Sustainable Agricultural Production Systems Research Articles

Monitoring changes in riverine forests of Sindh-Pakistan using remote sensing and GIS techniques

Depletion in the forest area threatens the sustainability of agricultural production systems and en-dangers the economy of the country. Every year extensive areas of arable agricultural and forestlands are degraded and turned into wastelands over time, due to natural causes or human interventions. Depletion in forest cover, therefore, has an important impact on socio-economic development and ecological balance. High population growth rate in Pakistan is one of the main causes for rapid deterioration of the physical environment and natural resource base. In view of this, it was felt necessary to carryout landuse studies focusing on mapping the past and present conditions and the extent of forests and rangelands using satellite remote sensing (SRS) and Geographic Information System (GIS) technologies. The SRS and GIS technologies provide a possible means of monitoring and mapping the changes occurring in natural resources and the environment on a continuous basis. The riverine forests of Sindh mostly growing along the river Indus in the flood plains are spread over an area of 241,000 ha but are disappearing very rapidly. Construction of dams/barrages on the upper reaches of the river Indus for hydroelectric power and irrigation works have significantly reduced the discharge of fresh water into the lower Indus basin and as a result 100,000 acres of forests have disappeared. Furthermore, heavy floods that occurred in 1978, 1988, 1992 and 1997, altered the course of the River Indus in many places, especially in the lower reaches, this has also damaged the riverine forests of Sindh. An integrated approach involving analysis of SRS data from 1977 to 1998 and GIS technique have been used to evaluate the geographic extent and distribution of the riverine forests of Sindh and to monitor temporal changes in the forest cover between 1977 and 1990; 1990 and 1998; and 1977 and 1998. The integrated landuse forest cover maps have shown not only the temporal changes that occur in the riverine forest but also in the river Indus course between 22 years period.

Environmental impact of panela food-processing industry: sustainable agriculture and local agri-food production systems

Environmental valuation multi-stakeholder processes, as advocated by ecological economics, often have a strong local character. Critical Natural Capital cannot be defined without referring to a given geographical scale, very often local in terms of the definition of the environmental resource at stake and the relevant stakeholders involved in the evaluation and decision process. In this setting, environmental valuation processes cannot be disentangled from socio-economic dimensions of local social development, as shown by various examples and especially by the one of local agri-food systems of panela production in specific areas of Colombia. While there exist cost-effective technological innovations that can reduce the ecological impact of the panela commodity chain, these innovations can be fully implemented only if the producers can rely on anticipations of the development of a market for quality biological panela that can be traced back to specific areas of production.

Bermudagrass Management in the Southern Piedmont, USA

An understanding of the long-term cycling of trace elements in soil with broiler litter fertilization under various forage utilization strategies is needed to develop sustainable agricultural production systems. We evaluated differences in Cu, Mn, Zn, and six other trace elements in response to 5 yr of bermudagrass [Cynodon dactylon (L.) Pers.] management varying in fertilization and harvest strategies on a Typic Kanhapludult in Georgia. Chicken (Gallus gallus) broiler litter was a significant source of trace elements that led to 3.4 ± 0.5 times higher Cu, 2.0 ± 0.3 times higher Mn, and 2.1 ± 0.2 times higher Zn in the surface 3 cm of soil than when forage was fertilized inorganically. There were variable effects of broiler litter fertilization on other trace elements, depending upon element, depth of sampling, and forage utilization strategy. Concentrations of all trace elements in soil were below levels considered toxic to plants. Soil at a depth of 0 to 3 cm under grazed paddocks had 33 ± 5% greater Cd, 18 ± 1% greater Cr, 53 ± 24% greater Cu, and 24 ± 7% greater Zn compared with unharvested and hayed management. Trace elements in soil were unaffected whether forage was unharvested or removed as hay. These results suggest that broiler litter is a significant source of several trace elements and that ruminant processing of forage and subsequent deposition of excreta on the paddock allow these trace elements to accumulate more at the soil surface where they might interact with the high concentration of organic matter.

Productivity and soil nutrient relations of bedwork watermeadows in southern England

Irrigation (or ‘floating’) of watermeadows in Europe was economically important before the 20th century because it enhanced grazing sward productivity in the spring. Today, few operational systems remain, but interest in floating as a technique is returning as concern grows over floodplain management, the fate of nutrients and the sustainability of agricultural production systems. Investigations into grass productivity, phosphorus and nitrogen relations were undertaken at a surviving watermeadow system, the Britford Site of Special Scientific Interest, Salisbury, England (1995–2001) and at an experimental site at Norwich, England (1998–2001). Irrigation significantly increased late-winter and early-spring grass productivity at Britford in the order of 60–80% over 5 weeks compared with un-irrigated controls. Phosphorus travelled across the system; some included with the clay fraction in suspended sediment, but available phosphorus in the topsoil reduced across the meadows by between one-half and one-third. Nitrate in irrigation water was utilised, but the meadow system did not reduce concentrations of dissolved nitrate. Increased nitrate concentration in soil-water is attributed to mineralisation after drainage. Annual nitrogen cycle process modelling suggests the present levels of production and soil organic matter accumulation are attributable to environmental eutrophication. A conceptual model is presented for enhanced spring growth following floating and it is concluded that, while temperature is the trigger that enhances productivity early in the season, this is achieved by enhancing the mineralisation of soil organic matter and release of available nitrogen. There was no evidence that watermeadows act as a sink for nitrogen mobile in surface waters but there was significant uptake of topsoil available phosphorus.

Evaluation of sustainability of organic, integrated and conventional farming systems: a farm and field-scale analysis

Agricultural researchers widely recognise the importance of sustainable agricultural production systems and the need to develop appropriate methods to measure sustainability. The principal purpose of this paper is to evaluate the financial and environmental aspects of sustainability of organic, integrated and conventional farming systems (OFS, IFS and CFS, respectively) at farm level and on more detailed spatial scales. This was achieved by applying an integrated economic-environmental accounting framework to three case study farms in Tuscany (Italy) covering different farming systems (FSs) and different spatial scales. The environmental performances of the FSs were measured through the application of an environmental accounting information system (EAIS) at field, site and farm level. The EAIS indicators were then integrated with: (1) a set of financial indicators to evaluate the economic and environmental trade-offs between different FSs and (2) with information on the regional and site-specific soil and climate conditions to study the impact of different pedo-climates on the environmental performances of the FSs. The gross margins of steady-state OFSs were found to be higher than the corresponding CFS gross margins. The OFSs perform better than IFSs and CFSs with respect to nitrogen losses, pesticide risk, herbaceous plant biodiversity and most of the other environmental indicators. However, on hilly soils, erosion was found to be higher in OFSs than in CFSs. The pesticide and the nitrogen indicators in this study showed a similar environmental impact caused by integrated and conventional farming practices. Regional pedo-climatic factors were found to have a considerable impact on nutrient losses, soil erosion, pesticide risk and herbaceous plant biodiversity, site-specific factors on nutrient losses and soil erosion. Results at field level suggest that herbaceous plant biodiversity and crop production are not always conflicting variables. Results of the case study farms are discussed and compared with environmental sustainability thresholds reported from EU Directives on nitrate and pesticides in groundwater and the literature.

Abundance and diversity of Carabidae (Coleoptera) in different farming systems

Commercial farms were examined in western Canada to assess the impact of two cropping systems (annual-grain and diversified grain-forage) and two input systems (high level and organic) on carabid beetles. Pitfall traps were used to sample beetles over 3 years (1994–1996). Results showed that five species of Carabidae dominated the 51 species captured ( Bembidion quadrimaculatum (LeConte), Bembidion obscurellum (Motschulsky), Agonum placidum (Say), Amara littoralis (Mannerheim), Bembidion nitidum (Kirby)). The annual-grain system was found to support greater species diversity than the diversified grain-forage system but there was no significant difference in the mean abundance. There were no significant differences between species diversity or mean abundance in high input versus organic systems. An inventory of carabids associated with specific agricultural production systems in Saskatchewan was developed, based on data collection and evaluation by crop, pest, economic and soil scientists, which are intended to monitor long-term sustainable agricultural production systems.

Agriculture Intensification and Ecologically Sustainable Land Use in Niger: A Case Study of Evolution of Intensive Systems with Supplementary Irrigation

ABSTRACT In Niger, a breakdown of the bush-fallow system, low crop yields and reduced availability of communal land have resulted from increasing population pressure. Agricultural intensification is critical to the future development of the region. Intensification of agricultural production in Niger must include adoption of sustainable yield increasing technologies, fertilizer use, supplementary irrigation and/or water conservation, high yielding cultivars and improved crop management practices. On-farm constraints analysis of crop productivity and technologies assessment was carried out in two irrigated perimeters: the Konni surface irrigation and the Djirataoua deep well system where supplemental irrigation is provided to rainy season crops in the event of long dry spells, and full irrigation is supplied to dry season crops. Konni is located in southern Niger, approximately 13°48'0′N, 5°15'0′E at approximately 257 m altitude; Djirataoua is located further east, approximately 13°20'0′N, 7°7'60′E at approximately 368 m altitude, near Maradi, which is located at approximately 13°28°60′N, 7°5′60E, approximately 376 m altitude. In both the Konni and Djirataoua irrigation systems, use of supplementary irrigation has enhanced cropping intensity and crop productivity per unit area (yield) while generating greater employment opportunity. Analysis of long-term crop productivity trends during 1980–1997 revealed that sustainability of gained productivity is possible through agricultural intensification over years without any sign of productivity decline. These results show that the use of agriculture intensification technologies plays a crucial role in sustainable, increased crop production in the Sahel. The results of our diagnostic survey in these two perimeters showed that the major constraints to increased productivity are low fertilizer use, poor nutrient use efficiency, the lack of well adapted, high yielding varieties or hybrids, poor crop establishment and plant protection in farmers fields, and inappropriate input and output pricing. On-farm evaluation of the improved technologies, namely improved varieties or hybrids and optimal fertilizer use with optimal supplementary irrigation, resulted in a 35% increase in grain yields at the farm level. The lesson learned from this study is that developing sustainable agricultural production systems in Niger with higher yields, or production per unit area, than present-day yields depends upon supplementary irrigation if or where potential exists, and upon promotion of fertilizer use, high yielding cultivars and other innovative production technologies. This strategy will help reduce frequency and intensity of food shortages and will ultimately help reduce the incidence of poverty and starvation in Niger.

Organic Farming in the Nordic Countries – Animal Health and Production

Organic farming (or ecological agriculture) is of growing importance in the agricultural sector worldwide. In the Nordic countries, 1-10% of the arable land was in organic production in 1999. Organic farming can be seen as an approach to agriculture where the aim is to create integrated, humane, environmentally and economically sustainable agricultural production systems. Principles like nutrient recycling, prevention rather than treatment and the precautionary principle are included in aims and standards. Animal welfare is another hallmark of organic livestock production but despite this, several studies have indicated severe health problems e.g. in organic poultry production in Denmark. Also the quality of animal food products in relation to human health, particularly the risk of zoonotic infections, has been debated. For these reasons there is a need for improvement of production methods and animal health status. Vets play an important role in this development through work in clinical practice and in research. On-farm consultancy should be tailored to the individual farmers needs, and the practitioner should be willing to take up new ideas and when needed, to enter a critical dialogue in relation to animal welfare. Better base line data on animal health and food safety in organic food systems are needed.

Rice (Oryza sativa)-based farming systems for livelihood improvement of Indian farmers

Farming system research is a multi-disciplinary holistic approach to solve the problems of small and marginal farms. Small and marginal farmers are the core of the Indian rural economy constituting 80% of the total farming community but possessing only 36% of the total operational land. The declining trend of per caput land availability poses a serious challenge to the sustainability and profitability of farming. Under such conditions, it is appropriate to integrate land-based enterprises, viz. dairy, fishery, poultry, duckery, apiary, field and horticultural crops within the farm, with the objective of generating adequate income and employment for these small and marginal farmers and thereby improved livelihoods. The production system adopted during Green Revolution has been explorative and the natural resources like soil and water were subjected to immense pressure beyond carrying capacity. As a result sustainability of agricultural production system and the farming system is in crises. This suggests the urgent need of integrated farming system development where the various components of the farming system may be in- tegrated to improve productivity and profitability as well as resource conservation along with maintenance of the environment. Rice ( Oryza sativa L.) occupies a position of overwhelming importance in Asian agriculture and it constitutes the bulk of the Asian diet. For many people in the poor countries, rice is the main source of energy, and it plays an important role in providing livelihood to the Asian population. It is largely grown in Asia (90% area) under diverse conditions of soil, climate, hydrology and topography. Rice farming is the single most important source of employment and income for the majority of rural people in these regions. Among the various farming system options in rice ecologies, rice fish farming has great potential particularly in eastern India in view of the resources, food habits and other socio-economic conditions. Ricefish diversified farming system with the integra- tion of compatible components, such as improved varieties of rice, fish, prawn, pulses, oilseeds, horticultural crops, agroforestry, mushroom, poultry, duckery, goatery, floriculture, apiculture etc. can increase the farm pro- ductivity, besides farm employment over traditional rice farming. There exist chain of interactions and flow of re- sources among the different enterprises in a integrated farming system. To make farming profitable and improve resource use efficiency at the farm level, the synergy among interacting components of farming system needs to be exploited. In this paper focus is on different aspect of rice-based farming system involving methodology, deter- minants, and forms of rice-based farming systems and their impact on livelihood of farming communities.

Potential for improving pea production by co-inoculation with fluorescent Pseudomonas and Rhizobium

Seed bacterization with five plant growth promoting fluorescent Pseudomonas strains isolated from Indian and Swedish soils and three Rhizobium leguminosarumbiovar viceae strains isolated from Swedish soils were shown to promote plant growth in Pisum sativum L. cv. Capella. Co-inoculation of the fluorescent pseudomonads and Rhizobium improved plant growth in terms of shoot height, root length and dry weight. Both the fluorescent pseudomonads and Rhizobium were shown to exhibit a wide range of antifungal activity against pathogens specific to pea. Seed bacterization with plant growth promoting strains alone and together with a rhizobial isolate, R 361-27 reduced the number of infected peas grown in Fusarium oxysporum infested soils. We found that the introduced organisms were able to colonize the roots, which was confirmed using immunofluorescence staining and drug resistant mutant strains. In a synthetic culture medium, all the plant growth promoting fluorescent pseudomonads strains produced siderophores, which shown to express antifungal and antibacterial activity. Our results suggest the potential use of these bacteria to induce plant growth and disease suppression in sustainable agriculture production systems.

Agroecological zones and the assessment of crop production potential

The rapidly growing world population puts considerable pressure on the scarce natural resources, and there is an urgent need to develop more efficient and sustainable agricultural production systems to feed the growing population. This should be based on an initial assessment of the physical and biological potential of natural resources, which can vary greatly. The agroecological zonation (AEZ) approach presents a useful preliminary evaluation of this potential, and ensures that representation is maintained at an appropriate biogeographic scale for regional sustainable development planning. The principal AEZs of the world, as described by the Technical Advisory Committee of the Consultative Group on International Agricultural Research, are presented along with their extent and characteristics. Net primary productivity of terrestrial vegetation can be assessed from weather data, and it varies from 1 t dry matter ha −1 yr −1 in high latitude zones and dry regions to 29 t ha −1 yr −1 in tropical wet regions, depending on the climatic conditions. To assess the crop production potential, length of the growing period zones, a concept introduced by the UN Food and Agriculture Organization, is very useful as it describes an area within which rainfall and temperature conditions are suitable for crop growth for a given number of days in the year. These data, combined with the information on soils and known requirements of different food crops, can be used to assess the potential crop productivity. Some perspectives on AEZs and crop production potential are presented by describing the manner in which production potential can be integrated with present constraints. Efforts to intensify production should place emphasis on methods appropriate to the socio-economic conditions in a given AEZ, and on promotion of conservation-effective and sustainable production systems to meet the food, fodder and fuel needs for the future.

Biotechnology applied to grain legumes

Recent advances in grain legume biotechnology are reviewed. Emphasis is given on field testing and commercialization of transgenic grain legumes. The absence of variety-independent gene transfer methods for major agronomic species has, until now, limited the usefulness of recombinant DNA techniques to crop improvement programs. Direct DNA transfer techniques into organized and easily regenerable tissue provided the breakthrough to achieve effective and practical gene transfer into important leguminous species. In principle, we are now in the position to introduce any foreign gene into almost all major legumes, in some cases in a variety-independent fashion. This, however, can only be achieved routinely in few laboratories, all located in industrialized countries. A number of the more important of the leguminous crops, particularly those utilized for human consumption are important components of sustainable agricultural production systems in the developing world. We must bridge the gap between industrialized and developing countries before legume biotechnolgy can be utilized effectively for crop improvement, particularly in the developing world. Technology transfer becomes an important issue and links amongst corporate research organizations, academic institutions and international organizations need to be strengthened to avoid duplication of effort and to maximize efficient utilization of limited resources. In this chapter, advantages of the various gene delivery methods that were shown to be useful for specific crops, as well as limitations and problems associated with each crop and gene transfer method will be discussed. In addition, we will focus on specific biotechnology goals targeted for particular crops. Important oilseed and feed species as well as minor but equally important species for sustaining growing populations in developing countries are discussed.

The effect of irrigation on the carbonate status of Chernozems of Central Precaucasus (Russia)

Non-irrigated and irrigated Ordinary Chernozems of Stavropol Upland, Central Precaucasus (Russia), were examined. A number of morphological and instrumental methods was used for detailed investigation of the carbonates in the soils. This approach allowed us to reveal the essential change of the carbonate status of the irrigated Chernozems as a result of changing the soil moisture regime and the predominance of leaching processes under 30 years irrigation by fresh water. The changes included distinct enhancement of spatial variability and instability of carbonate-illuvial horizon deposition, the highest data scatter on carbonate content within this horizon, the signs of increased mobility of carbonate material and the change of the mechanism of the carbonate accumulations. Carbonates moving with soil solutions and mobile migrational forms of carbonate accumulations as well as segregating forms and lithogenic concretions were transformed under the irrigation. Irrigation for 30 years resulted in unfavorable reclamative changes of the Ordinary Chernozems carbonate status: decalcification of the upper part of the solum, disappearance of the mobile carbonate accumulations from the upper horizons, the initial point of the compact carbonate-hardened horizon in the low part of profile and the increase of the calcium and magnesium content in the soil solution. The problem studied is complicated because of the inherent variability of carbonate parameters and the multitude of factors having an influence on carbonate status. Much more work is needed because of the importance of the topic for sustainability of agricultural production systems, for prediction and overcoming of unfavorable consequences of irrigation, for the up-to-date problem of the greenhouse effect and the response of carbonate reserves to climate changes.

Concepts in production ecology for analysis and quantification of agricultural input-output combinations

Definitions and concepts of production ecology are presented as a basis for development of alternative production technologies characterized by their input-output combinations. With these concepts the relative importance of several growth factors and inputs is investigated to explain actual yield levels and resource-use efficiencies. Differences between potential and actual levels are analyzed to open ways for improved production technologies. The basis of the analysis is knowledge of basic physical, chemical, physiological and ecological processes at soil, field and crop level. New production technologies and their input-output combinations can be used in studies aimed at the exploration of options for sustainable agricultural production systems and land use. The concepts allow a systematic analysis and quantification of input-output combinations and clearly discriminate between bio-physical possibilities and socio-economic constraints and objectives. They help in defining objectives and means for agricultural production and land use, and may be valuable as aids to communication between various disciplines involved in studying the possibility and feasibility of future production technologies and land use options. The concepts production level, physical environment, target-oriented approach, production technique, production activity, and production orientation are applied to identify new technologies and production systems at various levels of scale, each requiring different types of information. In this paper some examples of applications are given at field, farm and at regional level.

Combating micronutrient deficiencies through vegetables—a neglected food frontier in Asia

The widespread prevalence of micronutrient deficiency is a major cause of poor human health in many developing countries of Asia. Integrating micronutrient-rich foods such as vegetables, fruits and livestock products into diets is the most practical and sustainable way to alleviate micronutrient deficiency. Vegetables are efficient sources of several important micronutrients, both with respect to unit cost of production and per unit of land area. However, vegetable consumption in most Asian countries is far below the level required to meet the micronutrient requirements. This is further aggravated by seasonal and annual fluctuations in vegetable production and consumption. The per capita consumption of vegetables has stagnated at low levels in most Asian countries, and real vegetable prices are on the increase. Policies to ameliorate micronutrient deficiency include reduction in the relative prices of vegetables, increase in income, enhancement of micronutrient contents in vegetables, generating awareness among consumers about the role of vegetables in human health, improvement in vegetable cooking and processing methods and improvement in the gestropolitics of micronutrient distribution. Enhancing vegetable supplies through low-cost production and marketing technology, and advance vegetable cooking and processing methods coupled with educational programs to promote a balanced diet is considered the most efficient strategy to solve the problem of mineral and vitamic deficiency, along with an increased food and income security, new jobs, food diversity, and enhanced sustainability of agricultural production systems that results from the diversification of these systems. Such efforts should not be targeted at a single vegetable or single micronutrient, but rather to enhance overall vegetable supplies, especially during the lean supply period, as well as to increase their diversity usually demanded by consumers when they start consuming more vegetables.

Leaf litter ash alkalinity and neutralisation of soil acidity

Soil acidification is a major factor limiting the sustainability of agricultural production systems throughout the world. Liming may not always be economically possible and therefore alternative methods or complementary methods of amelioration are required. Leaf litter collected from several tree species was examined for ash alkalinity (as an estimate of organic anion content) and ability to ameliorate an acid soil. Ash alkalinity measured by titration of the ash and excess cation values obtained by calculation as the difference between cation and anion content were correlated. Values obtained by the latter method ranged from 247 cmolc kg-1 for Melia azedarach (white cedar) to 36 cmolc kg-1 for Eucalyptus globoidea (white stringybark). There was a significant linear correlation between ash alkalinity and the Ca concentration in the litter. When added to an acid soil (pH 4.04 measured in 0.01 M calcium chloride) and incubated for 8 weeks, leaf litter raised the pH. Species differed markedly with Melia azedarach having the greatest effect. The increase in pH was proportional to the quantity of ash alkalinity (organic anions) added, expressed as calcium carbonate equivalents. Aluminium levels on the exchange complex were lowered by treatment with leaf litter through direct precipitation of a solid phase and again Melia azedarach litter was most effective. There was also indirect evidence of organo-Al complexes affecting the concentration of monomeric Al in soil treated with litter from Liquidambar styraciflua (liquidambar), Quercus robur (English oak) and Pinus radiata (radiata pine).

Integrated crop management: An approach to sustainable agricultural development

Abstract In developing countries, agriculture is being intensified to produce more food and agricultural products. In most agricultural development strategies, the order of priorities is on: (i) increasing yields, (ii) crop protection, and (iii) human health, environmental and social aspects. This sequential rather than integrated approach contributes to many problems related to sustainability in agriculture. Examples of increased problems with soil erosion, secondary salinization and waterlogging, soil nutrient depletion, increased pest problems, public health hazards and environmental pollution illustrate this phenomenon. To improve the present situation, agricultural development strategies should be based on an integration of factors determining the agricultural production potential of a particular zone: the biophysical environment, the land reclamation level, and external input use. Integrated Crop Management and systems analyses can help to put these factors in the best perspective, and to set the priorities for agricultural research and development accordingly. Techniques aimed at sustainability are listed, and their use is discussed in areas with different production potentials. To assess the impact of cropping techniques on the sustainability of agricultural production systems, suggestions are made for the monitoring of selected physical, chemical and biotic characteristics of agro‐ecosystems.

A framework for evaluating the sustainability of agricultural production systems

AbstractSustainable agriculture has gained acceptance as a conceptual approach for shaping farming systems of the future. All definitions of sustainable agriculture include food productivity, food safety, resource protection, quality of life and environmental quality. However, the sustainability of a wide range of farming systems has been judged only subjectively. Currently there are no scientific criteria to evaluate the sustainability of a specific farming system. We propose a framework for evaluating the relative sustainability of a farming system using nine attributes: profitability, productivity, soil quality, water quality, air quality, energy efficiency, fish and wildlife habitat, quality of life, and social acceptance. Each attribute is scored and then weighted in a way that is subjective and dependent on the judgment of the evaluating team, but that must be expressed numerically. The scoring must be based on quantifiable constraints within each attribute. Constraints can be quantified by direct measurement, which is already true for those related to profitability, productivity, water quality and energy efficiency. Constraints that are not readily measurable will need other evaluation techniques, including expert opinion and computer simulation models.

Spring Wheat Yield Trends as Influenced by Fertilizer and Legumes

The benefits and environmental impacts of using fertilizers rather than legumes to promote more sustainable agricultural production systems are in question. The objective of this study was to demonstrate the long-term consequences of withholding fertilizer N and P on wheat (Triticum aestivum L.) yields, and to determine if inclusion of legume-green manures (GM), or hay crops in rotations can maintain wheat yields. A 34-yr crop rotation experiment being conducted at Indian Head, Saskatchewan, on a Udic Haploboroll with heavy clay texture, was used to assess the influence of fertilizer (N and P), sweetclover (Melilotus officinalis L.) GM, and alfalfa-bromegrass (Medicago sativa L. - Bromus inermis Leyss.) hay on yield trends of hard red spring wheat grown on wheat stubble in rotations of varying cropping intensity [...]

Nitrogen Cycling in Pasture and Range

Direct recycling of nutrients by grazing animals is often suggested as a means to achieve a sustainable agricultural production system. The mere presence, however, of large herbivores, their management, and uncontrollable site-specific environmental conditions can cause significant nutrient losses. Nitrogen is of particular interest because it is usually the most limiting nutrient to production; it represents a major variable input cost; it has a variety of pathways for input and outflow; and it can have important negative environmental impacts. Large herbivores shorten the N cycle, increase the rate of N cycling, and cause significant redistribution of N. Input of N through symbiotic N2 fixation is greatest in tropical and temperate pastures, whereas wet and dry deposition provide much of the usable N under semiarid conditions. Pathways of N loss also vary with climate, with gaseous losses predominating in dry conditions and NO−3 leaching predominating under high rainfall. Spatial and temporal variability in pasture and rangeland N cycles has limited our ability to predict the effects of management decisions on N losses. Development of new experimental methodologies promises substantial advances in our understanding of nutrient cycling processes, from the scale of the microsite to that of the ecosystem.