1. USE OF CHEMICALS IN SWC Soil chemical treatments Wetting agents hydrophobic soilshydrophobic soils allow infiltration on soils which are naturally resistantallow infiltration on soils which are naturally resistant surfactants – reduce surface tensionsurfactants – reduce surface tension Anionic surfactantsAnionic surfactants Ammonium Lauryl Ether SulphatesAmmonium Lauryl Ether Sulphates Sodium LignosulphonatesSodium Lignosulphonates Sodium alkyl sulphosuccinatesSodium 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-penetrantsUltra-penetrants

3. Hydrophilic soil conditioners Hydrophilic soil conditioners absorb many times their own weight of water but release it at the range of potentials prevailing in the soilabsorb many times their own weight of water but release it at the range of potentials prevailing in the soil increase AWC, reduce drainage losses,increase AWC, reduce drainage losses, e.g. Agrosoak and polyacrylamidee.g. Agrosoak and polyacrylamidehttp://www.nal.usda.gov/wqic/Bibliographies/eb9614.html Polyvinyl acetate effective in semi-arid areas - reduced runoff by 84 to 97% in one experiment.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)dead remains of calcareous red algae (Rhodophyta) improves clay structure - flocculationimproves clay structure - flocculation improves water holding capacity – silt sizeimproves water holding capacity – silt sizeCoirPVA

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

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

8. Infiltration inhibitors 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)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) waxwax bitumenbitumen

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