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USE OF CHEMICALS IN SWC Soil chemical treatments Wetting agents hydrophobic soils

USE OF CHEMICALS IN SWC Soil chemical treatments Wetting agents hydrophobic soils allow infiltration on soils which are naturally resistant surfactants – reduce surface tension Anionic surfactants Ammonium Lauryl Ether Sulphates Sodium Lignosulphonates Sodium alkyl sulphosuccinates

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USE OF CHEMICALS IN SWC Soil chemical treatments Wetting agents hydrophobic soils

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  1. USE OF CHEMICALS IN SWC • Soil chemical treatments • Wetting agents • hydrophobic soils • allow infiltration on soils which are naturally resistant • surfactants – reduce surface tension • Anionic surfactants • Ammonium Lauryl Ether Sulphates • Sodium Lignosulphonates • Sodium alkyl sulphosuccinates • http://www.soil.ncsu.edu/publications/Soilfacts/AG-439-25/

  2. Nonionic surfactants • Nonyl Phenol Ethoxylates • Alcohol Alkoxylates • lower molecular weight chemcials may be phytotoxic • Polymeric nonionic surfactants • Ultra-penetrants

  3. Hydrophilic soil conditioners • absorb many times their own weight of water but release it at the range of potentials prevailing in the soil • increase AWC, reduce drainage losses, • e.g. Agrosoak and polyacrylamide • http://www.nal.usda.gov/wqic/Bibliographies/eb9614.html • Polyvinyl acetate effective in semi-arid areas - reduced runoff by 84 to 97% in one experiment.

  4. Structure improving chemicals • very high molecular weight, long-chain, polymeric, organic compounds, • bind particles together and form stable aggregates • natural polysaccharides, • anionic and cationic polymers, • polyacrylamides • urea-poly-condensate

  5. Natural materials to improve structure • Calcified Seaweed • dead remains of calcareous red algae (Rhodophyta) • improves clay structure - flocculation • improves water holding capacity – silt size • Coir • PVA

  6. Reducing percolation losses • Insert impermeable membrane below root zone, • e.g. plastic, bitumen, rubber • expensive • risk of salinisation/drainage problems increased • may reduce fertiliser requirement by reducing percolation losses

  7. Evaporation suppressors • Emulsion of water and oil/wax. e.g. hexadecanol, bitumen, asphalt, latex • polydimethylsiloxane • bind soil, reduce wind & water erosion, & evaporation • may increase runoff, possibly useful for Water Harvesting (see later) • may cause pollution problem • expensive

  8. Infiltration inhibitors • chemicals, e.g. salt sometimes used to increase runoff from unplanted part of catchment to increase effective rainfall on planted part (see section on water harvesting) • wax • bitumen

  9. Chemical treatment of plants • Albedo increasers (reflective transpiration suppressants) • white to reflect solar radiation • kaolin - cuts solar heating & air turbulence • may reduce insect pest damage • must be non-toxic/palatable • may reduce yields by clogging stomata, or reduction of photosynthesis • Metabolic transpiration suppressants • physical barriers • wax, silicone, latex sprayed onto leaves • systemic (herbicides) • alachlor • atrazine

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