Conservation practices in U.S. agriculture and their impact on carbon sequestration

Increase in the use of conservation practices byagriculture in the United States will enhance soilorganic carbon and potentially increase carbonsequestration. This, in turn, will decrease the netemission of carbon dioxide. A number of studies existthat calibrate the contribution of various individual,site-specific conservation practices on changes insoil organic carbon. There is a general absence,however, of a comprehensive effort to measureobjectively the contribution of these practicesincluding conservation tillage, the ConservationReserve Program, and conservation buffer strips to anchange in soil organic carbon. This paper fills thatvoid. After recounting the evolution of the use ofthe various conservation practices, it is estimatedthat organic carbon in the soil in 1998 in the UnitedStates attributable to these practices was about 12.2million metric tons. By 2008, there will be anincrease of about 25%. Given that there is asignificant potential for conservation practices tolead to an increase in carbon sequestration, there area number of policy options that can be pursued.     

Soil heavy metal contamination in an industrial area: analysis of the data collected during a decade

Soil contamination by heavy metals has become a serious problem mainly because, above certain concentrations, all metals have adverse effects on human health. In particular, the accumulation of heavy metals in agricultural soils leads to elevated uptake by crops and affects food quality and safety. In this paper, we present the results of a study carried out over a decade for evaluating the impact of a new industrial settlement in an area geared to agriculture and livestock and far from urban sites. We focus our study on the bioavailable fraction of Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn in soil samples. Heavy metal concentrations in soil are analysed with both univariate and multivariate statistical procedures. The main goal of this paper is the development of a statistical procedure, based on a mix of multivariate analysis, able to compare field surveys carried out during different years and to characterize spatial and temporal changes in soil heavy metals concentrations.     

Agro-economic evaluation of water resource project--a modeling approach

Feasibility of an irrigation project is evaluated by two criteria viz., reservoir capacity to irrigate its command area and economic returns by incremental crop production versus capital investment for dam construction. The annual water requirement of different crops in the command area is estimated and compared with the availability of water from the dam for irrigation purpose. The annual crop water requirement is estimated as the sum of evapotranspiration for crops and transmission and other losses. Evapotranspiration is estimated by modified Penman formula. Economics of crop production is analyzed by first estimating the monetary value of existing crop production under current rain fed conditions and then estimating the incremental production of irrigated command area for the proposed crop pattern. The proposed cropping pattern is prepared so as to maximize the benefit of crop production and fodder requirement while maintaining a better crop rotation to improve and maintain physical, chemical, and biological conditions of the soil. The dam is to be used for irrigation and water supply only. Command area served by this reservoir will be 76,500 ha. The existing annual agricultural return is Rs. 2995.56 lakhs and with the proposed irrigation scheme, it is estimated as Rs. 1,77,91.90 lakhs. The incremental annual return would be Rs. 1,47,96.35 lakhs i.e., 642.68% increase in annual return.     

Soil and vegetation carbon stocks in Brazilian Western Amazonia: relationships and ecological implications for natural landscapes

The relationships between soils attributes, soil carbon stocks and vegetation carbon stocks are poorly know in Amazonia, even at regional scale. In this paper, we used the large and reliable soil database from Western Amazonia obtained from the RADAMBRASIL project and recent estimates of vegetation biomass to investigate some environmental relationships, quantifying C stocks of intact ecosystem in Western Amazonia. The results allowed separating the western Amazonia into 6 sectors, called pedo-zones: Roraima, Rio Negro Basin, Tertiary Plateaux of the Amazon, Javari-Juruá-Purus lowland, Acre Basin and Rondonia uplands. The highest C stock for the whole soil is observed in the Acre and in the Rio Negro sectors. In the former, this is due to the high nutrient status and high clay activity, whereas in the latter, it is attributed to a downward carbon movement attributed to widespread podzolization and arenization, forming spodic horizons. The youthful nature of shallow soils of the Javari-Juruá-Purus lowlands, associated with high Al, results in a high phytomass C/soil C ratio. A similar trend was observed for the shallow soils from the Roraima and Rondonia highlands. A consistent east–west decline in biomass carbon in the Rio Negro Basin sector is associated with increasing rainfall and higher sand amounts. It is related to lesser C protection and greater C loss of sandy soils, subjected to active chemical leaching and widespread podzolization. Also, these soils possess lower cation exchangeable capacity and lower water retention capacity. Zones where deeply weathered Latosols dominate have a overall pattern of high C sequestration, and greater than the shallower soils from the upper Amazon, west of Madeira and Negro rivers. This was attributed to deeper incorporation of carbon in these clayey and highly pedo-bioturbated soils. The results highlight the urgent need for refining soil data at an appropriate scale for C stocks calculations purposes in Amazonia. There is a risk of misinterpreting C stocks in Amazonia when such great pedological variability is not taken into account.     

Environmental assessment and investment strategies of provincial industrial sector in China — Analysis based on DEA model

As an energy-intensive industry, the industrial sector consumes 70% of energy consumption and causes serious environmental pollution in China. Also, the government emphasized the promotion of R&D investment in the industrial sector in China's National Plan on Climate Change (2014–2020). It is meaningful and contributes to assessing energy and environmental performance, as well as R&D and industrial pollution control (IPC) investment strategies of China's industrial sector. A non-radial DEA model, as with natural and managerial disposability, was adopted to evaluate this from provincial and regional perspectives during the 2008–2012 period. Energy and environmental performance was evaluated by unified efficiency under natural disposability (UEN), unified efficiency under managerial disposability (UEM), and unified efficiency under natural and managerial disposability (UENM). The empirical results indicated that Shandong and Hainan were efficient under natural and managerial disposability, while other provinces had the potential to improve their energy and environmental performance. The number of provinces that was fit for investments of R&D and IPC increased from 2008 to 2010, then decreased in 2011 and 2012. In spite of this, many provincial industrial sectors should make efforts to reduce pollution by investment on technology. Tianjin, Heilongjiang, Jiangxi and Henan were especially the best investment objects because investments of R&D and IPC turned to be effective for them during the whole study period. Moreover, western China had the highest average UENM, followed by eastern China and central China. Eastern China and central China were rewarding to expand investments. Coal consumption was the main factor to negatively affect unified efficiency whereas the increase in economic development level was primarily responsible for the improvement of unified efficiency. According to the results, differentiated suggestions to further improve energy and environmental performance were proposed.     

Impact of sewage contaminated water on soil, vegetables, and underground water of peri-urban Peshawar, Pakistan

The use of sewage-contaminated municipal water for irrigation of crops is an old practice in many big cities of Pakistan. Since the wastewater is rich in nutrients, it increases crops yield substantially but at the cost of food quality. The objective of this study was to investigate sewage water irrigation as a source of accumulation of heavy metals in soil and its subsequent transfer to crops and underground water. Sewage water, soil, groundwater, and crop samples were collected from selected areas around Peshawar city and analyzed for heavy metals concentration by atomic absorption spectroscopic method. Analysis of data revealed a considerable impact of the irrigation practices in the peri-urban Peshawar. Statistical analysis of the data showed a positive correlation between heavy metals concentration and soil carbon contents on the one hand and cation exchange capacity on the other. A strongly negative correlation was observed between metal contents and soil pH. The vertical movement of heavy metals from contaminated soil has polluted crops and underground water. The results indicated higher concentration of toxic metals in soil accumulated due to long-term sewage-contaminated water irrigation and their subsequent transfer to our food chain. The practice, if continued un-noticed may pose a threat of phytotoxicity to the local population.     

A method for assessing generalised nitrogen leaching estimates for agricultural land

The purpose of this study was to develop a method for assessing generalised N leaching estimates from large areas of agricultural land. The system developed was based on calculating a number of N leaching estimates for different typical cropping situations. The estimates were normalised with respect to varying weather conditions and crop production. The different cropping situations were described by setting up a matrix consisting of crucial factors influencing leaching such as soils, crops and climate. Nitrogen leaching was then estimated for a number of combinations of these factors. Calculations were made for three different regions where all the major crops were cultivated on soils with seven different textures and four different organic-N classes and two fertilisation regimes. The three regions are representative of climates and agricultural practices in some of the major agricultural areas in Sweden. The model used was the SOILN model. Leaching of nitrogen from the root zone showed large variations. The range was from 1 to 50 kg ha⁻¹ for different soils and crops when only fertiliser N was applied. Leaching varied both due to different climates and differences in cultivation practices between the regions. Leaching decreased in a south-north gradient. Leaching increased as a result of greater mineralisation when the organic matter content in the soils was increased, leaching was less from soils with a high clay content and was very small for the heavy clay soil. This revised version was published online in July 2006 with corrections to the Cover Date.     

Implementing the montreal protocol in china: Use of cleaner technology in two industrial sectors

An analysis of the household refrigeration sector and the foams sector investigates how Chinese enterprises have adopted cleaner technologies involving substitutes for ozone depleting substances (ODSs), such as chlorofluorocarbons (CFCs). The performance of the household refrigeration sector in reducing ODS consumption has been superior to that of the foams sector, even though required technology changes are relatively simple for the foams sector. There are two explanations for this outcome. First, market demand matters. The influence of the global market, multinational corporations, intense (and occasionally misleading) advertising about non-CFC products, and severe competition for consumers caused China's principal refrigerator manufacturers to adopt non-CFC production technologies. Similar incentives did not exist for enterprises in the foams sector. Second, industrial structure matters. The foams sector includes a large number of small enterprises with limited financial and technical capability and weak access to information and technology, and these factors obstructed technological change. In general, assistance from the Multilateral Fund established under the Montreal Protocol has motivated enterprises to shift to ODS reduction technologies, but complex and lengthy procedures for accessing the Multilateral Fund, difficulties in finding appropriate suppliers of non-CFC technologies, and insufficient financial and technical capabilities of many enterprises have slowed down this shift. Our results provide a foundation for making changes in international assistance programs and China's strategies for CFC reduction.     

Variations and trends of ground-level ozone and AOT40 in the rural areas of Lithuania

The analysis of data of the ground-level ozone concentration and accumulated ozone exposure over a threshold of 40 ppb (AOT40) in the rural areas of Lithuania is presented. Trends in the annual ozone mean, 95{th} and 25{th} percentiles were determined as statistically not significant at Preila and Rugsteliskes sites during the 1994hbox{–}2004 period. Trends in the ozone concentration and its percentiles in the air masses arriving to Preila station in “polluted” and “unpolluted” sectors have been examined. Statistically significant changes in the ozone annual mean and 25th percentile were found in air masses in both “polluted” and “unpolluted” sectors in the 1988hbox{–}2002 period. The trend analysis in the ozone monthly mean and percentiles for each month of the year revealed the main changes in the ozone level in both sectors during January-May. Insignificant downward trends in monthly 95th percentile in “unpolluted” sector and upward trends in “polluted” sector were found during summer months. Values of AOT40 for the protection of forests as well as crops and semi-natural vegetation were determined during the 1994–2004 period. The estimated AOT40 values for the protection of forests were lower than the critical level at Lithuanian rural sites but AOT40 values for the protection of crops and semi-natural vegetation were found to be higher than the critical level at both sites.     

Atmospheric heavy metals in tropical South America during the past 22,000 years recorded in a high altitude ice core from Sajama, Bolivia

V, Co, Cu, Zn, As, Rb, Sr, Ag, Cd, Ba, Pb, Bi and U have been analysed by inductively coupled plasma sector field mass spectrometry in various sections of a dated snow/ice core drilled at an altitude of 6542 m on the Sajama ice cap in Bolivia. The analysed sections were dated from the Last Glacial Stage ( approximately 22,000 years ago), the Mid-Holocene and the last centuries. The observed variations of crustal enrichment factors (EFc) for the various metals show contrasting situations. For V, Co, Rb, Sr and U, EFc values close to unity are observed for all sections, then showing that these elements are mainly derived from rock and soil dust. For the other metals, clear time trends are observed, with a pronounced increase of EFc values during the 19th and 20th centuries. This increase shows evidence of metal pollution associated with human activity in South America. For Pb an important contribution was from gasoline additives. For metals such as Cu, Zn, Ag and Cd an important contribution was from metal production activities, with a continuous increase of production during the 20th century in countries such as Peru, Chile and Bolivia.     

Copper and Zinc in a paddy field and their potential ecological impacts affected by wastewater from a lead/zinc mine, P. R. China

As well known, at normal levels, copper and zinc are essential micronutrients for plants, animals, and humans. However, excessive Cu and Zn are toxic and disturb a wide range of biochemical and physiological processes. Using Atomic Absorption Spectrophotometer (AAS; Perkin-Elmer 3030, USA), soil and rice plant (Oryza sativa L.) samples collected from a paddy field in Lechang lead-zinc mine area, Guangdong Province, China were analyzed and their potential ecological impacts to local human and livestock were evaluated. The results showed that the paddy soils were contaminated with Cu and Zn. Both metals in soils had low bio-available fractions for paddy plants, animal and human by three chemically analytical techniques. Generally, were concentrations of copper and zinc root > straw > stalk > grain with hull > grain without hull (i.e. unpolished rice) and in the normal ranges indicating no ecological risk for local livestock and residents. All positive correlation coefficients, however, between heavy metals in rice plant and total, exchangeable (step 1 in Tessier's method established in 1979) and DTPA-extractable fractions in soils were found in this study indicating that elevated heavy metal in soils would increase long-term exposition and possible consequence of ecological hazard through food chains.     

Regulating Water Quantity and Quality in Irrigated Agriculture: Learning by Investing under Asymmetric Information

An input-based incentive approach for controlling an agricultural non-point source pollution problem is developed. A regulatory agency designs a tax scheme and an investment policy to increase its informational base, in order to obtain the desirable water use and emissions for a set of agricultural producers whose individual water use and emissions cannot be observed without costly monitoring. The agency invests in order to increase observability of water use and emissions, and taxes the observed variables. Learning effects enhance the process of acquiring information about the individual producers' behavior. The optimal tax scheme and the cost minimizing monitoring program are determined. This revised version was published online in July 2006 with corrections to the Cover Date.     

Atmospheric inorganic nitrogen deposition to a typical red soil forestland in southeastern China

A 2-year monitoring study was conducted to estimate nitrogen deposition to a typical red soil forestland in southeastern China. The dry deposition velocities (V(d)) were estimated using big leaf resistance analogy model. Atmospheric nitrogen dry deposition was estimated by combing V(d) and nitrogen compounds concentrations, and the wet deposition was calculated via rainfall and nitrogen concentrations in rainwater. The total inorganic nitrogen deposition was 83.7 kg ha(-1) a(-1) in 2004 and 81.3 kg ha(-1) a(-1) in 2005, respectively. The dry deposition contributed 78.6% to total nitrogen deposition, in which ammonia was the predominant contributor that accounted for 86.1%. Reduced nitrogen compounds were the predominant contributors, accounting for 78.3% of total nitrogen deposition. The results suggested that atmospheric inorganic nitrogen could be attributed to intensive agricultural practices such as excessive nitrogen fertilization and livestock production. Therefore, impacts of atmospheric nitrogen originated from agriculture practices on nearby forest ecosystems should be evaluated.     

Modeling of Ecological Footprint and Climate Change Impacts on Food Security of the Hill Tracts of Chittagong in Bangladesh

This paper presents an integrated and dynamic model for the management of the uplands of the Hill Tracts of Chittagong to predict food security and environmental loading for gradual transition of shifting agriculture land into horticulture crops and teak plantation, and crop land into tobacco cultivation. Food security status for gradual transmission of shifting agriculture land into horticulture crops and teak plantation, and crop land into tobacco cultivation is the best option for food security, but this causes the highest environmental loading resulting from tobacco cultivation. Considering both food security and environmental degradation in terms of ecological footprint, the best option is gradual transition of shifting agriculture land into horticulture crops which provides moderate increase in the food security with a relatively lower environmental degradation in terms of ecological footprint. Crop growth model InfoCrop was used to predict the climate change impacts on rice and maize production in the uplands of the Hill Tracts of Chittagong. Climate change impacts on the yields of rice and maize of three treatments of temperature, carbon dioxide and rainfall change (+0 °C, +0 ppm and +0 % rainfall), (+2 °C, +50 ppm and 20 % rainfall) and (+2 °C, +100 ppm and 30 % rainfall) were assessed. The yield of rice decreases for treatment 2, but it increases for treatment 3. The yield of maize increases for treatments 2 and 3 since maize is a C₄ plant. There is almost no change in food security at upazila (sub-district) level for the historical climate change scenario, but there is small change in the food security at upazila levels for IPCC climate change scenario.     

Mitigation Portfolio and Policy Instruments When Hedging Against Climate Policy and Technology Uncertainty

In this paper, we use a stochastic integrated assessment model to evaluate the effects of uncertainty about future carbon taxes and the costs of low-carbon power technologies. We assess the implications of such ambiguity on the mitigation portfolio under a variety of assumptions and evaluate the role of emission performance standards and renewable portfolios in accompanying a market-based climate policy. Results suggest that climate policy and technology uncertainties are important with varying effects on all abatement options. The effect varies with the technology, the type of uncertainty, and the level of risk. We show that carbon price uncertainty does not substantially change the level of abatement, but it does have an influence on the mitigation portfolio, reducing in particular energy R&D investments in advanced technologies. When investment costs are uncertain, investments are discouraged, especially during the early stages, but the effect is mitigated for the technologies with technological learning prospects. Overall, these insights support some level of regulation to encourage investments in coal equipped with carbon capture and storage and clean energy R&D.     

Estimating the mitigation potential of the Chinese service sector using embodied carbon emissions accounting

It is universally recognized that direct carbon emissions based on energy consumption and industrial production lead to carbon leakage and inequality. This paper employs input–output analysis (IOA) and the hypothetical extraction method (HEM) to establish an embodied carbon analysis framework to resolve the above externalities. As a typical downstream consumption industry, the service sector has had very little work examining its embodied carbon transfer structure and related climate policies. In this paper, carbon flows of China's service sector between 1997 and 2015 are mapped and a scenario analysis is conducted that accounts for the service sector development plan and carbon emissions reduction targets. The results demonstrate that 13–19% of carbon flows in the Chinese economy are caused by the service sector's demand of other sectors. Controlling the industry scale and carbon intensity of its upstream industries effectively mitigates the dramatic growth of embodied carbon emissions in the service sector. The embodied carbon emissions accounting framework might provide new insights for the definition of emissions reduction responsibility on both a regional and sectoral scale. The further exploration of the service industry from this novel perspective will be helpful in realizing China's overall carbon emissions reduction goals.     

An analytical model for the assessment of pesticide exposure levels in soils and groundwater

The movement and degradation of pesticide residues in soils and groundwater are complex processes affected by soil physical, (bio)chemical, and hydrogeological properties, climatic conditions, and agricultural practices. This work presents a physically-based analytical model suitable for long-term predictions of pesticide concentrations in groundwater. The primary interest is to investigate the impact of soil environment, related physical and (bio)chemical processes, especially, volatilization, crop uptake, and agricultural practices on long-term vulnerability of groundwater to contamination by pesticides. The soil is separated into root and intermediate vadose zones, each with uniform properties. Transport in each soil zone is modeled on the basis of complete mixing, by spatial averaging the related point multiphase-transport partial differential equation (i.e., linear-reservoir models). Transport in the aquifer, however, is modeled by a two-dimensional advection-dispersion transport equation, considering adsorption and first-order decay rate. Vaporization in the soil is accounted for by assuming liquid-vapor phase partitioning using Henry's law, and vapor flux (volatilization) from the soil surface is modeled by diffusion through an air boundary layer. Sorption of liquid-phase solutes by crops is described by a linear relationship which is valid for first-order (passive) crop uptake. The model is applied to five pesticides (atrazine, bromacil, chlordane, heptachlor, and lindane), and the potential for pesticide contamination of groundwater is investigated for sandy and clayey soils. Simulation results show that groundwater contamination can be substantially reduced for clayey soil environments, where bio(chemical) degradation and volatilization are most efficient as natural loss pathways for the pesticides. Also, uptake by cross can be a significant mechanism for attenuating exposure levels in ground-water especially in a sandy soil environment, and for relatively persisting pesticides. Further, simulations indicate that changing agricultural practices can have a profound effect on vulnerability of groundwater to mobile and relatively persisting pesticides.     

Accumulation of heavy metals in dietary vegetables and cultivated soil horizon in organic farming system in relation to atmospheric deposition in a seasonally dry tropical region of India

Increasing consciousness about future sustainable agriculture and hazard free food production has lead organic farming to be a globally emerging alternative farm practice. We investigated the accumulation of air-borne heavy metals in edible parts of vegetables and in cultivated soil horizon in organic farming system in a low rain fall tropical region of India. The factorial design of whole experiment consisted of six vegetable crops (tomato, egg plant, spinach, amaranthus, carrot and radish) x two treatments (organic farming in open field and organic farming in glasshouse (OFG)) x seven independent harvest of each crop. The results indicated that except for Pb, atmospheric deposition of heavy metals increased consistently on time scale. Concentrations of heavy metals in cultivated soil horizon and in edible parts of open field grown vegetables increased over time and were significantly higher than those recorded in OFG plots. Increased contents of heavy metals in open field altered soil porosity, bulk density, water holding capacity, microbial biomass carbon, substrate-induced respiration, alkaline phosphatase and fluorescein diacetate hydrolytic activities. Vegetable concentrations of heavy metal appeared in the order Zn > Pb > Cu > Ni > Cd and were maximum in leaves (spinach and amaranths) followed by fruits (tomato and egg plant) and minimum in roots (carrot and radish). Multiple regression analysis indicated that the major contribution of most heavy metals to vegetable leaves was from atmosphere. For roots however, soil appeared to be equally important. The study suggests that if the present trend of atmospheric deposition is continued, it will lead to a destabilizing effect on this sustainable agricultural practice and will increase the dietary intake of toxic metals.     

上海地区土壤碳汇功能评估

利用上海市第二次土壤普查资料,2004年-2005年上海耕地地力调查资料,以及2009年实地调查采样、实验分析获得的数据,研究了3个时期上海土壤有机碳的变化特征。结果表明,20多年：来上海土壤有机碳平均含量没有明显变化,土壤有机碳库逐渐减小,从而使得上海城市化过程中土壤成为一种碳源,而不是碳汇。城市郊区以扩大蔬菜、果树、苗木种植为特征的旱地作物种植方式代替水稻田,是城市化影响土地利用类型变化的明显特征,而水稻田土壤有机碳含量高于林地、菜地。种植结构的变化对土壤有机碳含量有重要影响,同时,耕作制度、耕作方式、施肥等农业管理方式也有一定影响。虽然园林绿地得到快速发展,但没有弥补城市化过程导致农田面积减少带来的有机碳损失。