加强秸秆禁烧和综合利用促进农业和农村节能减排

节能减排,是党中央、国务院作出的重大战略部署,是转变经济发展方式、实现经济社会又好又快发展的必南之路。积极推广秸秆综合利用技术,防止违规焚烧秸秆,对于促进农业和农村节能减排目标的实现,具有十分重要的意义。     

A comparative study of the energy budget of hill agro-ecosystems with emphasis on the slash and burn system (JHUM) at lower elevations of North-Eastern India

The present study is a comparison of the energy efficiency of three types of shifting agriculture, known locally as ‘jhum’, in north-eastern India. Longer cycles of 30 and 10 years, which are rather rare now, are compared with the more common 5-year cycle of the present time. Of the three land use practices, jhum and valley agricultural systems are more efficient from the energy viewpoint, with higher output/input ratios compared with terrace cultivation, which is least efficient due to heavy fertiliser input requirements. For jhum, a 10-year cycle, however, is more efficient from the energy and land use points of view, with an effective energy output of 5660·1 MJ compared with 1892·2 MJ under a 30-year cycle or 4771·6 MJ under a 5-year cycle. Cereal cultivation, if its is to be sustained, must be on the basis of valley cultivation, which is sustainable year after year, or on basis of a 10-year jhum cycle. The implications of these findings are discussed in the light of the relative significance of land and energy constraints.     

Managing water in agriculture for food production and other ecosystem services

Agricultural systems as well as other ecosystems generate ecosystem services, i.e., societal benefits from ecological processes. These services include, for example, nutrient reduction that leads to water quality improvements in some wetlands and climatic regulation through recycling of precipitation in rain forests. While agriculture has increased ‘provisioning’ ecosystem services, such as food, fiber and timber production, it has, through time, substantially impacted other ecosystem services. Here we review the trade-offs among ecosystem services that have been generated by agriculture-induced changes to water quality and quantity in downstream aquatic systems, wetlands and terrestrial systems. We highlight emerging issues that need urgent attention in research and policy making. We identify three main strategies by which agricultural water management can deal with these large trade-offs: (a) improving water management practices on agricultural lands, (b) better linkage with management of downstream aquatic ecosystems, and (c) paying more attention to how water can be managed to create multifunctional agro-ecosystems. This can only be done if ecological landscape processes are better understood, and the values of ecosystem services other than food production are also recognized.     

Impact of upstream changes in rain-fed agriculture on downstream flow in a semi-arid basin

The downstream impacts of increasing water consumption in the upstream rain-fed areas of the Karkheh Basin, Iran are simulated using the semi-distributed SWAT model. Three scenarios are tested at subbasin and basin levels: converting rain-fed areas to irrigation agriculture (S1), improving soil water availability through rainwater harvesting (S2), and a combination of both (S3). The results of these scenarios were compared against the baseline period 1988-2000. The S1 scenario shows a 10% reduction in mean annual flow at the basin level, varying from 8-15% across the subbasins. The reductions in mean monthly flows are in the range of 1-56% at the basin level, with June witnessing the highest flow reduction. Flow reductions are comparatively higher in the upstream parts of the basin, as a result of a relatively higher potential of developing rain-fed areas coupled with comparatively lower amount of available runoff. The impacts of S2 are generally small with reductions of 2-5% and 1-9% in mean annual and mean monthly flows, respectively. The results of S3 are in general similar to those of S1. Although the estimated annual flow reductions remain well within the available water resources development potential, measures needs to be taken to avoid excessive flow reductions in May, June and July. It is recommended that only a limited agricultural area should be converted from rain-fed to irrigated agriculture (about 0.1 million ha), and should practice supplementary irrigation. The supplies should also be augmented through developing additional water storage. Adopting such measures is extremely important for the upper subbasins Gamasiab and Qarasou where comparatively higher flow reductions were estimated.     

Cropping systems and crop residue management in the Trans-Gangetic Plains: Issues and challenges for conservation agriculture from village surveys

Conservation agriculture practices are being advocated to help sustain crop productivity gains and secure environmental sustainability in the Trans-Gangetic Plains, India’s Green Revolution heartland. The paper illustrates the use of village surveys as a quasi-quantitative system analysis tool to derive implications for agricultural research and development. Drawing from village surveys in 170 communities, the paper assesses current crop residue management practices in Punjab and Haryana’s rice-wheat, basmati-wheat and non-rice-wheat cropping systems. The prevalence of wheat as the winter crop implies an intensive collection, trading and use of wheat straw as basal feed for dairy livestock; which contrasts with the diverse crop residue management of the monsoon crops. The increased use of combine harvesters has spurred the rapid advent of mechanical wheat straw reapers whereas the bulk of combine harvested rice straw is burned in situ. Present crop residue management practices are largely incompatible with year-round mulch retention despite significant biomass production. The research and development community faces the challenge of evening out straw use and management over seasons to ensure at least partial residue retention if its calls for conservation agriculture in this important sub-region are to succeed. The paper also reiterates the worrying decline of groundwater tables associated with the rice-wheat system.     

Bio-resource flow in integrated agriculture–aquaculture systems in a tropical monsoonal climate: a case study in Northeast Thailand

The degree of integration and intensification in integrated agriculture–aquaculture systems (IAAS) varies with the variation in the pattern of bio-resource flow among various enterprises. Bio-resource flow in IAAS in Northeast Thailand was studied across four different agroecologies, one irrigated and three rainfed (drought-prone, rainfed lowland and rolling land). Only the irrigated and one rainfed (drought-prone) agroecology had easy market accessibility. Patterns of bio-resource flow clearly varied between IAAS as most enterprises in the irrigated agroecology functioned independently with a low degree of integration based on bio-resource flow among the enterprises compared with a high degree of integration among enterprises in the rainfed agroecologies. However, market accessibility played a crucial role in intensification of IAAS regardless of agroecology. Households with integrated systems in irrigated and drought-prone agroecologies applied adequate chemical fertilisers to fruit and vegetables to realize high gross incomes from these enterprises. In contrast, households in rainfed lowland and rolling land agroecologies operated subsistence IAAS as they relied more on organic manure from on- or off-farm sources with corresponding low gross income. Fish culture in farm ponds was a low-input system in all agroecologies but resource-use efficiency based on assessment of total N in pond inputs and N removed in fish harvest appeared to be relatively high. A combination of resource base and market accessibility can be envisaged to play the key role in the development of viable IAAS in Northeast Thailand.     

River flow prediction through rainfall–runoff modelling with a probability-distributed model (PDM) in Flanders, Belgium

The hydrological probability-distributed model (PDM) is widely used all over the world and its applicability has also been investigated in Flanders, Belgium. Rainfall–discharge relations for all gauging stations installed on non-navigable watercourses were modelled over a long succession of monitoring years. In all, 1456 years were modelled. Typical characteristics (peak flow, volumes) of modelled series are compared with observations. Based on the relatively long time series, reliable discharge values can be generated with the PDM. Water volumes and peak characteristics are very close to the observed values. The set of 98 PDMs was analysed and clustered. Three cluster approaches were considered: a single-parameter approach, a parameter set approach and an approach with known cluster zones, delineated on hydrological flow characteristics. The single-parameter approach, the parameter set approach and the combination of both gave less detailed regional information than the clustering on hydrological characteristics.     

我国精确农业发展现状及前景展望

精确农业是基于信息和知识支持的集成技术管理的现代化农业。它是高效利用农业资源、减少环境污染、保持农业可持续发展的系统工程。简要介绍了支持精确农业系统的主要技术、发展现状及其前景展望。     

农业机械化及农业产业化在建设社会主义新农村中的作用

建设社会主义新农村是党中央统筹城乡发展的重大战略决策,是我国现代化进程中的重大历史任务。建设社会主义新农村,必须以农村经济建设为中心,建设现代农业。农业机械化是构成农业综合生产能力的重要组成部分,是现代农业的重要物质基础,是农业现代化的重要内容和标志。加快发展农业机械化,是建设社会主义新农村的内在要求与必由之路,必须把它摆在重要的位置。全面建设社会主义新农村,也为农业机械化提出了更新、更高、更快的发展要求。本文着重就农业机械化及农业产业化在建设社会主义新农村中的作用进行探讨。     

Evaluation of simulation models in agriculture and biology: Conclusions of a workshop

A workshop on evaluation of simulation models was held in Wageningen. The object of the meeting was to discuss problems and points of view concerning evaluation of complex models. Most of the workshop was devoted to discussions. At the end, there was a considerable consensus on many points. This paper summarises the major conclusions.     

Food production and consumption in a Fijian village and an Indian settlement in the Sigatoka Valley,Fiji

This paper shows how a detailed analysis of production and consumption behaviour of subsistence and semi-subsistence farmers can be used for farm planning and development of rural communities. The study is based on a survey of a sample of Fijian and Indian semi-subsistence farmers in the Sigatoka Valley, Fiji. The results showed marked differences in the dietary patterns of the two communities and in the sources of food energy and protein amongst the various food commodities. The Indians were more efficient than the Fijians in meeting the food needs from their farms. The Fijians tended to purchase more store foods and also purchased more expensive sources of food energy and protein to supplement their diet. Finally, the results of this study are used to indicate pathways for national food policies for Fiji and other developing nations.     

Simulating soil water flow and nitrogen dynamics in a sunflower field irrigated with reclaimed wastewater

Soil water flow and nitrogen dynamics were simulated in sunflower field during and after the growing period, in Northern Greece. Soil water and nitrogen dynamics were evaluated using a one-dimensional simulation model based on the Galerkin finite element method. We examined the effects of irrigation with reclaimed wastewater and nitrogen fertilizer applications on plant growth, water and nitrogen distribution in the soil profile, water and nitrogen balance components and nitrogen leaching to groundwater. The model simulated the temporal variation of soil water content with reasonable accuracy. However, an over estimation of the measured data was observed during the simulation period. Relatively good agreement was found between the simulated and measured NH₄-N and NO₃-N concentrations over time and depth, whereas fluctuations at greater depths were relatively small. Most of the cumulative nitrate-N leaching (44.7 kg N ha⁻¹) occurred during the winter.     

能源生态环保型猪场粪污处理模式的应用

本文主要介绍了畜禽养殖场排泄物治理中的能源生态环保处理模式在浙江某种猪场的应用,详细介绍了该养殖场沼气工程的工艺路线、处理能力、工程规模以及工程调试运行情况.     

Probabilities for decision analysis in agriculture and rural resource economics: The need for a paradigm change

The notion that we can rationalize risky choice in terms of expected utility appears to be widely if not universally accepted in the agricultural and resource economics profession. While there have been many attempts to assess the risk preferences of farmers, there are few studies of their beliefs about uncertain events encoded as probabilities. We may attribute this neglect to scepticism in the profession about the concept of subjective probability. The general unwillingness to embrace this theory and its associated methods has all too often caused researchers to focus on problems for which frequency data are available, rather than on problems that are more important where data are generally sparse or lacking. In response, we provide a brief reminder of the merits of the subjectivist approach and extract some priorities for future research should there be a change of heart among at least some of the profession.     

喷灌分区的能量分析

文章分析了喷灌系统的能量组成及利用情况，在此基础上，提出了分区能量图解法，并得出一级建站与多级建站分区节省供水能量相同的结论．     

CFD and digital particle tracking to assess flow characteristics in the labyrinth flow path of a drip irrigation emitter

It is necessary to have a comprehensive understanding of the flow mechanisms within drip irrigation emitters to design emitters that have a high anti-clogging performance. The use of computational fluid dynamics (CFD) to research the flow characteristics is appropriate because the labyrinth flow path is narrow and its boundary is complex. In this paper, a CFD for numeric model was developed for numerical simulation of the velocity distribution and turbulence intensity distributions within labyrinth emitters. A two-dimensional digital particle-tracking velocimetry (2D-DPIV) visual display system of the full flow fields was also constructed using plain laser inducement fluorescence velocity measurement technology, custom-made fluorescent particles and a plane model of the emitters. The object lens of a microscope was fitted to a conventional charge coupled device (CCD) camera to overcome the contradiction problems between the image viewing area and resolution power within the flow path. The measured turbulence and velocity distribution characteristics within the labyrinth flow path were in good agreement with the calculated CFD results. This enabled the optimal emitter design patterns to be determined based on the hydraulic characteristics and clogging resistance in the labyrinth flow path.     

Urban growth, wastewater production and use in irrigated agriculture: a comparative study of Accra, Addis Ababa and Hyderabad

The relationships between urban development, water resources management and wastewater use for irrigation have been studied in the cities of Accra in Ghana, Addis Ababa in Ethiopia and Hyderabad in India. Large volumes of water are extracted from water sources often increasingly far away from the city, while investments in wastewater management are often lagging behind. The resulting environmental degradation within and downstream of cities has multiple consequences for public health, in particular through the use of untreated wastewater in irrigated agriculture. Despite significant efforts to increase wastewater treatment, options for safeguarding public health via conventional wastewater treatment alone remain limited to smaller inner-urban watersheds. The new WHO guidelines for wastewater irrigation recognize this situation and emphasize the potential of post- or non-treatment options. Controlling potential health risks will allow urban water managers in all three cities to build on the benefits from the already existing (but largely informal) wastewater reuse, those being the contribution to food security and reduction of fresh water demands.     

A model for recycling of feed nutrients in a crop,animal and biogas system in India

In northern India, with triple cropping intensity of fodder crops and recycling of feed nutrients in a milch animals and biogas system, from 1 ha of land it is possible to produce 82·63 GJ of energy and 906·11 kg of protein from milk; 263·93 kg of N; 148·93 kg of P₂O₅ and 90·94 kg of K₂O fertilizer from biogas slurry and 2897 kilowatts of power per annum for farm operation from biogas using the Kirloskar biogas engine. Traditional systems of wheat and rice cultivation can produce 93·87 GJ of energy and 654·25 kg of protein from food grain per hectare per annum. The recycling of feed nutrients in the available straws of rice and wheat crop can yield an additional 16·31 GJ of energy and 166·97 kg of protein from milk; 81·23 kg of N; 56·00 kg of P₂O₅ and 25·14 kg of K₂O fertilizer from biogas slurry and 1097 kilowatts of power per hectare annually from biogas.     

椭圆截面形状大回转消防水炮炮管内流数值模拟

以大回转型大流量消防水炮炮管为研究对象,对3种流量工况下圆截面和不同离心率椭圆截面消防水炮炮管内三维定常流动进行数值计算,分析不同截面炮管内流体水力损失和出口流态,得到截面变化对消防水炮炮管内部流动的影响规律,结果表明:在3种流量工况下,圆截面炮管与非圆截面炮管水力损失Δp差异较小,变化范围在2.7%以内;出口湍动能随着炮管截面的椭圆离心率增大而增大,从云图分布中可看出峰值且逐渐偏离管道的中心轴线;出口涡通量J随着椭圆离心率的增大而减小,可达到小于圆截面J值的情况,说明压扁管道可减小出口截面上旋涡强度;竖向椭圆截面炮管平均出口速度偏差■小于圆截面炮管出口值,且随椭圆离心率的增大而减小,表明竖向压扁管道带来更好的速度均匀分布．相同离心率的竖向椭圆截面炮管比横向的椭圆截面炮管的平均出口速度偏差值低21%,竖向压扁的方式优于横向压扁方式．大回转水炮炮管数值模拟对比后的结果表明,改变流道截面将改善出口流态．     

Modeling a weak turbulent flow in a narrow and wavy channel: case of micro-irrigation

The baffle-fitted labyrinth channel is commonly used in micro-irrigation systems. The flow in this labyrinth channel has a rather low-Reynolds number. In addition, emitter clogging, which is the major drawback of the micro-irrigation technique, is significantly related to flow characteristics. In order to design an anti-clogging emitter with a good performance, the hydrodynamics must be understood and analyzed. As CFD modeling is nowadays the most efficient approach for improving emitter geometry, this paper presents assessment of several k–\(\varepsilon\) turbulence models for computation of micro-irrigation emitter hydrodynamics. The objective is to determine the simplest and most efficient model to improve emitter conception, in terms of both discharge/pressure loss and limitation of the areas where low velocity is likely to generate emitter clogging. Low-Reynolds number k–\(\varepsilon\) models are often assumed to be more suitable for the labyrinth-channel flow since these models have no wall functions, they can take into account low turbulence levels and they account for the effect of damped turbulence. The low-Reynolds number k–\(\varepsilon\) models used in the present study are compared to high-Reynolds number k–\(\varepsilon\) models. Very different trends are observed between low-Reynolds number k–\(\varepsilon\) models. Some models reproduce a turbulent behavior, while others reproduce a laminar behavior. The head loss analysis reveals that, contrary to classical smooth pipe flow, the contribution of turbulent dissipation cannot be neglected since its contribution is larger than wall friction ones. This feature explains why different models can induce quite different flow behavior.