Description of practice
Alkalinity management is needed in agricultural soils with pH >8.4. This occurs in poorly drained soils where evaporation concentrates sodium bicarbonate (alkali) at or near the soil surface. Management consists of improving drainage and/or acidification (either by applying calcium as gypsum or by applying an acid to dissolve calcium already in the soil). This is followed by leaching of the salts.
|Examples of how to use alkalinity management
(see Note below)
Calcareous soils management
Water-logged fields with high pH are reclaimed for cultivation by a combination of drainage channel construction and injecting ammonia as an acidifying agent to dissolve calcium carbonates.
Gypsum (calcium sulphate) is applied to alkaline soils to provide soluble Ca2+ to displace Na+ and maintain infiltration rates. Mixing gypsum to a depth of 15 cm is more effective than surface application. Flushing of salts is also needed.
Applying elemental sulphur, aluminum sulphate or pyrite
Sulphur is applied to alkaline soils to lower the pH by biological oxidation, producing sulphuric acid. Cost-effectiveness may be an issue, but sulphur and sulphates may reduce pH faster than gypsum.
Note: Most of the Further information links are to a full description of the example in the WOCAT database. However sometimes the link may be to similar practices or a research paper. Occasionally the link is to a commercial product in which case it should be understood that this does not imply any endorsement of the product by iSQAPER.