Papers by Roelof Westerhof
Carbon Sequestration in the Biosphere, 1995
Water balance, respiration and immobilisation in relation to deltamethrin poisoning and physical conditions in the epigeal spider Oedothorax apicatus
Pesticide Science, 1995
The effect of a pyrethroid insecticide, deltamethrin, on water loss, metabolic rate and immobilis... more The effect of a pyrethroid insecticide, deltamethrin, on water loss, metabolic rate and immobilisation was studied, using the epigeal spider Oedothorax apicatus (Blackwall) (Linyphiidae) as a test species. Water loss was measured gravimetrically at different temperatures, air humidities, and doses of deltamethrin. Metabolic rate and immobilisation were measured at different temperatures and doses. Immobilisation was measured at different relative humidities and temperatures. Water loss due to evaporation increased linearly with vapour pressure deficit. The slope of the latter relationship increased with temperature, indicating an increase in cuticle permeability with temperature. In addition to water loss by evaporation, deltamethrin treatment induced water excretion. This was positively related to dose and temperature, but independent of air humidity. Metabolic rate increased with temperature and dose. Immobilisation was highest at low temperatures in combination with low air humid...
Prolonged leaching of mineral forest soils with dilute HCl solutions: the solubility of Al and soil organic matter
European Journal of Soil Science, 1998
Long‐term acidification has been shown to result in a considerable decrease in the amount of orga... more Long‐term acidification has been shown to result in a considerable decrease in the amount of organically bound soil Al and in a gradual decrease in the solubility of Al. We examined the solubility of soil organic matter (SOM) and Al in four acid mineral soils (one Arenosol Ah, two Podzol Bh, and one Podzol Bs) as they were leached sequentially using a solution containing 0.001 m HCl and 0.01 m KCl. The acid leaching resulted in relative decreases in Al that were 2–6 times greater than for organic C. The organic C and Al dissolved by the acid leaching originated mainly in the pyrophosphate‐extractable fraction of the elements. Protonation seems to be a major mechanism in stabilizing the residual SOM, as indicated by small changes in effective cation exchange capacity with the degree of acid leaching. In the samples of Podzol Bh and Arenosol Ah soils the solubility of Al (defined as log10{Al3+} + 1.5pH) in equilibrium suspensions (0.01 m KCl) was closely related to the ratio of pyroph...
Biology and Fertility of Soils, 1998
The effect of land use on the availability of nitrogen (N) was studied by separating total N into... more The effect of land use on the availability of nitrogen (N) was studied by separating total N into a labile and a stable fraction by oxidation and extraction of labile N with KMnO 4. The nitrogen management index (NMI) was calculated following the method of Blair et al. (1995) for the carbon management index. In all systems, labile N released by KMnO 4 was a better indicator of N availability than total and stable N. The NMI was a good indicator of N availability but gave no information about the total amount of N. In land use system analysis, total N and labile N can be used together as a simple and rapid way to evaluate the N status of the soil. Legume-based pastures specifically increased the amount of labile N. Although soybeans had a dominant role in the continuous cropping systems studied, the total N contents of these systems were lower than those of the natural Cerrado. The availability of N under legume-based pastures and legume-based pasture-crop rotations was higher than under the natural Cerrado and the continuous cropping systems.
Soil organic carbon, carbohydrates, amino sugars, and potentially mineralizable nitrogen under different land-use systems in Oxisols of the Brazilian Cerrados
Aggregation studied by laser diffraction in relation to plowing and liming in the Cerrado region in Brazil
Geoderma, 1999
... Geoderma Volume 90, Issues 3-4, July 1999, Pages 277-290. ... The effective cation exchange c... more ... Geoderma Volume 90, Issues 3-4, July 1999, Pages 277-290. ... The effective cation exchange capacity at soil pH (ECEC) was calculated as the sum of Na, K, Ca, Mg and Al extracted by NH 4 ClBaCl 2 solution (Amacher et al., 1990). ...
Short term effects of land use systems on nutrient availability and structural stability in the Cerrado region in Brazil : some sensitive parameters for soil quality
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Papers by Roelof Westerhof