Flue gas desulfurization by-products additions to acid soil: alfalfa productivity and environmental quality

Flue gas desulfurization (FGD) by-products are created when coal is burned and SO2 is removed from the flue gases. These FGD by-products are often alkaline and contain many plant nutrients. Land application of FGD by-products is encouraged but little information is available related to plant responses and environmental impacts concerning such use. Agricultural lime (ag-lime) and several new types of FGD by-products which contain either vermiculite or perlite were applied at 0, 0.5, 1.0, and 2.0 times the soil's lime requirement (LR) rate to an acidic soil (Wooster silt loam). The highest FGD by-products application rate was equivalent to 75.2 Mg ha(-1). Growth of alfalfa (Medicago sativa L.) was significantly increased compared to the untreated control in the second year after treatment with yields for the 1 x LR rate of FGD approximately 7-8 times greater compared to the untreated control and 30% greater than for the commercial ag-lime. Concentrations of Mo in alfalfa were significantly increased by FGD by-products application, compared to the untreated control, while compared to the ag-lime treatment, concentrations of B increased and Ba decreased. No soil contamination problems were observed, even at the 2xLR rate, indicating these materials can be safely applied to agricultural soils.     

Sensitivity of submersed freshwater macrophytes and endpoints in laboratory toxicity tests

The toxicological sensitivity and variability of a range of macrophyte endpoints were statistically tested with data from chronic, non-axenic, macrophyte toxicity tests. Five submersed freshwater macrophytes, four pesticides/biocides and 13 endpoints were included in the statistical analyses. Root endpoints, reflecting root growth, were most sensitive in the toxicity tests, while endpoints relating to biomass, growth and shoot length were less sensitive. The endpoints with the lowest coefficients of variation were not necessarily the endpoints, which were toxicologically most sensitive. Differences in sensitivity were in the range of 10-1000 for different macrophyte-specific endpoints. No macrophyte species was consistently the most sensitive. Criteria to select endpoints in macrophyte toxicity tests should include toxicological sensitivity, variance and ecological relevance. Hence, macrophyte toxicity tests should comprise an array of endpoints, including very sensitive endpoints like those relating to root growth.     

A Systemic Approach to Scoping of Factors Influencing More Sustainable Land Use in Herefordshire

Abstract

Defining and putting into practice sustainable land use is a complex, systemic problem. Systems models and techniques were used in a study of Herefordshire to clarify the situation and identify the potential for a more locally focused, learning-based approach to land use. Issues included: (i) uncertainty about the boundary of a ‘system of sustainable Herefordshire land use’; (ii) the complexity of economic flows in the county and the absence of some critical data; (iii) the importance of the Herefordshire landscape to tourism and the role of agriculture as a determinant of the state of that landscape; (iv) weakness of the institutional linkage between tourism and agriculture; (v) the current lack of inclusion of many relevant stakeholders in concerted action. Factors favouring a learning approach included a strong local identity, local food-related developments, and educational initiatives. Barriers to such an approach included questions of power and landholding, government policies, and attitudes and skills within organizations. These findings are considered in relation to the wider debate over approaches to sustainability.     

A review: long-term effects of agricultural systems on soil biochemical and microbial parameters

This paper provides a review of recent developments on assessing the effect of agricultural systems on long-term productivity of soils. Cultivation of soils, besides affecting soil chemistry and structure, reduces biological activity due to the reduction of macroaggregates which provides an important microhabitat for microbial activity. Indirect evidence suggests that soil amendments such as animal and green manures, and plant diversity (crop rotations) may be more important in maintaining soil microbial activity/diversity than conservation tillage in monocultural systems. There is increasing evidence that crop rotation promotes crop productivity by suppressing deleterious microorganisms that flourish under monoculture. Additions of inorganic fertilizers can increase soil biological activity because of an increased plant biomass production which upon incorporation stimulates soil biological activity. Conversely, limited evidence suggests that repeated applications of inorganic fertilizer nutrients can suppress production of certain soil enzymes that are involved in cycling of a given nutrient. The observed transitory decrease in crop productivity during conversion from chemical intensive input to alternative systems (greater reliance on biological resources) may be due to the initial diminished biological potentials of conventionally managed soils to efficiently cycle and mineralize organic nutrient sources. This review reaffirms the continuing need for the maintenance of existing long-term experimental sites and establishment of new studies in major agroecosystems throughout the world.     

Prenatal diagnosis of spina bifida aperta after first-trimester valproate exposure

In the context of a prospective study on the adverse effects of anti-epileptic drugs on fetal outcome, we evaluated our experience with prenatal diagnosis by ultrasonography and α- fetoprotein (AFP) determination in amniotic fluid. We compared these results with AFP values in maternal serum obtained prior to amniocentesis. From November 1985 to July 1990, amniocentesis at 16–18 weeks of gestation was performed in 267 pregnancies of 237 different women using anti-epileptic drugs. Among 92 pregnancies with maternal valproic acid use, five (including one concordantly affected monozygotic twin-pair) were terminated because of a spina bifida aperta, all prenatally diagnosed by AFP determination and acetylcholinesterase electrophoresis in amniotic fluid. The maternal serum AFP level was raised (⩾ 2.5 multiples of the median (MOM) for singleton pregnancies and ⩾ 4.5 MOM for twin pregnancies) in only two of these five affected pregnancies. We emphasize that maternal serum AFP levels may be unreliable for prenatal screening for fetal neural tube defects in women taking valproate and recommend that amniocentesis and fetal ultrasound examination should be offered directly.     

Differential predation by males on moulted females may explain the competitive displacement of Gammarus duebeni by G. pulex (Amphipoda)

Summary Several studies have reported the ability of Gammarus pulex to successfully compete with and ultimately displace G. duebeni in freshwater. These studies have been unable, however, to provide adequate explanations for this displacement based on mechanisms of exploitative competition and/or differences in the environmental tolerances of the species. The present study investigates the role of predation as an extreme form of interference competition between G. pulex and G. duebeni. The data presented show that: (1) given the opportunity, males of both species prey on females of the other species, but only on females that have recently moulted; (2) mate guarding in both species significantly reduces the incidence of predation on moulted females; (3) mate guarding by male G. pulex is more successful in reducing predation on moulted females than is guarding by male G. duebeni. We propose that differential predation rate on moulted females may constitute the primary mechanism by which G. pulex displaces G. duebeni. Offprint requests to: J.T.A. Dick