In Russia, there are significant areas of alkali (with sodium content of up to 10-20%) and saline soils (more than 20% of sodium).
Saline and alkali soils have poor physical properties: when wet, they swell and get flooded, and when dried, they harden, form a crust, and crack into lumps. This greatly complicates their agricultural processing. Moreover, the alkaline reaction occurring in the soils is harmful to cultivated plants, and the dense saline layer prevents deep penetration of the root system. The yield of agricultural crops on such soils is extremely low.
The most common way to improve the agricultural qualities of alkali and saline soils is gypsuming. Application of gypsum to the soil allows to eliminate sodium carbonate from the soil solution. At the same time, sodium absorbed by the soil is displaced and replaced by calcium with the formation of a neutral salt in the solution — sodium sulfate. Gypsuming neutralizes the alkaline reaction in the soil, improves its physical, physico-chemical, and biological properties, and increases its fertility.
If the alkali layer is at a shallow depth, gypsum is applied to the soil after plowing and buried with a cultivator. With a deeper alkali layer, the entire dosage of gypsum is dispersed and buried using a plow with a skimmer. When the alkali claypan is located at a depth of 7-15 cm, gypsum can be applied during plowing or cultivation, as well as in two steps - half the dosage for each of these soil treatments.
According to the experimental data, gypsuming without irrigation increases the grain yield by an average of 3-6 centners. Irrigation increases the efficiency of gypsum treatment. The effect of gypsum increases significantly when it is buried during deep plowing with the simultaneous introduction of manure, composts, and green manure. Gypsum boosts the effectiveness of both organic and mineral fertilizers.
The positive effect of gypsum on soil fertility is observed for 8-10 years, and due to the gradual interaction of gypsum with the soil, its effect increases year after year.
Gypsum is applied not only for the chemical amelioration of saline soils, but also to improve the nutrition of plants with calcium and sulfur on other soils, primarily in the Non-Chernozem zone.
Gypsum with calcium and sulfur in its composition is used as a fertilizer, primarily for legumes (clover and alfalfa) which consume more of those micronutrients compared to other crops. On grasses, it is applied superficially. For other crops, gypsum is applied to the soil at a dosage of 3-4 centners per ha. The positive effect of gypsum on the growth, development, and yield of plants on acidic soils is due to improved supply of calcium and sulfur and an improvement in plant resistance to acidity following an increase in the concentration of calcium in the soil solution and the availability of potassium. The increase in the yield of clover hay after the application of gypsum is 7-10 centners per ha on soddy-podzolic soils, and up to 6-7 centners per ha on gray forest soils and leached chernozems.
Thus, despite the emergence of high-tech ways to improve soil quality, gypsum still plays a crucial role in agriculture and is in demand among agricultural enterprises purchasing large quantities of this substance.