Transcript No Slide Title

USE OF CHEMICALS IN SWC
Soil chemical treatments
Wetting agents
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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-43925/
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Nonionic surfactants
• Nonyl Phenol Ethoxylates
• Alcohol Alkoxylates
• lower molecular weight chemcials may be phytotoxic
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Polymeric nonionic surfactants
Ultra-penetrants
Hydrophilic soil conditioners
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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
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Polyvinyl acetate effective in semi-arid areas - reduced
runoff by 84 to 97% in one experiment.
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
Natural materials to improve structure
Calcified Seaweed
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dead remains of calcareous red algae (Rhodophyta)
improves clay structure - flocculation
improves water holding capacity – silt size
Coir
PVA
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
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
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
Chemical treatment of plants
Albedo increasers (reflective transpiration suppressants)
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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