ISSN:
1365-2389
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Geosciences
,
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
The controlled release of agrochemicals from capsules, uniformly distributed in the soil, and their spread in the soil profile by diffusion and convection, coupled with first-order degradation, are studied theoretically. This transient transport is formulated mathematically as an approximate description of two simultaneous processes: (1) local release from the capsule, described as taking place in a confined, spherical soil domain, with a quasi-steady-state diffusional spread in each time step and (2) the vertical spread of the released material in the soil profile, described by the convection-dispersion equation including a source term for the solute transport, coupled with the Richards’ equation for the water flow. These processes of release, spread and degradation are simulated for realistic field conditions to study the effects of management practices and environmental conditions on the release rate. For a given amount of chemical per unit area, the rate of release increases with increasing number of capsules and with increasing depth of incorporation. Increasing irrigation intensity also enhances the release rate, as well as increasing the time interval between irrigations for the same seasonal amount of water applied. Under a given irrigation regime and incorporation practice, the rate of release increases progressively from coarse to fine-textured soils. The amount of released agrochemical remaining in the target zone after a certain time is compared with the amounts of a similar non-encapsulated agrochemical and of an inert tracer retained in the soil. The encapsulated material always persists longer, to an extent depending on the above-mentioned conditions.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1365-2389.1997.tb00218.x
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