The relative importance of facilitation and competition between pairwise plants across abiotic stress gradients as predicted by the stress-gradient hypothesis has been confirmed in arid and temperate ecosystems, but the hypothesis has rarely been tested in tropical systems, particularly across nutrient gradients. The current research examines the interactions between a pioneer shrub Rhodomyrtus...

The rate of volatilization of dinoseb may depend on soil acidity, temperature, surface soil moisture, the method of application, and the type of formulation (Kaufman 1976). Cohen et al. (1984) reported a volatilization half-life of 26 d. The significance of volatilization has been evidenced by the killing of plants by dinoseb vapours (Davis et al. 1954). Photodegradation is a major fate process...

In greenhouse trials, 21 strains of slow-growing rhizobia were tested for symbiotic effectiveness and ability to nodulate three varieties of cowpea, Vigna unguiculata L. Walp. in two Ultisol subsoil samples, each adjusted to pH 4.6 and pH 6.0-6.2. The results confirmed that cowpea rhizobia contain a large and perhaps continuous variation in symbiotic tolerance of soil acidity. Some strains comb...

Al toxicity is a severe impediment to production of many crops in acid soil. Toxicity can be reduced through lime application to raise soil pH, however this amendment does not remedy subsoil acidity, and liming may not always be practical or cost-effective. Addition of organic acids to plant nutrient solutions alleviates phytotoxic Al effects, presumably by chelating Al and rendering it less to...

Rhizobia are bacteria that can fi xate atmospheric nitrogen in association within the root or the stem nodules of legume plants and transform atmospheric nitrogen to ammonia. Soil environmental conditions are critical factors for the persistence and survival of rhizobia in the soil. Th e changes in the rhizosphere environment can aff ect both growth and saprophytic competence, which will infl u...

The review is an attempt to specify particular features of the biological processes involved in the nitrogen cycle as they occur in the following categories of West African ecosystems : flooded rice .fields, rain-fed agroecosystems, and forests. In rice fields in Senegal the nitrogen input through blue-green algae was reported to be in the range -, of 1-30 kg ha-' yr-'. Figures for heterotrophi...

Investigations were performed on soils of different acidity, ranging in the pH interval 4.65–5.80 (in water). Changes of the mineral nitrogen forms in the examined soils were studied by applying short-term incubation experiments performed under aerobic conditions, with a humidity of 30 % and a temperature of 20 °C, both with and without the addition of 100 and 300 ppm NH4–N. The results of the ...

The fiterature of soil bacteriology is replete with assertions to the effect that soil bactena of value for the maintenance of an appropriate soil condition need an alkaline medium for their proper development. This has been repeatedly emphasized, particularly in connection with the nitrifying and the nltrogen-fixing flora of the soil. Actual evidence substantiating such assertions has never be...

As atmospheric CO2 concentration increases, many experiments have been carried out to study effects of CO2 enrichment on litter decomposition and nutrient release. However, the result is still uncertain. Meanwhile, the impact of CO2 enrichment on nutrients other than N and P are far less studied. Using open-top chambers, we examined effects of elevated CO2 and N addition on leaf litter decompos...