Domestic ducks are considered to be an important reservoir of highly pathogenic avian influenza (HPAI), as shown by a number of geospatial studies in which they have been identified as a significant risk factor associated with disease presence. Despite their importance in HPAI epidemiology, their large-scale distribution in monsoon Asia is poorly understood. In this study, we created a spatial database of domestic duck census data in Asia and used it to train statistical distribution models for domestic duck distributions at a spatial resolution of 1 km. The method was based on a modelling framework used by the Food and Agriculture Organisation to produce the Gridded Livestock of the World (GLW) database, and relies on stratified regression models between domestic duck densities and a set of agro-ecological explanatory variables. We evaluated different ways of stratifying the analysis and of combining the prediction to optimize the goodness of fit of the predictions. We found that domestic duck density could be predicted with reasonable accuracy (mean RMSE and correlation coefficient between log-transformed observed and predicted densities being 0.58 and 0.80, respectively), using a stratification based on livestock production systems. We tested the use of artificially degraded data on duck distributions in Thailand and Vietnam as training data, and compared the modelled outputs with the original high-resolution data. This showed, for these two countries at least, that these approaches could be used to accurately disaggregate provincial level (administrative level 1) statistical data to provide high resolution model distributions.
Intensification of animal production can be an important factor in the emergence of infectious diseases because changes in production structure influence disease transmission patterns. In 2004 and 2005, Thailand was subject to two highly pathogenic avian influenza epidemic waves and large surveys were conducted of the poultry sector, providing detailed spatial data on various poultry types. This study analysed these data with the aim of establishing the distributions of extensive and intensive poultry farms, based on the number of birds per holder. Once poultry data were disaggregated into these two production systems, they were analysed in relation to anthropogenic factors using simultaneous autoregressive models. Intensive chicken production was clustered around the capital city of Bangkok and close to the main consumption and export centres. Intensively-raised ducks, mainly free-grazing, showed a distinct pattern with the highest densities distributed in a large area located in the floodplain of the Chao Phraya River. Accessibility to Bangkok, the percentage of irrigated areas and human population density were the most important predictors explaining the geographical distribution of intensively-raised poultry. The distribution of extensive poultry showed a higher predictability. Extensive poultry farms were distributed more homogeneously across the country and their distribution was best predicted by human population density.
Longitudinal studies examining socio-demographic and other contextual factors are vital to understanding landscape change. Landscape structure, function, and change are assessed for the northern Ecuadorian Amazon by examining the composition and spatial organization of deforestation, agricultural extensification, and secondary plant succession at the farm level in 1990 and 1999 through the integration of data from a satellite time-series, a longitudinal household survey, and GIS coverages. Pattern metrics were calculated at the farm level through the generation of a hybrid land use and land cover (LULC) digital classification of Landsat Thematic Mapper (TM) data. Population, labor, and other household variables were generated from a scientific sample of survey farms or fincas interviewed in 1990 and resurveyed in 1999. Topography, soils, and distance and geographic accessibility measures were derived for sample farms through a GIS as well as qualitative assessments from household surveys. Generalized linear mixed models (GLMMs) were generated for 155 and 157 fincas in 1990 and 1999, respectively, using pattern metrics at the landscape level as dependent variables, and biophysical, geographical, and socio-economic/demographic variables as independent variables. The models were derived to explore the changing nature of LULC at the finca level by assessing the variation in the spatial structure or organization of farm landscapes in 1990 and 1999, and the extent to which this variation could be explained by the available data. Results indicate rapid population growth causing substantial subdivision of plots, which in turn has created a more complex and fragmented landscape in 1999 than in 1990. Key factors predicting landscape complexity are population size and composition, plot fragmentation through subdivision, expansion of the road and electrical networks, age of the plot (1990 only), and topography. The research demonstrates that the process of combining data from household surveys, satellite time-series images, and GIS coverages provide an ideal framework to examine population–environment interactions and that the statistical models presented are powerful tools to combine such data in an integrated way.
In a field study, potential adverse effects of Bt maize on plant-dwelling spiders (Araneae) were assessed in 2001 in Bavaria, South Germany. Spider assemblages were recorded in Bt maize fields and conventional maize fields, with and without (pyrethroid) insecticide application. In addition, the efficacy of several sampling techniques to collect plant-dwelling spiders was tested (beating sheets, suction sampling, plant removal, stem eclectors). A total of 29 species and 14 families were identified. Juvenile spiders of the families Theridiidae, Linyphiidae, Tetragnathidae and Araneidae dominated the catch. The sampling methods differed in their capture efficiency with regard to abundance, family composition, species richness and power to detect effects. Suction samplers performed best, and are recommended for monitoring plant-dwelling spiders in maize. Bt maize had no substantial effects on species richness and abundance of spiders, whereas insecticide application reduced spider densities.
The methods currently used for assessing the environmental impact of agriculture on the scale of a farming region cover a wide range of objectives, users and concepts. To illustrate this variety, this article provides an analysis of six main types of method: environmental risk mapping, life cycle analysis, environmental impact assessment, multi-agent system, linear programming and agro-environmental indicators. Eleven case studies, in which one of the six methods was applied, are used as data in this review. All methods are based on a set of environmental objectives. Some methods also take account of economic and social objectives to produce a more wide-ranging assessment of the sustainability of the agricultural system studied. Each method relies on indicators serving as criteria to evaluate whether the objectives have been attained. These indicators take account of local impacts such as noise, regional impacts such as eutrophication, or global impacts like the greenhouse effect. The characteristics required to develop a method for the environmental impact assessment of a farming region are discussed. The analysis of the interactions between farms is indispensable at this scale of analysis. Indicators based on the environmental effects of farming practices should take precedence over those based on the practices themselves, which do not provide a direct evaluation of environmental impact. Indicators which express an impact both per kg of product and per unit of land area used bring together the essential functions of agriculture, namely production and the occupation of the countryside. The assessment methods should include an analysis of the uncertainty associated with the results. Lastly, the method should be validated with respect to (i) the conception of the method and its indicators, (ii) the consistency of the values of the indicators in relation to observed values, and finally (iii) the suitability of the indicators and more generally of the assessment method for the end users.
The objective of this paper is to detect the dominant landscape changes in a 5400 km2 area in northern Ghana. An in-depth analysis of the conventional transition matrix was used to separate landscape transformations to random and systematic transitions. A landscape transition is random if a land-cover category gains from other categories in proportion to the availability of those other losing categories, or if a category loses to other categories in proportion to the size of those other gaining categories. Any large deviation from those proportions is referred to as systematic transition. The highest systematic transition involved the conversion of about 12% of landscape from grassland to cropland. Other systematic landscape transitions included degradation of closed woodland to open woodland (11% of landscape), gain in biomass from open woodland to closed woodland (8% of landscape), and the degradation of open woodland to grassland (6% of landscape). The vulnerability of grassland to transition to cropland probably reflects the ease of clearing grassland compared to other natural vegetation. Cropland systematically avoided gaining from woodland and woodland systematically avoided losing to cropland, suggesting that woodcutting for charcoal and firewood collection is the major proximate cause of decline in woodland. Most of the random landscape transitions occurred in areas affected by spontaneous occupation by migrants, peri-urban cropland expansion as a result of displacement of farmers, and the resettlement of households along the White Volta River after the eradication of water-borne diseases. It is essential to combine systematic and random landscape change analyses for improved understanding of the processes of land use change. This will help in linking patterns to processes and in designing policy interventions aimed at reducing the unfavorable effects of dramatic land change.
A biodiversity-based paradigm for sustainable agriculture is a potential solution for many of the problems associated with intensive, high input agriculture, and for greater resilience to the environmental and socioeconomic risks that may occur in the uncertain future. The challenge is to understand the combined ecological and social functions of agrobiodiversity, determine its contribution to ecosystem goods and services and value for society at large, and evaluate options for the sustainable use and conservation of biodiversity across the agricultural landscape. Agrobiodiversity is most likely to enhance agroecosystem functioning when assemblages of species are added whose presence results in unique or complementary effects on ecosystem functioning, e.g., by planting genotypes with genes for higher yield or pest resistance, mixing specific genotypes of crops, or including functional groups that increase nutrient inputs and cycling. Simply adding more species to most agroecosystems may have little effect on function, given the redundancy in many groups, especially for soil organisms. The adoption of biodiversity-based practices for agriculture, however, is only partially based on the provision of ecosystem goods and services, since individual farmers typically react to the private use value of biodiversity, not the ‘external’ benefits of conservation that accrue to the wider society. Evaluating the actual value associated with goods and services provided by agrobiodiversity requires better communication between ecologists and economists, and the realization of the consequences of either overrating its value based on ‘received wisdom’ about potential services, or underrating it by only acknowledging its future option or quasi-option value. Partnerships between researchers, farmers, and other stakeholders to integrate ecological and socioeconomic research help evaluate ecosystem services, the tradeoffs of different management scenarios, and the potential for recognition or rewards for provision of ecosystem services. This paper considers ways that scientists from different disciplines can collaborate to determine the functions and value of agrobiodiversity for agricultural production, but within the context of understanding how biodiversity can be conserved in landscape mosaics that contain mixtures of land use types.
A sink for atmospheric carbon (i.e., CO2) in soils may derive from the application of conservation tillage and the regrowth of native vegetation on abandoned agricultural land. Accumulations of soil organic matter on these lands could offset emissions of CO2 from fossil fuel combustion, in the context of the Kyoto protocol. The rate of accumulation of soil organic matter is often higher on fertilized fields, but this carries a carbon “cost” that is seldom assessed in the form of CO2 emissions during the production and application of inorganic fertilizer. Irrigation of semiarid lands may also produce a sink for carbon in plant biomass, but its contribution to a sink for carbon in soils must be discounted by CO2 that is emitted when energy is used to pump irrigation water and when CaCO3 precipitates in the soil profile. No net sink for carbon is likely to accompany the use of manure on agricultural lands.
Vesicular-arbuscular (VA) mycorrhizas are widely distributed but there is limited knowledge of the occurrence of individual species in relation to soil, climate and vegetation.Recent developments in methods for identifying and quantifying VAM fungi, both in soil and within roots, should enable the clearer definition of the factors that influence their distribution. Careful attention must be paid to sampling procedures to avoid bias and subjectivity.Soils commonly contain more than one VAM fungus. The development of VA mycorrhizas varies with soil type and depth, season and vegetation. The dynamics of root colonization by individual species within a population have not been adequately explored. Minor or gradual disturbances in agricultural and natural ecosystems may, or may not, lead to marked changes in mycorrhiza formation. Populations of VAM fungi appear to be capable of adjusting to gradual changes in the environment without abrupt changes in the extent of colonization. In contrast, more extreme, or rapid environmental changes such as those associated with mining or erosion, may markedly decrease mycorrhiza formation. The restoration of populations of mycorrhizal fungi will depend on the availability of accessible sources of propagules and on the suitability of the disturbed soils for plant and fungal growth.
The localization of two wild annual Helianthus species recently established in Argentina, H. annuus and H. petiolaris, were found to be connected with climate, soil, and agroecosystem variables. The habitats of both species, being mainly roadsides, were strongly related to disturbance, but they were also found in riparian areas and within crops. Microhabitat conditions allowed clear differentiation among the species’ preferences, H. petiolaris appeared associated with sandy soils with low organic matter content, while H. annuus showed preference for more fertile and fine textured soils. In the western region of the country, irrigation strongly modified the environment favoring H. annuus. No variables allowed characterization of the three sites, where both species grew together.
The soil and vegetation in some areas of the central Pyrenean middle mountains are in poor condition. The main cause of degradation has been identified as soil erosion due to intensive use, including deforestation, overgrazing and extensive agriculture since the Middle Ages, followed by land abandonment starting at the beginning of the 20th century and intensifiying during the early 1950s. In this work, a raster geographical information system (GIS) combined with an expert evaluation system and fallout 137Cs were used to assess soil erosion in the Arnás catchment in the southern Pyrenees, where changes in land use were quite rapid at the beginning of the last century. A soil survey was carried out in the Arnás catchment to identify the soil types and to determine physico-chemical properties related to soil erodibility. A grid pattern was established across the study area and 77 sites were sampled. The GIS was used to integrate the information derived from an automated land evaluation system that, in turn, identified the erosion risk of areas by combining data on various soil properties and physiographic and bioclimatic factors. According to the map of erosion risks generated for the catchment, there were three distinct areas with different soil erosion features where fallout 137Cs was used to assess the soil redistribution pattern. The depth distributions of 137Cs were measured along three transects that represented the three main areas. The 137Cs content in the soils on the shrub slope transect was smallest and significantly different from the deeper and better developed soils on the forest slope, indicating different patterns of soil mobilization. The relationship of some basic soil properties was also examined, such as organic matter and texture, in terms of the patterns of radioisotope distribution and soil erosion. In the catchment, soil redistribution was affected by physiographic and landscape features such as soil properties, slope gradient as well as orientation and vegetation cover. Soil loss was highest along the shrub transect where the rate of soil erosion was much higher than soil formation. Conversely, the soils on the forest transect were mainly stable although some sediment was also deposited. Both aggradation and erosion were found in the valley bottom. The automated evaluation system and GIS used to identify areas vulnerable to erosion combined with the 137Cs technique have proven to be a suitable approach to assess soil erosion aimed to design effective strategies for soil conservation in Mediterranean mountain environments.
Short- and long-term N uptake/partitioning dynamics were studied using stable isotope techniques to investigate the uncertain mechanism(s) of O3 action on plant yield and photosynthate partitioning.Glycine max [L.] Merr.(soybean) plants were grown in 15N enriched soil within open-top chambers and exposed to one of three O3 regimes: half-ambient, ambient, or 2 × ambient. The seasonal 7 h average O3 concentrations (nl l−1) were 25, 43, and 76 nl l−1, respectively. Nitrogen fixation was estimated using the 15N isotope dilution method utilizing a non-nodulating soybean isoline as the control. Macro-kjeldahl technique was used for determining N concentration. Short-term plant responses were investigated by evaluating the following parameters: % N, total N, total N fixed, total N fixed per organ dry weight, the proportion of N-fixed/soil N, and the fraction of N derived through rhizobial N-fixation on an individual organ (leaves, stems, roots, pods, and nodules) and whole plant basis at two reproductive growth stages. Long-term plant responses were investigated by characterizing the same N parameters of the mature grain.Ozone significantly affected both short- and long-term N uptake/partitioning dynamics. Ozone exposure reduced the amount of N derived from N-fixation, but did not significantly affect total N or % N for organs and whole plants. For mature grain, O3 significantly decreased seed yield and all N parameters except N-fixed/soil N, but the responses were dependent upon year.Our results suggest that total nodule activity was affected rather than specific activity. Total N uptake was maintained despite significant decreases in % N-fixed and N-fixed/soil N. We conclude that N-fixation was inhibited by reduced photosynthate translocation to nodules. The photosynthate translocated was sufficient to maintain moderate rates of soil N uptake, but not adequate to maintain high rates of N-fixation, the latter costing more energy. Thus, soybeans damaged by the exposures imposed here, relied more heavily on soil N to meet their total N requirements when photosynthate translocation was inhibited. The long-term negative effects for mature seed also indicate a significant reduction in photosynthate and total N translocated to nodules, and an increased reliance on soil N. In summation, these findings and those of our companion carbon study, support the hypothesis that the mechanism of chronic O3 action involves an inhibition of carbon translocation from leaves to other organs.
Short- and long-term C uptake/transaction dynamics were studied using stable isotope techniques and leaf gas exchange to investigate the mechanism(s) of O3 action on plant yield and C partitioning.Glycine max (L.) Merr. (soybean) plants were grown in open-top chambers and exposed to one of three O3 regimes: half-ambient, ambient, or 2 × ambient for nearly the entire growing season. The seasonal 7 h average O3 concentrations (nl l−1) were 25, 43, and 76 nl l−1, respectively. Whole plant C translocation was measured using pulse-labeled 13CO2 (99 atom %13C) at two distant growth stages (R2 and R5). Translocation parameters were as follows: %13C (sink strength), % 13C/g dry weight (sink intensity), and % 13C/% organ dry weight (relative specific uptake). Single leaf photosynthesis (Pn) was measured at four growth stages (V7, R2, R3, and R4).Ozone significantly affected translocation, but the effect was dependent upon growth stage and the time following the 13C pulse. At the stage of rapid seed fill within the pods (R5), and at 42 h post-labeling, all three leaf translocation parameters had a significant positive linear relationship with O3 exposure. Conversely, root nodule values were all inversely related to O3 exposure. Generally, at 0.5 h post-labeling, no significant effects were observed for leaves and nodule translocation patterns, with the exception of an inverse relationship between sink strength and O3 exposure. No significant differences were observed for single leaf Pn among treatments.Our results indicate that the mechanism of chronic O3 action involves inhibition of translocation, implying reduced phloem loading and the inhibition may be occurring without a concomitant reduction in the amount of C fixed. In addition, 13C pulse labeling appears to be a very useful technique for investigating integrated long-term C translocation dynamics which might not otherwise be evident using instantaneous methods such as short-term labeling or limited leaf gas exchange measurements.
The accumulation of P originating from animal wastes in the soil profile is of agronomic and environmental concern. Sequential extraction procedure provides relevant information to mobility, bioavailability and distribution of P in animal manure-amended soils. Such information is needed to assess the potential for biological P leaching, under organic amendments, in some Quebec agriculture ecosystems. This study was conducted using soil samples from the long-term experimental plots of the Soil Research Station of the Quebec Ministry of Agriculture, Fisheries and Food at St-Lambert de Lévis, Quebec, Canada. The objective of this work was to examine the distribution of P fractions in the profile of a Le Bras silt loam soil (Gleysol) growing corn (Zea mays L.) which had received liquid pig manure (LPM) for 14 years. The surface soil was fertilized annually with various rates of LPM (0, 30, 60, 90 and 120 cm3 ha−1) in a randomized complete block design with four replicates since 1979. In the fall of 1992, soil samples were collected after the corn harvest from 20 soil plots at 20-cm intervals to a depth of 100 cm. Soil samples were air-dried, crushed, sieved through a 2-mm sieve, and analyzed for soil P fractions using a sequential extraction technique. All treatments resulted in an increase in the labile P pool contents of surface or profile soil compared with the control. Without exception, the amounts of P pools decreased with soil depth and were highly correlated with the LPM rates. The proportion of total P as labile (resin-Pi + NaHCO3-P + NaOH-P) in the soil profile increased from 61 (control) to 79% (highest LPM rate). The amounts of P generally increased in the following order: moderately labile NaOH-Pi and -Po (254 mg kg−1) > labile P extracted by resin and NaHCO3 (209 mg kg−1) > stable P (172 mg kg−1). On average, the amount of labile Pi forms (304 mg kg−1) was larger than the amount of labile Po forms (159 mg kg−1) and represented an important fraction of the total labile P pools. Compared to the control treatment, the mean concentration of geochemical P (resin-Pi + NaHCO3-Pi + NaOH-Pi + HCl-Pi + residual P) increased in the soil profile by 16, 26, 33 and 50% for 30, 60, 90 and 120 m3 ha−1 LPM, respectively. On a profile basis, the soil receiving the highest rate of LPM contained 1.8-fold the biological P (NaHCO3-Po + NaOH-Po) of the unamended soil. Amounts of labile Po pools in the soil profile were highly correlated with the organic carbon content. Results from this study suggest that heavy application of LPM over the 14-year period promotes P movement to lower portions of the soil profile. The leaching or translocation of P compounds would be responsible for the distribution of P in the various soil layers. Management of LPM rates is necessary after a long-term fertilization of corn.
Differences between conventional and sustainable paradigms of agriculture are much more a matter of differences in farming philosophy than of farming practices or methods. The conventional model of agriculture is fundamentally an industrial development model which views farms as factories and considers fields, plants, and animals as production units. The goal of industrial development is to increase human well-being by increasing production of material goods and services and simultaneously increasing aggregate employment and incomes. The underlying assumption of the industrial model is that a higher quality of life can be derived from increases in income and consumption of goods and services. A fundamental strategy for industrial development has been to specialize, routinize, and mechanize agricultural production in order to achieve the economic effeciencies that are inherent in large-scale industrial production. New technologies are designed to remove physical and biological constraints to production and, thus, make unlimited progress possible. Sustainable agriculture, on the other hand, is based on a holistic paradigm or model of development which views production units as organisms that consist of many complex interrelated suborganisms, all of which have distinct physical, biological, and social limits. People are viewed as part of the organisms or systems from which they derive their well-being. Quality of life is considered to be a consequence of interrelationships among people and between people and the other physical and biological elements of their environment. Fundamental strategies for sustainable development include diversification, integration, and synthesis. Whole systems have qualities and characteristics that are not contained in their individual parts or components. The same set of components or parts may be rearranged spatially or sequentially resulting in a unique system or whole for each new arrangement. People increase their well-being by using information and knowledge to manage or rearrange the components of systems, resources, processes, and technologies in ways that enhance the productivity or ‘well-being’ of those systems. Human progress is limited only by our ability to enhance the social, biological, and physical systems of which we are a part. Sustainable agriculture requires a holistic systems approach to farm resource management. A component approach focusing on individual farming practices, methods, and enterprises may have been appropriate for the era of agricultural industrialization. However, a systems approach which focuses on knowledge-based development of whole farms and communities will be required to address the environmental, economic, and social challenges of the post-industrial era of agricultural sustainability.
Long-term productivity and conservation of soils is critical for sustaining agricultural ecosystems. Long-term sites can provide important information about the effects of soil management practices on soil properties but there are relatively few such sites available worldwide. The Colca Valley of Peru provided a unique opportunity to study the effects of 1500 years of cultivation on Mollisols. The specific objective of the work reported was to determine the effects of cultivation at this site on soil enzyme activity as an index of soil biology and biochemistry. The study compared three key soil enzyme activities (phosphatase, β-glucosidase, and amidase) in presently cultivated and abandoned agricultural terraces, and matched uncultivated soils. Results showed that levels of organic matter, nitrogen and phosphorus were greater in agricultural than uncultivated soils. Unlike temperate regions where monoculture, intensive tillage and/or inorganic fertilizer practices have depressed soil enzyme activities, cultivated Colca soils have maintained similar or higher activities than the uncultivated/native soils. Maintenance of enzyme activities over hundreds of years in agricultural soils is partly attributed to traditional management practices including rotations with legumes, additions of animal manures, and minimum tillage.
An isotope dilution method for measuring biologically active soil nitrogen (ASN) was developed. It involved insertion of 15N into the soil N cycle and stimulation of microbial activity until added 15N was mixed with the ASN pool. Both glucose addition (GLU) and glucose addition-CHCl3 fumigation (GFU) were used to promote mixing. Experimental tests with model systems provided evidence that isotopic mixing can be achieved. Because the concept of a discrete pool is an approximation, the ASN pool was operationally defined as the measured after a 40-day incubation at 22°C. The GLU treatment was gave lower ASN values than the GFU treatment, probably because fumigation killed microorganisms not responding to glucose addition. Microbial biomass was estimated to contribute 23–48% and 34–77% of the N in the ASN pool in a wheat field and a long-term pasture, respectively, depending upon the method of calculation of microbial biomass N. ASN values in these same fields showed depth patterns consistent with tillage and cropping histories. About 40% of fertilizer-derived organic 15N remaining in soil following growth of a wheat crop was determined to be in the ASN pool, which is similar to potentially mineralizable values found in other 15N studies.
The recovery by spring barley (Hordeum vulgare L.) of nitrogen mineralized from 15N-labelled straw and ryegrass material was followed for 3 years in the field. The effects of separate and combined applications of straw and ryegrass were studied using cross-labelling with 15N. Reference plots receiving 15NH415NO3 were included. Plant samples were taken every second week until maturity during the first growing season and at maturity in the two following years.Incorporation of plant material had no significant influence on the above-ground dry matter yield of the barley. The barley recovery of N derived from straw was not significantly different whether straw was incorporated alone or in combination with ryegrass material. The mean recovery of straw N was 4.5% in the first barley crop and 2.7% and 1.1% in the second and third crop.During the first growing season, recovery of ryegrass N in the barley was higher when the catch crop material was incorporated without straw, but the differences were only significant at one sampling date. At maturity 7.8% and 10.2% of the ryegrass N was recovered in the barley crop, when ryegrass was incorporated with or without straw, respectively. Mean recoveries of ryegrass N were 2.3% in the second year and less than 1% in the third year after incorporation.recovery of mineral fertilizer in the year of application was relatively low (29–40%), probably due to long periods of spring drought in all 3 years. The recovery of N from residual mineral fertilizer was in the second and third barley crop similar to the recovery of N from incorporated plant residues.
A field study was conducted to determine the effects of gypsum and phosphogypsum on methane and nitrous oxide evolution and on 15N and 226Ra uptake by Oryza sativa L. (rice). Gypsum and phosphogypsum at 2.5, 5.0 and 10.0 tons ha−1 and 15N labelled urea (150 kg N ha−1) were applied pre-flood to experimental plots drill-seeded with `cypress', a semi-dwarf long-grain rice cultivar. Methane and nitrous oxide were measured twice a week over the main cropping season. Plant samples were collected at harvest and 15N uptake and 226Ra activity measured. Three rates of gypsum reduced methane evolution 49, 52 and 66%, respectively, compared with control plots. Phosphogypsum (2.5, 5.0 and 10.0 tons ha−1) decreased emissions of methane 47, 46 and 51%, respectively, over the 84-day study. Nitrous oxide fluxes were low (10–29 g ha−1 day−1) and only detected from control plots on two sampling dates. The assimilation of applied 15N in grain collected from gypsum plots was significantly higher compared with control and phosphogypsum treatments. The measured grain 226Ra activities were low and averaged 0.518 Bq kg−1 for phosphogypsum compared with a control plot activity of 0.222 Bq kg−1.
Conversion of pastures to plantation forests has been proposed as a means to increase rates of carbon (C) sequestration from the atmosphere thereby reducing net greenhouse gas emissions from human activities. However, several studies have indicated that soil C stocks decrease after planting conifer (mainly pine) trees into pasture. This loss of soil C detracts from the role that plantation forests can play in net C sequestration. Here, we used a paired site (a grazed native pasture with the C4 grass Themeda triandra dominant, and an adjacent 16-year-old Pinus radiata plantation) to compare all C and nitrogen (N) pools (including soil, litter on the floor, below-ground and above-ground biomass) in the two ecosystems and to estimate the rate of C sequestration after the land use change from the native pasture to the pine plantation. Soil C and N stocks from soil surface down to 1 m under the pine plantation were significantly less than under the native pasture by 20% (57.3 Mg C ha−1 vs. 71.6 Mg C ha−1) and 15% (5.6 Mg N ha−1 vs. 6.7 Mg N ha−1), respectively. Much more C and N was stored in litter on the floor in the pine plantation than in the native pasture (8.0 Mg C ha−1 vs. 0.03 Mg C ha−1, and 119.0 kg N ha−1 vs. 0.9 kg N ha−1), and in biomass (95.0 Mg C ha−1 vs. 2.5 Mg C ha−1 and 411.5 kg N ha−1 vs. 62.8 kg N ha−1). Carbon stored in coarse tree roots was alone sufficient to compensate the C loss from soil after the land use change. Much more C and N was deposited annually to above-ground litter in the pine plantation than in the native pasture (2.18 Mg C ha−1 year−1 vs. 0.22 Mg C ha−1 year−1, and 32.8 kg N ha−1 year−1 vs. 5.9 kg N ha−1 year−1), but less to below-ground litter (through fine root death) (2.71 Mg C ha−1 year−1 vs. 3.57 Mg C ha−1 year−1 and 38.9 kg N ha−1 year−1 vs. 81.4 kg N ha−1 year−1). The shift in net primary production from below-ground dominance to above-ground dominance after planting trees onto the pasture, and the slower turnover of litter in the plantation, played a key role in the reduction in soil C in the plantation ecosystem. In conclusion, planting pine trees onto a native temperate Australian pasture sequestered a significant amount of C (net 86 Mg C ha−1, averaging 5.4 Mg C ha−1 year−1) from the atmosphere in 16 years despite the loss of 14 Mg C ha−1 from the soil organic matter.
Land use in general and particularly agricultural practices can significantly influence soil carbon (C) storage. Changes in topsoil C mass measured in long-term agricultural field trials in Sweden and other Northern European countries were compiled and aggregated into seven treatment classes, including manured, fertilized and straw exported. The impact of crop rotations and management practices on C stocks in the topsoil was analyzed using both a static model and a dynamic soil carbon model (introductory C Balance Model; ICBM). ICBM consists of two state variables and four fluxes (governed by four rate-determining parameters), and one parameter, re, combining most external factors affecting C mineralization (temperature, precipitation, drainage, etc.). Simple `front-end models' were used to estimate values for two of the parameters, i (annual C input) and h (humification coefficient) initially based on incomplete records from the field trials, official agricultural statistics and other literature. The re parameter was then optimized for each class of treatments, using an algorithm for non-linear least squares. Initial soil C mass, present C inputs and abiotic conditions, such as soil temperature and moisture, were the deciding factors in whether C stocks declined or increased. Steady-state values calculated using the static and dynamic model were similar for both models, but differed greatly between treatment classes. For cereal-dominated cropping systems where the straw was removed, manure application increased steady-state values about three times (from 3 to 9 g C m−2), compared with corresponding treatments. Incorporation of straw resulted in intermediate steady-state values (5–6 g C m−2). C mineralization rates were highest in bare fallow treatments. For one class of soils, C retention in the soil was found to increase significantly with increasing clay content. The hypothesis that the climatic gradients in Northern Europe affect decomposition and primary production rates similarly, leading to the same soil C stocks, could not be rejected.
Long-term migration and crop uptake of cadmium (Cd) were investigated in a cultivated field experiment, that had been started 41 years earlier on a structured clay loam. One treatment was supplied biennially with digested sewage sludge and PK-fertilizer, while the control received calcium nitrate and PK-fertilizer. The estimated total Cd supply was ca 153 and 13 mg Cd m−2 in the sludge and control treatments, respectively. In the sludge treatment, 92% of applied Cd was recovered in the topsoil and 7% in the upper 17 cm of the subsoil. The total loss of Cd out of the profile was negligible after 41 years, even though increases in dissolved organic carbon (DOC) concentrations were observed throughout the profile. Thus, macropore transport of Cd, either as Cd2+ or complexed by DOC was apparently not significant. This was attributed to the strong sorption capacity of the arable soil and incorporation of the sludge into the soil matrix, thereby increasing the contact of sludge-borne Cd to soil particles and protecting the Cd from transport in macropores. Cd solubility in equilibrium extracts of Ca(NO3)2 increased by a factor of 20 in the sludge treatment compared to the control. This was reflected in the Cd concentration of the straw fraction in barley, which was almost doubled in the sewage sludge treatment. The grain fraction showed, however, no significant increase in Cd concentration. As crop biomass increased as a consequence of sewage sludge supply, the Cd offtake in harvest was more than twice as high compared to the control. The sewage sludge applications did not pose a high risk for leaching losses of Cd in this soil, but resulted in increased Cd concentrations in the straw fraction.
The role of indigenous vertebrate predators, especially birds, in controlling pest insects is poorly known. This study quantifies the effectiveness of helmeted guineafowl Numida meleagris (Linnaeus 1766; Aves: Numididae) in controlling the banded fruit weevil Phlyctinus callosus (Schönherr 1826; Coleoptera: Curculionidae), a pest in apple and nectarine orchards in the Western Cape Province, South Africa. The impact of guineafowl on other invertebrates and on apple crops is also assessed. Periodic counts of weevils under trunk bands showed that guineafowl did not reduce weevil numbers significantly, but suction samples indicated that weevils were more abundant in plots without guineafowl. On average only 1.07 weevils were found in 30 guineafowl crops (range 0–14 weevils). The results suggest that although guineafowl consume weevils, they have a negligible impact on large weevil populations. Other invertebrates, especially molluscs and elaterid larvae (Coleoptera) were often eaten. Guineafowl reduced insect diversity in apple orchards either directly through predation or indirectly by altering the structure of the cover plants. The damage that guineafowl allegedly cause to apples was not confirmed.
Hunting records indicate a decline in the populations of the European brown hare (Lepus europaeus) in the early 1960s. This paper summarises the likely reasons for the population decline. The emphasis on wildlife incident reports and paraquat is in response to the perception that it may present a risk to hares. The possibility for early incidents of European Brown Hare Syndrome (EBHS) being misdiagnosed as paraquat incidents are also considered.The long-term decline in the hare population throughout Europe is widely believed to be due to changes in farmland management practices, resulting in the loss of crop/landscape diversity which affects nutrition. Predation and disease may lead to additional high mortality but probably do not influence the long-term population trend.The decline in the hare population in England, as in Europe, started prior to the widespread introduction of paraquat. Wildlife incident schemes in the UK (WIIS) and France (SAGIR) confirm there have been very few hare deaths caused by paraquat. Research indicates that free living hares are likely to be deterred from foraging paraquat sprayed vegetation after an initial exposure.
To prevent or prepare for future food shortages an understanding of the likely magnitude and distribution of future cereal yields is required. To this end, predictions of cereal yields have commonly been made, using various assumptions. However, the employed assumptions, namely, that yields tend to follow a given trend over time, have not been extensively tested. This study presents a test of the applicability of two general models to time series of maize (Zea mays L.), rice (Oryza sativa L.), and wheat (Triticum aestivum L.) yields for 188 nations to characterize past yield trends, to assess the relative importance of various trends on a global scale, and lastly, to determine what factors might be responsible for the presence of slowing yield growth and yield decline in some nations. Results showed that linear growth in yields has been the most common trend over time, occurring in more than half of all nation-crop data sets, and that growth significantly greater than 33.1 kg ha−1 yr−1 (the rate at which global cereal yields must grow to have the current per-capita production in 2050) constituted 20% of the data sets and was the most important trend in terms of global area harvested, production, and population. A trend of slowing yield growth was present in roughly one-sixth of the data sets, and the nations that this subset comprised made a small contribution to global area harvested, production, and population (less than 10%). Nation-crop data sets that showed yield growth greater than 33.1 kg ha−1 yr−1 had much greater yields than those that showed slowing yield growth, demonstrating that yield growth is not being limited by general physiological constraints to crop productivity. The results of a logistic regression procedure showed that the relative frequency of slowing yield growth and yield decline was negatively correlated to per-capita gross domestic product (GDP) for maize and wheat, and to growth in fertilizer rate for maize. In addition to GDP, latitude was negatively correlated with the relative frequency of yield decline. There were no significant predictors for rice. These results suggest that both economic and biophysical factors have played a role in limiting cereal yield growth.
While tropical multistrata home gardens (or tree home gardens) are classically said to be sound, efficient and sustainable land-use systems, there is little quantitative evidence and detailed analysis of home gardens in the literature to support this. In order to strengthen the basis of this assumption and to contribute to an operational understanding of sustainability, a literature review was applied to home gardens, covering different bio-physical and socio-economic conditions. For this, a series of sustainability descriptors were identified, hypothesis formulated on what should be the effect of home gardens on these descriptors, and possible indicators confirming the hypothesis mentioned, when found in the literature.Home gardens possess a number of sustainability attributes, with regard not only to their ability to meet a number of farmers' needs without negatively affecting the resource base, and in many cases even improving it, but also to their potential to meet several economic, social, ecological and institutional conditions which contribute to their sustainability.
Increasingly research suggests that the level of internal regulation of function in agroecosystems is largely dependent on the level of plant and animal biodiversity present. In agroecosystems, biodiversity performs a variety of ecological services beyond the production of food, including recycling of nutrients, regulation of microclimate and local hydrological processes, suppression of undesirable organisms and detoxification of noxious chemicals. In this paper the role of biodiversity in securing crop protection and soil fertility is explored in detail. It is argued that because biodiversity mediated renewal processes and ecological services are largely biological, their persistence depends upon the maintenance of biological integrity and diversity in agroecosystems. Various options of agroecosystem management and design that enhance functional biodiversity in crop fields are described.
Carbon (C) input from tree prunings and crop residues help to maintain the soil organic C pool in tropical agroforestry systems. This study quantified the C stock of tree roots and C input from tree prunings and crop residues in 19-, 10- and 4-year-old Erythrina poeppigiana and Gliricidia sepium alley cropping systems in Costa Rica. The 19-year-old alley cropping system was studied at two fertilizer levels (tree prunings only [−N], and tree prunings plus chicken manure [+N]), and was compared to a sole crop. The 10- and 4-year-old systems were also studied at two fertilizer levels (tree prunings only [−A], and tree prunings plus Arachis pintoi as a groundcover [+A]), and compared to a sole crop. In the 19-year-old system C input from G. sepium was significantly greater (P < 0.05) compared to E. peoppigiana, but for both tree species there was no significant difference between +N and −N treatments. For the 10- and 4-year-old systems, E. poeppigiana had a significantly higher (P < 0.05) C input from prunings compared to G. sepium, and the presence of A. pintoi increased pruning biomass productivity significantly in these systems. Tree roots of 10- (4527 kg C ha−1) and 4-year-old (3667 kg C ha−1) E. poeppigiana represented 16 and 28% of the total C allocation. Carbon input from maize (Zea mays L.) and bean (Phaseolus vulgaris L.) residues were not significantly different (P < 0.05) between alley crops and sole crops in the 19-year-old system per unit of cropped land. In this system, +N treatments had a significantly greater (P < 0.05) C input from bean residue than in −N treatments, but no such trend was observed for maize residues. Carbon input from maize and bean residues were significantly greater (P < 0.05) in alley crops than the sole crops, but not significantly different (P < 0.05) between +A and −A treatments in the younger system. The greatest input of organic material occurred in the 19-year-old alley crop followed by the 10- and 4-year-old alley crops. This additional input of organic material in alley crops, mostly derived from tree prunings, will help to maintain or increase the level of the soil organic carbon pool.
Invasive pasture weeds are often believed to have detrimental effects in managed pastures, but little is known as to the nature of these effects. We investigated the impact of the invasive weed species Senecio jacobaea L. (ragwort) on various aspects of a pasture ecosystem in the Waikato area of New Zealand. S. jacobaea plants often enhanced total pasture production in their immediate vicinity, probably through improving microclimatic conditions, and these effects continued for several months after plant death. Lolium perenne L. (perennial ryegrass) was generally stimulated by S. jacobaea, while Trifolium repens L. (white clover) was inhibited by flowering S. jacobaea plants and various weedy species showed a mixed response. Nitrogen fixation by T. repens (measured by acetylene reduction bioassay) was generally unresponsive to S. jacobaea plants but some temporary enhancement was observed around the edges of individual flowering plants. The soil microbial biomass (biomass of microbes responsible for nutrient cycling) and saprophytic microarthropods were both reduced in the area immediately adjacent to flowering S. jacobaea plants, and this appeared to be negatively related to the enhanced production of pasture (especially L. perenne) in this zone. S. jacobaea plants also exerted some effects on soil macrofauna captured in pitfall traps. Addition of nitrogen- and phosphorus- based fertilisers in general did not alter the nature of the interactions we observed. Based on our results for S. jacobaea it would appear that invasive weeds may have a wide range of consequences in pasture ecosystems and these need to be acknowledged before the overall impact of weeds in pastures can be understood.
Industrial agriculture relies on large quantities of fossil fuels and electricity. The increase in energy prices in the 1980s prompted substantial investigation into the response of farmers to new energy conditions, and into the prospects for future food production in the face of scarcer and more expensive energy inputs. Previous attempts to model these relationships were hampered by a lack of consistent and reliable historical data on total energy use in USA agriculture. This analysis develops and applies a new methodology to calculate the direct and indirect use of fossil fuels and electricity on USA farms from 1910 to 1990. The data on energy use is used to construct indices of energy productivity over the same period. The results show a substantial overall increase in energy use from 1910 through the 1970s, and a shift from gasoline to diesel fuel and electricity. The use of all fuels declined in the 1980s. The measures of energy productivity show a substantial decline in through the 1970s, a trend consistent with the substitution of fossil fuels for animate power and with the low price of fossil fuels relative to other inputs. Energy productivity rose in the 1980s due to a diminution in the rate of energy use, a reduction in the number of harvested hectares, and larger farms. The results show a clear response of farmers to higher energy prices that resulted in technical and managerial changes that improved energy productivity.
Land-use and land-cover change can play a pivotal role in environmental changes. Using aerial photos and spot satellite image on two nearby but different agroecological zones of the Kenyan highlands, an extensive semi-arid area in the lower zone and a humid area in the upper zone, significant land-use changes were identified between 1958, 1985 and 1995. These land-use changes were observed through a photo-interpretation of photos and image with a common classification scheme. The pattern and the development of land-use change differed markedly over the 40-year period between the upper and the lower zone. The introduction of cash-crops had a significant impact on the land-use in the upper zone. Tree plantations whose lines characterize the present landscape came with the switch to cash-crops. In contrast, although no significant land-use changes occurred between 1958 and 1985 in the lower zone, the changes over the last 10 years were significant, with a 75 % increase in cultivated land area. Part of these land-use changes can be explained by strong links between the two zones, as the lower zone became an outlet for the very high population density of the upper zone. This study is a first step for an in-depth characterization of the various driving forces and for land-use planning in these Kenyan highlands.
Landscape changes during 1954–1998 in the districts of Toholampi, Nurmijärvi and Liperi, in west, south and east Finland, are described in relation to agricultural modernization. The following landscape indices are used to analyze development in these areas from the viewpoint of landscape ecology: Shannon’s evenness (SHEI), patch density (PD), edge density (ED) and percentages of land use composition (%LAND). Variables describing modernization and the numbers of farms and tractors are measured in relation to field area. Changes in distribution among patches were indicated to be decreasing. Changes in patch densities and edge lengths imply noticeable simplifications of the visual landscape. Surprisingly, the areas of the buffer zones in Toholampi and Nurmijärvi increased steadily during the period concerned. At the same time, two-thirds of the farms gave up agriculture and field sizes per farm trebled. In addition, in all three areas there was not more than an average of 8.7 ha field area per tractor in 1998, a decline from 265 ha per tractor in 1950, reflecting agricultural mechanization. Thus socio-economic changes imply changes in the local farming culture and need to be considered together with the level of landscape diversity.
During the last 50 years, mechanisation of the rural environment, and, more recently, the Common Agricultural Policy have led to profound changes in agrarian landscapes throughout Europe, and in particular in the rich and diverse Mediterranean landscapes (Meeus et al., 1990). In the north-east of the Iberian Peninsula, a small area of hedgerow landscape persists as a remnant of what was once an important centre for livestock production. This paper presents the results of a study carried out in this area with the aim of clarifying the relationship between the structural change of this hedgerow landscape and the evolution of farming practices developed by its owners and workers. It also considers these farmers’ perceptions of their pastures, of their farms and of the region. Up to 61 statistically significant relationships were found between the physical landscape characteristic variables and the socio-economical variables. Results depict a hedgerow landscape determined by the combination of two management models. Here, and contrary to conclusions reported in similar literature, traditional pasture activity leads to a weaker hedgerow network than a farming model based on crop cultivation. Management guidance required to move from the current situation towards a hedgerow landscape supporting both biodiversity and agrarian activity is discussed.
Land use change in China is related closely to global environmental change and global food security. In this paper, we analyzed land use change for rice, wheat and maize production in China during 1961–1998 based on long-term historical data. The results indicated that the total land area planted for cereals had both increased and decreased between 1961 and 1998. The total area in cereals increased or remained unchanged during 1961–1978, a period when the “Cultural Revolution” occurred, and also increased during 1986–1990 when the Chinese government increased subsides to agriculture. However, the total area in cereals declined during 1980–1985, a period corresponding to the implementation of the “household responsibility system” policy, and during 1991–1995, when a large proportion of the rural labor force moved to urban areas. The center of cereal production has moved towards northern China although the major area planted for rice, wheat and maize together is still located in southern China. The yield per hectare for all crops has increased from 1.21 t/ha in 1961 to 4.83 t/ha in 1998, but the yield per unit chemical fertilizer use decreased from 164 (rice), 44 (wheat) and 93 (maize) kg/kg in 1961 to 10 (rice), 6 (wheat) and 9 (maize) kg/kg in 1998. The increases in yield per hectare and production per capita appear mostly due to the increased industrial energy inputs, especially the rapid increase in chemical fertilizer use after the “household responsibility system” in late 1970s. The decline of the yield per unit chemical fertilizer use appears as a result of fertilizer saturation, soil degradation, soil and water pollution, the shortage of irrigation in the north, the threat of flooding in the south, and poor and low quality land use, as well as other social, economic and technical issues. With limited reclaimed land resources remaining and a near saturation in the response of crops to fertilizers, increasing food demand from the increasing population will have to come mainly from increased land productivity that will almost certainly continue to lead to the decline of energy (e.g. fertilizer) use efficiency and continued environmental degradation. Alternatively China may begin to import large amounts of food. This situation will generate adverse effects on sustainable development in China, as well as food security in the world, especially if world energy is in short supply.
The distribution of six species of birds known to depend on extensive pastoral systems, as published in atlases of breeding birds, was mapped in Britain for two time periods: 1968–1972 and 1990–1992. The species chosen (corncrake Crex crex, golden eagle Aquila chrysaetos, hen harrier Circus cyaneus, stone curlew Burhinus oedicnemus, chough Pyrrhocorax pyrrhocorax and red-backed shrike Lanius collurio) are known to be declining or vulnerable across large parts of their European range. Summed species distribution was compared with available data on the distribution of low intensity agricultural land in Britain. In 1990, bird and land-use distribution was similar. Thus it is concluded that it may be possible to use summed species distribution to predict areas where ecologically beneficial farming systems exist elsewhere in Europe.Most coincidence in species distribution now occurs in Scotland, northern England and Wales. However, large parts of mid-west Scotland have less selected pastoral species than in 1968–1972. The most obvious changes have occurred throughout East Anglia, the south-east and south-west of England. There has been significant fragmentation of coincidence along the north Norfolk coast and along the coasts of Suffolk and Essex.The extent of summed distribution of the indicator bird species chosen declined and fragmented dramatically between 1970 and 1990. There was a significant negative relationship between livestock units per hectare (both sheep and total), and mean species coincidence (average number of species occurring in each 10km2) for six regions in Scotland and northern England in 1990. In each of these six regions, mean species coincidence declined as sheep livestock units per hectare increased between 1970 and 1990.The need for changes to agricultural policies at the level of the European Community in order to reverse this serious conservation problem, is discussed.
The Global Environment Facility co-financed Soil Organic Carbon (GEFSOC) Project developed a comprehensive modelling system for predicting soil organic carbon (SOC) stocks and changes over time. This research is an effort to predict SOC stocks and changes for the Indian, Indo-Gangetic Plains (IGP), an area with a predominantly rice (Oryza sativa)–wheat (Triticum aestivum) cropping system, using the GEFSOC Modelling System and to compare output with stocks generated using mapping approaches based on soil survey data. The GEFSOC Modelling System predicts an estimated SOC stock for the IGP, India of 1.27, 1.32 and 1.27 Pg for 1990, 2000 and 2030, respectively, in the top 20 cm of soil. The SOC stock using a mapping approach based on soil survey data was 0.66 and 0.88 Pg for 1980 and 2000, respectively. The SOC stock estimated using the GEFSOC Modelling System is higher than the stock estimated using the mapping approach. This is due to the fact that while the GEFSOC System accounts for variation in crop input data (crop management), the soil mapping approach only considers regional variation in soil texture and wetness. The trend of overall change in the modelled SOC stock estimates shows that the IGP, India may have reached an equilibrium following 30–40 years of the Green Revolution. This can be seen in the SOC stock change rates. Various different estimation methods show SOC stocks of 0.57–1.44 Pg C for the study area. The trend of overall change in C stock assessed from the soil survey data indicates that the soils of the IGP, India may store a projected 1.1 Pg of C in 2030.
Sustainability has become an important discussion topic across the world since the late 1980s. However, there is still lack of knowledge about the landscape sustainability and its quantitative evaluation, especially at local and regional scale levels. The sustainable development of the Chinese Loess Plateau has always been a focus in China mainly because of the occurring severe soil erosion. This study investigates the changes of the landscape pattern and the changes of the ecological sustainability of the agricultural landscapes in Ansai County between 1980 and 2000, which is located in the northern part of the Chinese Loess Plateau. Using a landscape typology as a spatial reference framework, the concept of hemeroby was used, in a multidisciplinary approach, for the assessment of the ecological aspect of agricultural landscape sustainability. We combined expert judgement with a regression model and a Geographic Information System. Fourteen variables describing the landscape structure were chosen as predictors for hemeroby. The research showed that the major changes in the agricultural landscape pattern were caused not only by socio-economic factors but also by the government policies over the past two decades, such as the large-scale eco-environment conservation programmes starting in the late of the 20th century. One of these programmes is known as the Grain-for-Green Programme (initiated in 1999). Between 1980 and 2000, the proportion of cropland-dominated landscape sharply decreased while the percentage of the mixed farmland–grassland landscape and the mixed farmland–woodland–grassland landscape increased. Meanwhile, the ecological sustainability of the agricultural landscape as a whole tended to become more sustainable, except a few landscape types. Among variables describing landscape pattern, patch size standard deviation (PSSD), total edge (TE), mean shape index (MSI), landscape shape index (LSI) and Shannon's evenness index (SEI) were shown to be the significant predicators for hemeroby. Although some data limitation, landscape structure turned out to be a good predicator for land use intensity and ecological sustainability of agricultural landscape estimated by hemeroby. As a highly integrative indicator, the concept of hemeroby provides a framework for the comparison of different land use pattern.
The Dutch Programme on Soil Ecology of Arable Farming Systems is evaluated in terms of scientific results, feasibility of integrated arable farming and future research needs. It is concluded that the knowledge obtained on the role of the soil biota in the functioning of the soil-crop ecosystem is a prerequisite for the further development of reduced-input farming systems. This knowledge should be integrated with experimental and modelling studies on soil organic matter dynamics and crop growth.
Between 1990 and 2000, farmland birds showed a significant decline across Europe, a trend not shared by bird assemblages of other habitats over the same period. Mean trends for each farmland species in the period 1990–2000 were positively correlated with trends over the period 1970–1990, and there was little change in population trajectory for most species over the 30-year period. Of the 58 species classed by an independent assessment as being primarily birds of farmland, 41 showed negative overall mean trends across Europe in 1990–2000, 19 of them significant. There was a significant negative correlation between mean national trends of all farmland species and indices of national agricultural intensity. This relationship strengthened when the 19 declining species were considered alone, and was not apparent when only non-declining species were considered. Population trends of terrestrial non-farmland bird species over the same period were unrelated to agricultural intensity. Trends in farmland bird populations were independent of the proportion of farmland under agri-environment prescriptions. The results support earlier evidence that population trends of farmland birds across Europe can be predicted from gross national agricultural statistics. Substantial changes in agricultural policy, particularly the removal of economic incentives that lead to agricultural intensification, are required if 2010 targets for halting loss of biodiversity are to be met in an enlarged European Union.
Under the United Nations Framework Convention on Climate Change (UNFCCC), Non-Annex 1 countries such as Kenya are obliged to report green house gas (GHG) emissions from all sources where possible, including those from soils as a result of changes in land use or land management. At present, the convention encourages countries to estimate emissions using the most advanced methods possible, given the country circumstances and resources. Estimates of soil organic carbon (SOC) stocks and changes were made for Kenya using the Global Environment Facility Soil Organic Carbon (GEFSOC) Modelling System. The tool conducts analysis using three methods: (1) the Century general ecosystem model; (2) the RothC soil C decomposition model; and (3) the Intergovernmental Panel on Climate Change (IPCC) method for assessing soil C at regional scales. The required datasets included: land use history, monthly mean precipitation, monthly mean minimum and maximum temperatures for all the agro-climatic zones of Kenya and historical vegetation cover. Soil C stocks of 1.4–2.0 Pg (0–20 cm), compared well with a Soil and Terrain (SOTER) based approach that estimated ∼1.8–2.0 Pg (0–30 cm). In 1990 48% of the country had SOC stocks of <18 t C ha−1 and 20% of the country had SOC stocks of 18–30 t C ha−1, whereas in 2000 56% of the country had SOC stocks of <18 t C ha−1 and 31% of the country had SOC stocks of 18–30 t C ha−1. Conversion of natural vegetation to annual crops led to the greatest soil C losses. Simulations suggest that soil C losses remain substantial throughout the modelling period of 1990–2030. All three methods involved in the GEFSOC System estimated that there would be a net loss of soil C between 2000 and 2030 in Kenya. The decline was more marked with RothC than with Century or the IPCC method. In non-hydric soils the SOC change rates were more pronounced in high sandy soils compared to high clay soils in most land use systems.
In order to assess possible changes in occurrences of pests and diseases in winter wheat as a result of differences in farm management, a monitoring study was carried out between 1993 and 1997 in The Netherlands to assess pest and disease incidence in winter wheat produced by conventional, integrated and organic methods. For the characterization of the different management types and for the interpretation of differences in pest and disease levels among management types information was gathered by yearly questionnaires on field characteristics, crop rotation, tillage, seeding, fertilizers, growth regulators, fungicides, insecticides and weed control in 558 fields. This paper reports on these various aspects of crop management at the conventional, integrated and organic farms investigated. Two groups of integrated farms were hereby distinguished; a group of pioneer farmers (Innovation project (IP)) and a later-started group (A2000 project). Winter wheat cultivation on conventionally managed farms was very similar to cultivation at the integrated farms run under the A2000 project. By comparison, the IP integrated farms used a greater range of seed mixtures, sowed later and made less, and less frequent, use of growth regulators and pesticides. At both conventional and integrated farms there is an ongoing intensification of fertilizer and pesticide use. Management at ‘integrated’ farms is consequently increasingly similar to that at conventionally managed holdings. The organic farms differ in virtually every aspect of their management, and their management regime shows little variation over time. In the discussion the representativeness of the farms studied and the differences between, and the changes within, the IP and A2000 integrated farms are considered. It is concluded that the IP integrated farms meet the government’s environmental targets with respect to pesticide use, but not with respect to pesticide dependence.
The introduction of new agricultural practices (no tillage cropping and soybean transgenic cultivars resistant to glyphosate) to Argentina, together with market factors, have resulted in an increase in the area cropped with soybean and generated a new environment in the Rolling Pampas agroecosystem. During the summers of 1995, 1998, 1999, 2001 and 2003, a total of 120 soybean fields were surveyed, to evaluate the changes in the weed communities of the central Rolling Pampas through the period during which the adoption of these new technologies was increasing exponentially. Floristic structure was analyzed in terms of species composition, and functional structure in terms of morphotypes and physiotypes. Data were summarized by calculating species constancy, and alpha, beta, gamma diversity and functional richness. Alpha (local) diversity and functional richness were linearly related with gamma (regional) diversity and after an initial increase from 1995 to 1998, decreased over time, this being associated with the adoption of the new technologies. Beta diversity was not related to soybean regional pool of weed species, thus it was probably related to the availability of refuges provided by the landscape's habitat. Tillage system and cultivars were the main agronomic variable affecting the occurrence of weeds.
Estimates of soil organic carbon (SOC) stocks and changes under different land use systems can help determine vulnerability to land degradation. Such information is important for countries in arid areas with high susceptibility to desertification. SOC stocks, and predicted changes between 2000 and 2030, were determined at the national scale for Jordan using The Global Environment Facility Soil Organic Carbon (GEFSOC) Modelling System. For the purpose of this study, Jordan was divided into three natural regions (The Jordan Valley, the Uplands and the Badia) and three developmental regions (North, Middle and South). Based on this division, Jordan was divided into five zones (based on the dominant land use): the Jordan Valley, the North Uplands, the Middle Uplands, the South Uplands and the Badia. This information was merged using GIS, along with a map of rainfall isohyets, to produce a map with 498 polygons. Each of these was given a unique ID, a land management unit identifier and was characterized in terms of its dominant soil type. Historical land use data, current land use and future land use change scenarios were also assembled, forming major inputs of the modelling system.The GEFSOC Modelling System was then run to produce C stocks in Jordan for the years 1990, 2000 and 2030. The results were compared with conventional methods of estimating carbon stocks, such as the mapping based SOTER method. The results of these comparisons showed that the model runs are acceptable, taking into consideration the limited availability of long-term experimental soil data that can be used to validate them. The main findings of this research show that between 2000 and 2030, SOC may increase in heavily used areas under irrigation and will likely decrease in grazed rangelands that cover most of Jordan giving an overall decrease in total SOC over time if the land is indeed used under the estimated forms of land use.
Livestock production systems in Africa are experiencing rapid changes in structure and function due to increased demands for livestock products from a more prosperous and ever-increasing human population. Some of these changes could lead to increased emissions of greenhouse gases. This paper explores the magnitudes of changes in production systems as a function of increased population densities and climate change. This paper also quantifies the methane emissions from African cattle, goats and sheep from 2000 to 2030. The study integrates methodologies from different disciplines to derive spatially explicit distributions of methane emissions from domestic ruminants and their changes as livestock production systems evolve. A livestock systems classification framework was used to differentiate pastoral and crop–livestock systems using agro-ecological thresholds based on temperature and length of growing period (hyper-arid, arid, humid and temperate regions), the extent of irrigation and human population densities. Livestock numbers (tropical livestock units, TLU) were estimated from FAO data for each country and production system defined. Projections of livestock populations were derived from analysis of demand shifts in livestock products, and livestock systems changes estimated on the basis of potential climate change and population density change to 2030. For the estimation of diets for ruminants, Africa was split into regions (East, West, Southern, Central and North Africa, and The Horn of Africa) and diets for both the rainy and the dry seasons were estimated from literature reviews for each livestock species in each production system in each region. Feed intake, livestock production and the computation of methane emissions were obtained using a previously validated and widely used mechanistic model of digestion and metabolism in ruminants. Results suggest that (1) Africa produced around 7.8 million tonnes of methane/year in 2000. This figure is likely to increase to 11.1 million tonnes/year by 2030. (2) Methane emissions per tropical livestock unit (TLU, 250 kg bodyweight) can vary from 21 to 40 kg/(TLU year), depending on the production system and the region. (3) The highest emissions per animal come, and will continue to come, from ruminants in mixed crop–livestock systems. (4) The regions producing the highest concentrations of methane, now and in the future, are in general terms, The Horn of Africa, West and East Africa. (5) The average emission factors obtained in this study (31.1 kg/(methane (TLU year))) are in close agreement with the emission factors used by the International Panel on Climate Change (IPCC) for African ruminants (32 kg methane per animal per year). (6) The methodology employed in this study permits the disaggregation of methane emissions by country and production system, thus allows us to quantify changes in emissions as climate changes and production systems evolve. The results of the study are compared with those obtained in other studies around the world and its implications are discussed in relation to how systems are likely to evolve in Africa.
The value of environmental indicators largely depends upon the spatial and temporal scale that they represent. Environmental indicators are dependent upon data availability and also upon the scale for which statements are required. As these may not match, changes in scales may be necessary. In this paper a geostatistical approach to analyse quantitative environmental indicators has been used. Scales, defined in terms of resolution and procedures, are presented to translate data from one scale to another: upscaling to change from high resolution data towards a low resolution, and downscaling for the inverse process. The study is illustrated with three environmental indicators. The first concerns heavy metals in the environment, where the zinc content is used as the indicator. Initially, data were present at a 1 km2 resolution, and were downscaled to 1 m2 resolution. High resolution data collected later showed a reasonable correspondence with the downscaled data. Available covariates were also used. The second example is from the Rothamsted’s long-term experiments. Changes in scale are illustrated by simulating reduced data sets from the full dataset on grass cuts. A simple regression model related the yield from the second cut to that of the first cut in the cropping season. Reducing data availability (upscaling) resulted in poor estimates of the regression coefficients. The final example is on nitrate surpluses on Danish farms. Data at the field level are upscaled to the farm level, and the dispersion variance indicates differences between different farms. Geostatistical methods were useful to define, change and determine the most appropriate scales for environmental variables in space and in time.
Slash-and-burn agroecosystems are important to rural poor and indigenous peoples in the developing world. Ecologically sound slash-and-burn agriculture is sustainable because it does not depend upon outside inputs based on fossil energy for fertilizers, pesticides and irrigation. One means of demonstrating the soundness of slash-and-burn agroecosystems is to prove empirically the ecological compatibility of this system of crop production. This paper examines the ecological sustainability of slash-and-burn agriculture based on the productivity of soil resources.
Balance application of inorganic fertilizers and organic amendments greatly influence the accumulation of organic matter in soil and also the soil microbial activities. An investigation was carried out to study the changes in soil organic matter and biological properties as affected by long-term application of manure and fertilizers in maize (Zea mays)–wheat (Triticum aestivum)–cowpea (Vigna unguiculata) cropping system in a Cambisol in semi-arid region of India. The crop yield, soil organic C and total N and mineralizable C and N increased with the application of inorganic fertilizers. However, there was greater increase of these parameters when manure was applied along with inorganic fertilizers. Soil microbial biomass C was increased from 122 mg kg−1 in unfertilized treatments to 331 mg kg−1 in soil amended with 100% NPK+manure. The dehydrogenase, urease and alkaline phosphatase activities closely followed the soil organic carbon content and increased significantly with the addition of balanced nutrients and manure. The results indicated that soil organic matter content and soil microbial activities, vital for the nutrient turnover and long-term productivity of the soil, are enhanced by balanced application of nutrients and manure.
Recycling wastes in agriculture is an essential disposal method, and according to waste characteristics can produce supplementary organic-matter resources (sewage sludge, compost) for crop production, or valuable soil amendments (coal fly-ash). However, since heavy-metal content in waste materials is often higher than in the soil, application rates have to be carefully controlled, to obviate the possible accumulation of toxic metals in agricultural soils. The risk of the possible pollution of crops by heavy metals makes it necessary to use guidelines for waste utilization. Generally, guidelines and legislation refer to the total amounts of heavy metals in wastes and in soil. The total amount however, is of very low environmental importance and much international experimentation concerning these elements is actually engaged in determining the real availability of heavy metals to plants in relation to the chemical forms of heavy metals in the soil. This paper emphasizes the extractability of metals in relation to soil chemistry, and plant uptake bioassay as an important diagnostic tool for metal bioavailability.
Balanced application of inorganic fertilizer and organic amendments greatly influence the accumulation of organic matter in soil and also influence the soil physical environment. An investigation was carried out to study the long-term impact of fertilizer and manure application in a soybean–wheat–maize (fodder) crop rotation on soil organic carbon status and physical properties of a vertisol (Typic Haplustert or Pellic Vertisols) in sub-humid sub-tropical India. Five treatments namely, control (no fertilizer and manure), 100% of the optimum rate for nitrogen (100% N), 50% of the optimum rate for nitrogen, phosphorus and potassium (50% NPK), 100% of the optimum rate for NPK (100% NPK) and 100% NPK + farmyard manure at 15 Mg ha−1 (100% NPK + FYM) from a long-term fertilizer experiment continuing at Jabalpur, India, were chosen for this study. Soil samples were collected from the topsoil horizon (0–15 cm) of all the four replications of the selected five treatments in April 2000 after 28 crop cycles and analyzed for physical and chemical properties. The results showed that the soil organic carbon (SOC) content in 100% NPK and 100% NPK + FYM treatments increased, respectively, by 22.5 and 56.3% over the initial level (1.14 kg m−2). The electrical conductivity, SOC content, aggregation, water retention, microporosity and available water capacity of the soil were increased while the bulk density was reduced significantly with the 100% NPK + FYM treatment over all other treatments. However, the use of imbalanced (100% N) and suboptimal rate of inorganic fertilizer (50% NPK) as compared to the unfertilized control showed no significant effect on the physical properties of the soil. The study indicates that application of balanced rate of fertilizers in combination with organic manure could sequester soil organic carbon in the surface layer, improve the soil physical environment and sustain higher crop productivity under this intensive cropping system.
In an EU concerted action a checklist with criteria for the development of sustainable rural landscape was created. The idea of the concerted action was to bring together experts from various disciplines involved in management of the countryside. They represented disciplines from β, γ and α oriented sciences, ranging form environmentalists over sociologists to cultural geographers. They were all asked to list their (discipline’s) criteria and parameters for a sustainable management of the landscape. From all these criteria and parameters a checklist has been established. This checklist is presented in this paper, accompanied by an explanation of its basic concept that draws upon Maslow, its context, its methodology and its use. Finally summaries are presented of the ways the checklist, in various stages of its development, has been used in several European country countrysides. It can be concluded that the checklist is a useful tool for valuing the contribution of farms viz. farming systems to the regional development and the sustainability of the landscape. It was found that organic farms included in the sample of our research often performed rather well in that perspective as compared to the non-organic farms in that region.