70年来陕西省纸坊沟流域农业生态经济系统耦合态势

"农业生态经济系统耦合"的研究与实践对于实现农业产业与资源相一致,建立持续、高效的农业生态经济系统具有重要的意义.耦合度可以阐明农业经济系统与农业生态系统互动关系,判定农业生态经济系统耦合态势.在分析陕西省纸坊沟流域农业生态经济系统耦合关系的基础上,参照系统科学等理论及相关研究结果建立了农业经济系统与农业生态系统耦合度模型,并计算和分析了该流域70a来的耦合度.结果表明,农业生态经济系统的耦合过程可以划分为4个阶段:Ⅰ.经济系统依赖生态资源进行原始化农业生产阶段;Ⅱ.农业生产掠夺式利用生态资源,生态系统供给能力不断减少阶段;Ⅲ. 农业经济系统与生态系统协调化发展阶段;Ⅳ.降低农业发展速度,促使生态系统重建阶段.纸坊沟流域从1938～2008年先后经历了第Ⅰ阶段、第Ⅱ阶段和第Ⅲ阶段.目前处于第Ⅲ阶段,但在"系统发展"过程中已潜伏了越来越大的危机,到2018年系统耦合突破"协调"界限,"相悖态势"将明显表现出来.为此,纸坊沟流域必须调整产业布局,发展草畜产业,进行产业升级,优化产业结构,实现农业生态经济系统协调、持续发展.     

Agriculturally induced vegetation change, 1950–1975

Changes in worldwide grain production area are analyzed to assess the impact of major agricultural activity onglobal biomass. During the 26-year study period, nearly 1% of the earth's ice-free land surface was converted to grain production. This increase in agricultural area reduced the planetary biomass; however, it had minimal effect on net primary productivity. Geographically, the overall change caused by increased grain production has been to redistribute the planetary biomass poleward.     

Fertility and child mortality in rural Ethiopia: Gondar and Hararge regions

This paper presents fertility and child mortality estimates for agricultural households of the Gondar and Hararge regions, based on the 1981 Rural Demographic Survey. The study shows that fertility and child mortality are quite high in both regions as in the rest of the country. However, Hararge has significantly higher mean parity and child mortality than Gondar.     

Net carbon flux from agriculture: Carbon emissions, carbon sequestration, crop yield, and land-use change

There is a potential to sequester carbon in soil by changing agricultural management practices. These changes in agricultural management can also result in changes in fossil-fuel use, agricultural inputs, and the carbon emissions associated with fossil fuels and other inputs. Management practices that alter crop yields and land productivity can affect the amount of land used for crop production with further significant implications for both emissions and sequestration potential. Data from a 20-year agricultural experiment were used to analyze carbon sequestration, carbon emissions, crop yield, and land-use change and to estimate the impact that carbon sequestration strategies might have on the net flux of carbon to the atmosphere. Results indicate that if changes in management result in decreased crop yields, the net carbon flux can be greater under the new system, assuming that crop demand remains the same and additional lands are brought into production. Conversely, if increasing crop yields lead to land abandonment, the overall carbon savings from changes in management will be greater than when soil carbon sequestration alone is considered.     

Seasonally, Labor Scheduling, and Agricultural Intensification in the Nigerian Savanna

Human labor is the primary factor of production in indigenous agricultural systems, yet the organization and scheduling of labor, and effect of agricultural intensification on these processes, remain poorly understood. While most theoretical and empirical studies have emphasized overall labor input and efficiency, this study of the Kofyar of Nigeria analyzes the scheduling and mobilization of labor in ecological context. Detailed labor diaries for a sample of households over an entire agricultural cycle reveal intricate schedules that balance the labor demands of a variable crop complex with a set of complementary mechanisms for mobilizing labor. With rising population density and market impetus, the Kofyar have increased gross labor inputs, adjusted crop mixes to reduce weekly fluctuations in labor, and extended the agricultural season. Labor demands are met by three social mechanisms of labor mobilization, which offer varying sizes of labor pool, degree of flexibility, and type of compensation.     

Energy,Nitrogen, and Farm Surplus Transitions in Agriculture from Historical Data Modeling. France, 1882–2013.

This article addresses agricultural metabolism and transitions for energy, nitrogen, farm production, self‐sufficiency, and surplus from historical data since the nineteenth century. It builds on an empirical data set on agricultural production and production means in France covering 130 consecutive years (1882–2013). Agricultural transitions have increased the net production and surplus of farms by a factor of 4 and have zeroed self‐sufficiency. The energy consumption remained quasi‐stable since 1882, but the energy and nitrogen structure of agriculture fully changed. With an EROI (energy return to energy invested) of 2 until 1950, preindustrial agriculture consumed as much energy to function as it provided in exportable surplus to sustain the nonagricultural population. The EROI doubled to 4 over the last 60 years, driven, on the one hand, by efficiency improvements in traction through the replacement of draft animals by motors and, on the other hand, by the joint increase in crop yields and efficiency in nitrogen use. Agricultural energy and nitrogen transitions shifted France from a self‐sufficiency agri‐food‐energy regime to a fossil‐dependent food export regime. Knowledge of resource conversion mechanisms over the long duration highlights the effects of changing agricultural metabolism on the system's feeding capacity. Farm self‐sufficiency is an asset against fossil fuel constraints, price volatility, and greenhouse gas emissions, but it equates to lower farm surplus in support of urbanization.     

Switchgrass in California: where,and at what price?

This article assesses the potential of California agriculture to supply biofuel feedstock in the form of switchgrass. We construct a fully calibrated, multiregion, multi‐input and multioutput model of agricultural supply for California's Central Valley based on the principles of positive mathematical programming. We exploit agronomic information obtained from a biophysical model to estimate regional production functions for switchgrass. The model predicts the extent and location of potential feedstock production in the Central Valley. Our results suggest that switchgrass adoption rates differ widely among agricultural regions, and that switchgrass is not likely to displace specialty crops by much statewide.     

Child growth and the economic value of children in rural Bolivia

Previous investigations have yielded contradictory conclusions concerning the importance of the economic contribution of children to households in agricultural societies. The present study evaluates the significance of children 's economic input in rural Ancoraimes, Bolivia by using child growth as an indirect indicator of the economic value of children. Children whose households differed in size and age composition were compared on the basis of five anthropometric measurements. Children from households with many young, nonproducing children were found to be significantly smaller for their age than children from households with few nonproducing children. Absolute household size had no major effect on child growth. While young children have a negative effect on the growth of children in the household, the positive effect of children as they grow older appears to make up for this loss. In terms of child growth, children are neither a net liability nor a net asset to agricultural households in Ancoraimes.     

Pearl millet, a source of alpha amylase production by Bacillus licheniformis

The present study is concerned with the selection of economically available agricultural starchy substrate for the production of alpha amylase by Bacillus licheniformis. Different agricultural starchy substrates such as soluble starch, hordium, pearl millet, rice, corn, gram and wheat starch were tested for the production of alpha amylase by parental and its mutant derivatives. The production of alpha amylase was 10-folds better by the mutant strain B. licheniformis GCUCM-30 than the parental strain when pearl millet starch at 1.5% level and nutrient broth concentrations at the level of 0.25% was supplemented to the fermentation medium.     

广东土壤科学的发展历程与展望

土壤是农业生产的基础,是人类赖以生存的基石,也是人类食物与生态环境安全的保障。土壤学是解决人口-资源-环境-粮食矛盾的重要学科之一。广东土壤科学发展历史悠久,在食物安全、环境保护、减少贫困、退化土地恢复重建和生态系统稳定性维持等事关全省发展方面取得了许多重要的成绩,但目前我省面临着人均耕地面积少、后备土壤资源匮乏、土壤肥力下降、土壤环境日趋恶化以及水土流失依然严重等问题,因此我省土壤科学研究也将从生产农学和基础土壤发生学拓展到包括高效持续农业生产、土壤变化与全球气候变化相互关系、土壤可持续利用、数字化与信息化土壤、土壤污染监测及其修复等多功能的研究领域。     

Determination of Carbamates and Thiocarbamates in Water,Soil and Sediment of the Formoso River,TO, Brazil

Considering the increase in agricultural production in Brazil, the use of pesticides for this production, and that there are no studies on pesticides in the region, the presence of carbamates and thiocarbamates was investigated in different environmental compartments of the Formoso River, TO, Brazil, by UHPLC/MS/MS. The collections were made on the banks of this river, in the area of influence of the agricultural project. The active principles were not found in the soil and sediment samples, only the propoxur principle was found in the water, reaching values of up to 0.025 μg L^?1. It was found that the biodiversity of the Tocantinense savannah is under threat, because even though only one of the substances surveyed, propoxur and its derivatives, has been detected, they are substances of high toxicity and tendency to contaminate surface and groundwater to varying degrees and irreversible damage to different species.     

Modeling Agricultural Production Strategies in the Northern Rio Grande Valley, New Mexico

Diversification in agricultural techniques is a common strategy of risk minimization in nonindustrial societies. However, attribution of suboptimal behavior to risk minimization without consideration of the structure of risk and its environmental context obscures the complexity of agricultural decision-making. The productive potential of a prehistoric agricultural system that includes floodwater and dry farming and stream irrigation is modeled using Geographic Information System (GIS) analysis to evaluate whether diversification occurred as a response to population pressure or as a risk buffering strategy. The estimated productive potential of floodwater and irrigation farming is sufficient to have supported the estimated local population, suggesting that risk buffering is a more likely explanation. Floodwater farming and stream irrigation form a dual strategy that is effective at reducing risk. However, the potential of dry farming for subsistence production is insufficient for buffering more than a 2% productive shortfall. We propose that, within this generally risk-averse economy, dry farming was oriented toward the production of nonsubsistence crops such as cotton.     

福建长泰热带、亚热带果树避冻气候区划

本文以热带、亚热带果树安全越冬的气候因子为主导指标,应用计算机地理信息系统ArcView,就长泰县果树避冻进行气候区划,为指导农业生产和农业规划提供科学依据。     

Agricultural sustainability: concepts, principles and evidence

Concerns about sustainability in agricultural systems centre on the need to develop technologies and practices that do not have adverse effects on environmental goods and services, are accessible to and effective for farmers, and lead to improvements in food productivity. Despite great progress in agricultural productivity in the past half-century, with crop and livestock productivity strongly driven by increased use of fertilizers, irrigation water, agricultural machinery, pesticides and land, it would be over-optimistic to assume that these relationships will remain linear in the future. New approaches are needed that will integrate biological and ecological processes into food production, minimize the use of those non-renewable inputs that cause harm to the environment or to the health of farmers and consumers, make productive use of the knowledge and skills of farmers, so substituting human capital for costly external inputs, and make productive use of people's collective capacities to work together to solve common agricultural and natural resource problems, such as for pest, watershed, irrigation, forest and credit management. These principles help to build important capital assets for agricultural systems: natural; social; human; physical; and financial capital. Improving natural capital is a central aim, and dividends can come from making the best use of the genotypes of crops and animals and the ecological conditions under which they are grown or raised. Agricultural sustainability suggests a focus on both genotype improvements through the full range of modern biological approaches and improved understanding of the benefits of ecological and agronomic management, manipulation and redesign. The ecological management of agroecosystems that addresses energy flows, nutrient cycling, population-regulating mechanisms and system resilience can lead to the redesign of agriculture at a landscape scale. Sustainable agriculture outcomes can be positive for food productivity, reduced pesticide use and carbon balances. Significant challenges, however, remain to develop national and international policies to support the wider emergence of more sustainable forms of agricultural production across both industrialized and developing countries.     

Land use efficiency: anticipating future demand for land‐sector greenhouse gas emissions abatement and managing trade‐offs with agriculture,water, and biodiversity

Competition for land is increasing, and policy needs to ensure the efficient supply of multiple ecosystem services from land systems. We modelled the spatially explicit potential future supply of ecosystem services in Australia's intensive agricultural land in response to carbon markets under four global outlooks from 2013 to 2050. We assessed the productive efficiency of greenhouse gas emissions abatement, agricultural production, water resources, and biodiversity services and compared these to production possibility frontiers (PPFs). While interacting commodity markets and carbon markets produced efficient outcomes for agricultural production and emissions abatement, more efficient outcomes were possible for water resources and biodiversity services due to weak price signals. However, when only two objectives were considered as per typical efficiency assessments, efficiency improvements involved significant unintended trade‐offs for the other objectives and incurred substantial opportunity costs. Considering multiple objectives simultaneously enabled the identification of land use arrangements that were efficient over multiple ecosystem services. Efficient land use arrangements could be selected that meet society's preferences for ecosystem service provision from land by adjusting the metric used to combine multiple services. To effectively manage competition for land via land use efficiency, market incentives are needed that effectively price multiple ecosystem services.     

Women's labor,fertility, and the introduction of modern technology in a rural Maya village

The introduction of mechanized technology into a rural Maya agricultural community in the mid 1970s markedly increased the technology with which maize could be ground and water collected, which in turn introduced a possible savings in the time spent working. This study investigated the response of female fertility to the introduction of this labor-saving technology. Using two proximate determinants of female fertility, the association between the advent of modern technology and changes in the age at which women give birth to their first child and the length of mothers' birth intervals was examined. Analyses showed that women begin their reproductive careers at a younger age after the laborsaving technology was introduced. Estimate of the median age at first birth from the distribution function dropped from 21.2 years before the introduction to 19.5 years after the introduction of the technology. In addition, modeling results show that the probability of a woman giving birth to her first child doubles for any age after the introduction of laborsaving technology. However, changes in birth intervals are less conclusive since the differences of smoothed probability distributions are not significant. Moreover, findings indicate that women who initiate reproduction at a younger age can potentially have longer reproductive careers and larger families.     

Comparing the Land Requirements, Energy Savings, and Greenhouse Gas Emissions Reduction of Biobased Polymers and Bioenergy

This study compares energy savings and greenhouse gas (GHG) emission reductions of biobased polymers with those of bioenergy on a per unit of agricultural land-use basis by extending existing life-cycle assessment (LCA) studies. In view of policy goals to increase the energy supply from biomass and current efforts to produce biobased polymers in bulk, the amount of available land for the production of nonfood crops could become a limitation. Hence, given the prominence of energy and greenhouse issues in current environmental policy, it is desirable to include land demand in the comparison of different biomass options. Over the past few years, numerous LCA studies have been prepared for different types of bio-based polymers, but only a few of these studies address the aspect of land use. This comparison shows that referring energy savings and GHG emission reduction of biobased polymers to a unit of agricultural land, instead of to a unit of polymer produced, leads to a different ranking of options. If land use is chosen as the basis of comparison, natural fiber composites and thermoplastic starch score better than bioenergy production from energy crops, whereas polylactides score comparably well and polyhydroxyalkaonates score worse. Additionally, including the use of agricultural residues for energy purposes improves the environmental performance of bio-based polymers significantly. Moreover, it is very likely that higher production efficiencies will be achieved for biobased polymers in the medium term. Biobased polymers thus offer interesting opportunities to reduce the utilization of nonrenewable energy and to contribute to GHG mitigation in view of potentially scarce land resources.     

Non-structural carbohydrate partitioning in grass stems: a target to increase yield stability, stress tolerance, and biofuel production

A dramatic change in agricultural crops is needed in order to keep pace with the demands of an increasing human population, exponential need for renewable fuels, and uncertain climatic changes. Grasses make up the vast majority of agricultural commodities. How these grasses capture, transport, and store carbohydrates underpins all aspects of crop productivity. Sink-source dynamics within the plant direct how much, where, and when carbohydrates are allocated, as well as determine the harvestable tissue. Carbohydrate partitioning can limit the yield capacity of these plants, thus offering a potential target for crop improvement. Grasses have the ability to buffer this sink-source interaction by transiently storing carbohydrates in stem tissue when production from the source is greater than whole-plant demand. These reserves improve yield stability in grain crops by providing an alternative source when photosynthetic capacity is reduced during the later phases of grain filling, or during periods of environmental and biotic stresses. Domesticated grasses such as sugarcane and sweet sorghum have undergone selection for high accumulation of stem carbohydrates, which serve as the primary sources of sugars for human and animal consumption, as well as ethanol production for fuel. With the enormous expectations placed on agricultural production in the near future, research into carbohydrate partitioning in grasses is essential for maintaining and increasing yields in grass crops. This review highlights the current knowledge of non-structural carbohydrate dynamics in grass stems and discusses the impacts of stem reserves in essential agronomic grasses.     

Child health,its dynamic interaction with nutrition and health memory – Evidence from Senegal

Child malnutrition is pervasive in developing countries and anthropometric measures such as weight-for-height and height-for-age have proven reliable indicators of short term malnutrition and stunting. Rather than studying these indicators separately, we look at their interaction and carve out child health dynamics. Considering height-for-age a child's health stock and weight-for-lagged height a proxy for nutritional inputs, we develop a child health production function that features self-productivity of past health stocks and contemporaneous nutritional inputs. We test the model on a Senegalese panel of 271 children between 0 and 5 years employing dynamic panel methods to control for endogeneity in the production function. In line with previous evidence, we find that children can partially catch-up from malnutrition spells. Yet, child health stocks also deplete quickly and need constant updating in the form of nutrition. This demonstrates the importance of health memory and that malnutrition cannot be fought with snapshot interventions. Consequently, sustainable nutrition interventions have to be long term and yield higher returns the earlier they reach children.