTWS) biochar into soil, a one year field campaign with four treatments (control (CONT), biochar (B), compost (COM), and biochar+compost (B+C)) was conducted in a small scale vegetable rotation system in Northern California. Crop yields from five crops (lettuce, winter cover crop, lettuce, bell pepper and Swiss chard) were determined; there were no significant differences in yield between treatments. Biochar amended soils had significant increases in % total carbon (C) and the retention of potassium (K) and calcium (Ca). Annual cumulative N2O fluxes were not significantly different between the four treatments with emissions ranging from 0.91 to 1.12 kg N2O-N ha(-1) yr(-1). Distinct peaks of N2O occurred upon the application of N fertilizers and the greatest mean emissions, ranging from 67.04 to 151.41 g N2O-N ha(-1) day(-1), were observed following the incorporation of the winter cover crop. In conclusion, HTWS biochar application to soils had a pronounced effect on the retention of exchangeable cations such as K and Ca compared to un-amended soils and composted soils, which in turn could reduce leaching of these plant available cations and could thus improve soils with poor nutrient retention. However, HTWS biochar additions to soil had neither a positive or negative effect on crop yield nor cumulative annual emissions of N2O.
  • Authors:
    • Shi,Tiezhu
    • Cui,Lijuan
    • Wang,Junjie
    • Fei,Teng
    • Chen,Yiyun
    • Wu,Guofeng
  • Source: Plant and Soil
  • Volume: 366
  • Issue: 1-2
  • Year: 2013
  • Summary: This study aimed to compare stepwise multiple linear regression (SMLR), partial least squares regression (PLSR) and support vector machine regression (SVMR) for estimating soil total nitrogen (TN) contents with laboratory visible/near-infrared reflectance (Vis/NIR) of selected coarse and heterogeneous soils. Moreover, the effects of the first (1st) vs. second (2nd) derivative of spectral reflectance and the importance wavelengths were explored. The TN contents and the Vis/NIR were measured in the laboratory. Several methods were employed for Vis/NIR data pre-processing. The SMLR, PLSR and SVMR models were calibrated and validated using independent datasets. Results showed that the SVMR and the PLSR models had similar performances, and better performances than the SMLR. The spectral bands near 1450, 1850, 2250, 2330 and 2430 nm in the PLSR model were important wavelengths. In addition, the 1st derivative was more appropriate than the 2nd derivative for spectral data pre-processing. PLSR was the most suitable method for estimating TN contents in this study. SVMR may be a promising technique, and its potential needs to be further explored. Moreover, the future studies using outdoor and airborne/satellite hyperspectral data for estimating TN content are necessary for testing the findings.
  • Authors:
    • Luna, J. M.
    • Mitchell, J. P.
    • Shrestha, A.
  • Source: Renewable Agriculture and Food Systems
  • Volume: 27
  • Issue: 1
  • Year: 2012
  • Summary: Organic farming has been historically dependent on conventional tillage operations to convert perennial pasture leys to annual crop rotations, incorporate crop residues, compost and cover crops, as well as to mechanically kill existing vegetation. Conventional tillage, however, has long been known to lead to soil degradation and erosion. A recently developed no-till organic production system that uses a roller-crimper technology to mechanically kill cover crops was evaluated in two states in the western United States. In Washington, pumpkins ( Cucurbita spp.) grown in a no-till roller-crimper (NT-RC) system produced yields 80% of conventional tillage, but with fewer weeds. However, in California on-farm research trials in organic cotton ( Gossypium barbadense L.), tomato ( Lycopersicon esculentum Mill.), eggplant ( Solanum melongena L.) and cowpea ( Vigna unguiculata (L.) Walp.), the no-till system produced virtual crop failure, or yields less than 20% of the standard production method. The major problems associated with rolled cover crops in California included reduced crop seedling emergence, planter impediment with excessive residue, lack of moisture and delay in transplanting of vegetable crops due to continued growth of cover crops, in-season crop competition from cover crop regrowth and impracticability of using cultivators. Further, excessive dry residue during summer in California can present the risk of fire. In both California and Oregon, considerable success has been demonstrated with zone tillage (strip tillage) in conventionally produced field and vegetable crops. In a replicated Oregon trial, the organic strip tillage treatment produced 85% of the broccoli ( Brassica oleracea L.) yield compared to a conventional tillage treatment. Our studies suggest that the zone tillage concept may offer opportunities to overcome many of the agronomic challenges facing no-till.
  • Authors:
    • Seufert, V.
    • Ramankutty, N.
    • Foley, J. A.
  • Source: Nature
  • Volume: 485
  • Issue: 7397
  • Year: 2012
  • Summary: Numerous reports have emphasized the need for major changes in the global food system: agriculture must meet the twin challenge of feeding a growing population, with rising demand for meat and high-calorie diets, while simultaneously minimizing its global environmental impacts. Organic farming - a system aimed at producing food with minimal harm to ecosystems, animals or humans - is often proposed as a solution. However, critics argue that organic agriculture may have lower yields and would therefore need more land to produce the same amount of food as conventional farms, resulting in more widespread deforestation and biodiversity loss, and thus undermining the environmental benefits of organic practices. Here we use a comprehensive meta-analysis to examine the relative yield performance of organic and conventional farming systems globally. Our analysis of available data shows that, overall, organic yields are typically lower than conventional yields. But these yield differences are highly contextual, depending on system and site characteristics, and range from 5% lower organic yields (rain-fed legumes and perennials on weak-acidic to weak-alkaline soils), 13% lower yields (when best organic practices are used), to 34% lower yields (when the conventional and organic systems are most comparable). Under certain conditions - that is, with good management practices, particular crop types and growing conditions - organic systems can thus nearly match conventional yields, whereas under others it at present cannot. To establish organic agriculture as an important tool in sustainable food production, the factors limiting organic yields need to be more fully understood, alongside assessments of the many social, environmental and economic benefits of organic farming systems.
  • Authors:
    • O'Donovan, J.
    • Harker, K.
    • Clayton, G.
    • Dosdall, L.
    • Hummel, J.
  • Source: Environmental Entomology
  • Volume: 41
  • Issue: 1
  • Year: 2012
  • Summary: Diversity and abundance of ground beetles (Coleoptera: Carabidae) can be enhanced in vegetable and field intercropping systems, but the complexity of polycultures precludes the application of generalized assumptions of effects for novel intercropping combinations. In a field experiment conducted at Lacombe and Ellerslie, Alberta, Canada, in 2005 and 2006, we investigated the effects of intercropping canola ( Brassica napus L.) with wheat ( Triticum aestivum L.) on the diversity and community structure of carabid beetles, and on the activity density responses of individual carabid species. Shannon-Wiener diversity index scores and species evenness increased significantly as the proportion of wheat comprising total crop plant populations increased in one site-year of the study, indicating a positive response to enhanced crop plant species evenness in the intercrops, and in that same site-year, ground beetle communities in intercrops shifted to more closely approximate those in wheat monocultures as the percentage of wheat in the intercrops increased. Individual carabid species activity densities showed differing responses to intercropping, although activity densities of some potential root maggot ( Delia spp.) (Diptera: Anthomyiidae) predators were greater in intercrops with high proportions of wheat than in canola monocultures. The activity density of Pterostichus melanarius (Illiger), the most abundant species collected, tended to be greater in canola monocultures than high-wheat intercrops or wheat monocultures. We conclude that intercrops of canola and wheat have the potential to enhance populations of some carabid species, therefore possibly exerting increased pressure on some canola insect pests.
  • Authors:
    • Quideau, S.
    • Pswarayi, A.
    • Nelson, A. G.
    • Frick, B.
    • Spaner, D.
  • Source: Agronomy Journal
  • Volume: 104
  • Issue: 3
  • Year: 2012
  • Summary: To investigate intercropping as a management strategy to increase crop productivity and weed suppression in organic systems, spring wheat ( Triticum aestivum L.), barley ( Hordeum vulgare L.), canola ( Brassica napus L.) and field pea ( Pisum sativum L.) monocultures were compared with two-, three-, and four-crop intercrops containing wheat at two organic and one conventional site in 2006 and 2007, central Alberta, Canada. We measured crop and weed biomass, grain yield, and crop competitiveness against weeds from a replacement design in a completely randomized block experiment. Pea and canola monocrops on organic sites yielded the least of all crop treatments. Conventional crop treatments generally yielded higher than organic treatments. Few land equivalent ratios (LERs) on organic sites were significantly >1.0. Some wheat intercrops without barley showed overyielding (LER >1.0) potential. Most of the significant LERs were from three- and four-crop intercrops. More than 50% of the intercrops on organic sites significantly suppressed weeds (based on relative weed biomass) and most of these intercrops had barley in the mixture. Barley as a sole crop and in intercrops suppressed weeds better than all other intercrops and sole crops. The wheat-canola intercrop exhibited the best weed suppression of the two-crop intercrops on organic and conventional sites. The crop densities used in this study may have contributed to the extremely low pea and canola monocrop yields as well as low LERs. Due to this, our findings should be regarded as showing trends and potential from intercrops only. We therefore recommend further studies to establish ideal densities for the intercrops used.