Chemistry, availability and mobility of molybdenum in Colorado soils, The

December 1975.Covers not scanned.Includes bibliographical references.Print version deaccessioned 2022.The purpose of this study was to investigate the impact of molybdenum contamination in irrigation water on soils and pastures in Colorado. The chemistry, availability and mobility of Mo was studied in the laboratory, greenhouse, and field. These results were incorporated into a dynamic computer simulation model that predicts Mo accumulation in forages. Solubility diagrams were constructed from thermodynamic data for naturally occurring molybdenum minerals. The solubility of molybdenum in selected Colorado soils was compared with that predicted by the solubility diagrams. Molybdenum minerals were found to control the solubility of Mo in only one of the thirteen soils studied. Addition of wulfenite (PbMoO4), the most stable Mo mineral, raised the Mo solubility to conform to the solubility isotherm of wulfenite in soils. In the remaining twelve soils the solubility of Mo was controlled by specific adsorption processes, and changed with the degree of Mo saturation and pH. The Freundlich adsorption isotherm was extended with a pH term to describe the solubility relationship of Mo in soils. The availability of Mo in soils was studied in both greenhouse and field. Additions of Na2MoO4 to soils increased the uptake of Mo by alfalfa, clover, and bluegrass; the uptake increased with alkalinity. Water-extractable or (NH4)2CO3-extractable soil Mo accurately predicted the concentration of Mo in alfalfa grown on neutral and alkaline soils (r= .97 in the greenhouse, and r= .85 in the field). The information obtained in the laboratory and greenhouse studies was used to develop a computer model to simulate the impact of high-Mo irrigation water on soils and forages. The model used simulated daily growth of alfalfa under climatic conditions typical for Colorado. Changes in the Mo content of the rhizosphere were evaluated daily by considering inputs from irrigation water and losses from leaching and plant uptake. The impact of Mo contamination on forage was shown to depend on the quality and amount of irrigation water applied to the field, as well as on the type and leachability of the soil. Toxic levels of Mo were predicted for alfalfa grown on a clayey soil after 15 years of irrigation with 300 mm of water containing 100 ppb Mo. It was demonstrated that most soils irrigated with water containing more than 25 ppb Mo will eventually produce toxic forages

Trade-offs in multi-purpose land use under land degradation

CITATION: Vlek, P. L. G., et al. 2017. Trade-offs in multi-purpose land use under land degradation. Sustainability, 9(12):2196, doi:10.3390/su9122196.The original publication is available at http://www.mdpi.com/journal/sustainabilityAbstract: Land provides a host of ecosystem services, of which the provisioning services are often considered paramount. As the demand for agricultural products multiplies, other ecosystem services are being degraded or lost entirely. Finding a sustainable trade-off between food production and one or more of other ecosystem services, given the variety of stakeholders, is a matter of optimizing land use in a dynamic and complex socio-ecological system. Land degradation reduces our options to meet both food demands and environmental needs. In order to illustrate this trade-off dilemma, four representative services, carbon sinks, water storage, biodiversity, and space for urbanization, are discussed here based on a review of contemporary literature that cuts across the domain of ecosystem services that are provided by land. Agricultural research will have to expand its focus from the field to the landscape level and in the process examine the cost of production that internalizes environmental costs. In some situations, the public cost of agriculture in marginal environments outweighs the private gains, even with the best technologies in place. Land use and city planners will increasingly have to address the cost of occupying productive agricultural land or the conversion of natural habitats. Landscape designs and urban planning should aim for the preservation of agricultural land and the integrated management of land resources by closing water and nutrient cycles, and by restoring biodiversity.https://www.mdpi.com/2071-1050/9/12/2196Publisher's versio

Combined Effects of Legumes with Rock Phosphorus on Rice in West Africa

Rice (Oryza sativa L.) demand in West Africa is unmet because of insufficient production. Legume fixed N [biological N fixation (BNF)] may sustainably increase rice productivity in low-input systems. However, P deficiency limits BNF on the acid soils encountered in the region, despite the prevalence of phosphate rock (PR). Pot and field experiments were conducted in Côte d'Ivoire in 1996–1998 to study the impact of combined legume and PR on rice performance. Triple superphosphate and PR were applied at rates of 60 (pot) and at 90 (field) kg P ha−1 to rice and the legume Aeschynomene afraspera grown for 8 wk and then incorporated before rice transplanting. Legume fixed N was determined by 15N isotope dilution. Under field conditions, addition of PR doubled the biomass of A. afraspera Irrespective of P source, P application increased the amount of BNF-N (three- to eightfold) to 36 mg N plant−l in pots and to 84 kg N ha−1 in the field. Nitrogen derived from the air was correlated with legume P uptake (r = 0.97***, where *** = significant at the 0.001 level) and nodulation (r = 0.91**, where ** = significant at the 0.01 level). The synergy of PR and BNF on N and P cycling improved P nutrition and total biomass of subsequent lowland rice under pot conditions. Combining legume green manure (GM) with PR enhanced soil extractable Bray-1 P and may thus play an important role in improving the availability of PR. Under field conditions, due to asynchrony in GM nutrient release and demand, the impact of the combined GM–PR treatment on rice yield was minimal

Soil Erosion Prediction Using Morgan-Morgan-Finney Model in a GIS Environment in Northern Ethiopia Catchment

Even though scientific information on spatial distribution of hydrophysical parameters is critical for understanding erosion processes and designing suitable technologies, little is known in Geographical Information System (GIS) application in developing spatial hydrophysical data inputs and their application in Morgan-Morgan-Finney (MMF) erosion model. This study was aimed to derive spatial distribution of hydrophysical parameters and apply them in the Morgan-Morgan-Finney (MMF) model for estimating soil erosion in the Mai-Negus catchment, northern Ethiopia. Major data input for the model include climate, topography, land use, and soil data. This study demonstrated using MMF model that the rate of soil detachment varied from 170 t ha−1 y−1, whereas the soil transport capacity of overland flow (TC) ranged from 5 t ha−1 y−1 to >42 t ha−1 y−1. The average soil loss estimated by TC using MMF model at catchment level was 26 t ha−1 y−1. In most parts of the catchment (>80%), the model predicted soil loss rates higher than the maximum tolerable rate (18 t ha−1 y−1) estimated for Ethiopia. Hence, introducing appropriate interventions based on the erosion severity predicted by MMF model in the catchment is crucial for sustainable natural resources management

Nutrient and virtual water flows in traded agricultural commodities

Globalization and increasing population pressure on food demand and land and water resources have stimulated interest in nutrient and virtual water flows at the international level. West Asia/North Africa (WANA), Southeast Asia, and sub-Saharan Africa are net importers not only of nitrogen, phosphorus, and potassium (NPK) but also of virtual water in agricultural commodities. Nevertheless, the widely recognized declines in soil fertility and problems related to water shortage continue to increase, especially in sub-Saharan Africa. The nutrients imported are commonly concentrated in the cities, creating waste disposal problems rather than alleviating deficiencies in rural soils. And also the water shortage problems continue to contribute to intensified desertification processes, which again lead to increased urbanization and thus water shortage problems in cities. Countries with a net loss of NPK and virtual water in agricultural commodities are the major food exporting countries-the USA, Australia, and some Latin American countries. Understanding the manifold factors determining the nutrient and water flows is essential. Only then can solutions be found which ensure a sustainable use of nutrients and water resources. The chapter ends by stressing the need for factoring environmental costs into the debate on nutrient and water management, and advocates more transdisciplinary research on these important problems