Gypsuming of Soil

the addition of gypsum to soil to eliminate excess alkalinity, which is dangerous to many crops; a chemical method of improving solonets and alkaline soils. Gypsuming is based on the replacement by calcium of the sodium absorbed by the soil, thereby improving the soil’s unfavorable physicochemical and biological properties and increasing its fertility. The amount of gypsum, which is determined by the quantity of sodium in the root zone of the soil that must be replaced by calcium, ranges from 3—4 to 10-15 tons per hectare (ha); the largest amount is required by white alkali soils. The gypsum is applied twice—before plowing and afterward, during cultivation. In alkaline soils, which contain less sodium than solonetses, gypsum is applied to the rows in quantities of 3-4 centners per ha along with the seeds. Gypsuming is performed in conjunction with various farming practices: deep plowing (to 40-50 cm) with mixing of the solonets layer (to enable the gypsum in the subsoil to reach the plowed layer), irrigation, addition of organic fertilizers, snow and thaw-water retention, and planting of perennial grasses.

Raw-ground gypsum (from natural deposits), phosphogypsum (wastes from the manufacture of fertilizers), and wastes from the soda industry are the principal kinds of gypsum used to treat soil. The time required to turn solonetses into arable soils by gypsuming (the reclamation period) is 8-10 years without irrigation and 5-6 years with irrigation. The average increase in grain yield after the addition of gypsum is 3-6 centners per ha in the chernozem zone (without irrigation) and 2-7 centners per ha in the chestnut soil zone. The efficacy of gypsum treatments increases on irrigated lands.