Effect of temperature and flooding duration on phosphate sorption in an acid sulphate soil from Vietnam

Phosphate sorption in soil is controlled largely by Fe-oxihydroxides, and so important changes in P dynamics are expected when the redox potential is modified. Such changes in P sorption when acid soil is flooded, as for rice cultivation, have been evaluated. Samples from an acid sulphate soil in the Mekong Delta of Vietnam were flooded for up to 56 d at 20°C and 30°C. Some of the samples incubated at 30°C were dried in open air for 30 d after flooding. Small redox potential (Eh<0) and pH>6 were rapidly reached in soil flooded at 30°C; less drastic reducing conditions (Eh ?0.2 V) and pH 4–5 occurred at 20°C. Phosphate sorption increased during flooding. The increase was twofold at 20°C, and 10-fold at 30°C. Phosphate sorption index decreased in the soil that was air dried after flooding at 30°C, but still remained two to three times greater than before flooding. These results were compared to the changes in oxalate-extractable Fe, i.e. poorly crystalline or amorphous Fe-oxihydroxides. The increase of P sorption per unit increase of oxalate-Fe was seven to eight fold larger at 30°C than at 20°C.     

Conservation strategies for endangered fish breeding and nursery grounds within the coastal wetlands of Nigeria

The Nigerian coastal system—estuaries, lagoons, creeks and wetlands—extends for a distance of approximately 850 km with the Niger Delta (area: 75 000 km²) dominating the entire ecosystem. Human activities—(oil exploration, haphazard mining of sand from coastal areas, sand filling of wetlands for industrial use, heavy pollution by industries)—severely destroyed the breeding and nursery grounds of commercial fish species between 1973 and 1992. As a result, fish landings from capture fisheries decreased from 500 000t in the late 1980s to the present 300 000t. With the Nigerian population increasing at a rate of 3%–4% per year, there is an urgent need for the Federal Government to protect the 850 km coastline, and the riverine wetlands. Conservation education should be vigorously pursued on the socio-economic benefits of coastal and riverine wetlands. The Federal Government should encourage States and Local Governments to enact environmental laws and regulations. Stiff penalties for violations should be vigorously enforced. Companies involved in exploitation and manufacturing in coastal areas should increase their funding of research directed at minimizing oil spillages and discharge of wastes in their areas of operation.     

Effects of supplemental feeding on gastrointestinal parasite infection in elk (Cervus elaphus): preliminary observations

The effects of management practices on the spread and impact of parasites and infectious diseases in wildlife and domestic animals are of increasing concern worldwide, particularly in cases where management of wild species can influence disease spill-over into domestic animals. In the Greater Yellowstone Ecosystem, USA, winter supplemental feeding of Rocky Mountain elk (Cervus elaphus) may enhance parasite and disease transmission by aggregating elk on feedgrounds. In this study, we tested the effect of supplemental feeding on gastrointestinal parasite infection in elk by comparing fecal egg/oocyst counts of fed and unfed elk. We collected fecal samples from fed and unfed elk at feedground and control sites from January to April 2006, and screened all samples for parasites. Six different parasite types were identified, and 48.7% of samples were infected with at least one parasite. Gastrointestinal (GI) nematodes (Nematoda: Strongylida), Trichuris spp., and coccidia were the most common parasites observed. For all three of these parasites, fecal egg/oocyst counts increased from January to April. Supplementally fed elk had significantly higher GI nematode egg counts than unfed elk in January and February, but significantly lower counts in April. These patterns suggest that supplemental feeding may both increase exposure and decrease susceptibility of elk to GI nematodes, resulting in differences in temporal patterns of egg shedding between fed and unfed elk.     

Preliminary evaluation of the suitability of Enterolobium cyclocarpum for use in intensive feed garden in southwestern Nigeria

The best method of establishment of Enterolobium cyclocarpum (enterolobium) and biomass yields and nutritive value under cutting were determined in three separate trials. Soaking in boiled water for 30 seconds gave the highest percent seed germination (76%) and most vigorous seedlings. Transplanted seedlings out-grew direct-seeded plants with 1.70 and 1.12 m, respectively, at six months after planting. Intra-row spacing did not significantly affect early growth of the plants. Cutting every 12 weeks gave the highest leaf (4.05 t/ha), stem (2.26 t/ha) and total (leaf + stem) dry matter yields. Cutting regimes did not significantly affect the crude protein and neutral detergent fibre content of the leaves which averaged 21.3 and 60.7%, respectively. This initial study suggests that enterolobium has a potential as a forage tree and should be further studied to understand its agronomy and feed value. This revised version was published online in June 2006 with corrections to the Cover Date.     

Cutting management of alley cropped leucaena/gliricidia-Guinea grass mixtures for forage production in southwestern Nigeria

A study was conducted at Fasola (7°45 N and 3°5 E) in southwest Nigeria to determine the best tree cutting scheme for forage production and the effects of hedge configurations on tree, grass and total forage productivity of 6–8-year-old leucaena (Leucaena leucocephala Lam. de Wit) and gliricidia (Gliricidia sepium Walp.)-Guinea grass (Panicum maximum Jacq. cv. Ntchisi) mixture. After a uniform cut at the end of January 1990 (mid-dry season), the trees were cut according to the following cutting regimes: one cut after a 12-month regrowth (12M); two cuts after three- and nine-month regrowth (3–9M); two cuts every six months (6-6M); two cuts after nine- and three-month regrowth (9-3M); three cuts, two cuts every three months and the third cut after a six-month regrowth (3-3-6M), and four cuts every three months (3-3-3-3M). Grass was cut every six weeks between April and October followed by a cut in January. The hedge configuration was either one or three hedgerows of mixed stands of leucaena and gliricidia. There were twice as many trees and one-third less grass in the triple than in the single hedgerow hedge configuration.The 3-3-3-3M, 9-3M and 3-3-6M cutting regimes produced the highest total forage (tree foliage + grass) dry matter yields (DM) of 6.54, 5.80 and 5.77 t DM ha^–1 annum^–1, respectively. The magnitude of the difference between the tree forage yields of the triple and single hedgerow plots (16%) did not reflect the theoretical difference in the number of trees (33%) in the two arrangements.     

Phosphorus sorption in soils of the Mekong Delta (Vietnam) as described by the binary Langmuir equation

Phosphate adsorption isotherms were determined for 20, mostly very acidic, soils from the Mekong Delta. The experimental data were well described by a binary Langmuir equation which considers two groups of sorption sites that differ in their P bonding energies. The maximum P-sorption capacities of these sites were related to the soil properties by simple linear correlation and by stepwise multiple regression. Results suggest that high energy sites are on Al-oxihydroxides or small Al-substituted Fe-oxides and, to a lesser extent, on poorly ordered Fe-oxihydroxides. On the other hand, the P-sorption capacity of low energy sites is mainly related to clay content, and it increases as pH decreases. These sites are also positively correlated with organic carbon and poorly crystalline Fe-oxihydroxides. However, as these two variables are closely correlated with each other, organic matter is likely to be considered as an indirect factor of P fixation through its association with Fe-oxihydroxides and not as an important source of P-sorption sites. The maximum sorption capacity, i.e. the sum of sorption capacities of the two groups of sites, is well described (r²= 0.88) by an equation that takes into account the four variables identified above: Al-bearing oxihydroxides, poorly ordered Fe-oxihydroxides, clay content and pH. Grouping the soils according to the orders of Soil Taxonomy, the P-sorption capacity increases in the following sequence: ultisols < entisols < inceptisols. A P concentration often considered adequate for plant nutrition is 0.2 mg P 1^?1 solution, and only the high energy sites are involved in sorption at that concentration. Thus an equation including only Al- and Fe-oxihydroxides could be used to fix P norms in these soils.     

Insect nicotinic acetylcholine receptor agonists as flea adulticides in small animals

Vo, D. T., Hsu, W. H., Abu‐Basha, E. A., Martin, R. J. Insect nicotinic acetylcholine receptor agonists as flea adulticides in small animals. J. vet. Pharmacol. Therap. doi: 10.1111/j.1365‐2885.2010.01160.x. Fleas are significant ectoparasites of small animals. They can be a severe irritant to animals and serve as a vector for a number of infectious diseases. In this article, we discuss the pharmacological characteristics of four insect nicotinic acetylcholine receptor (nAChR) agonists used as flea adulticides in dogs and cats, which include three neonicotinoids (imidacloprid, nitenpyram, and dinotefuran) and a macrocyclic lactone (spinosad). Insect nAChR agonists are one of the most important classes of insecticides, which are used to control sucking insects on both plants and animals. These novel compounds provide a new approach for practitioners to safely and effectively eliminate adult fleas.     

Production of catfish, Chrysichthys nigrodigitatus, in brackish water ponds in Nigeria using groundnut cake as supplemental feed

A comparative study of catfish, Chrysichthys nigrodigitatus (Lacépède) production was made in brackish water ponds near Lagos Lagoon using groundnut cake as the main supplementary feed. Data obtained included food conversion values, condition factor, length-weight relationships, survival and growth. Significant differences were recorded in lengths and weights of catfish given supplemental feed and those in natural ponds. In ponds without feed, catfish had a 114.1% gain in weight, and those given supplemental feed had a 858.1% gain in weight.