In our country, there are significant areas of soils with an alkaline reaction due to the presence of sodium in them - alkaline soils containing 10-20% sodium, and alkaline soils containing more than 20% sodium.
Solonetzes and solonetzic soils are characterized by poor physical properties: in the wet state they swell and float, and when dried they harden, form a crust and crack on blocks. Accordingly, their agricultural processing is very difficult, the alkaline reaction occurring in the soil is harmful to cultivated plants, and the dense solonetzic layer prevents the root system from penetrating deep into the soil. Crop yields on such soils are extremely low.
The most common way to improve the agricultural qualities of solonetzes and solonetzic soils is gypsum. When gypsum is introduced into the soil, soda in the soil solution is eliminated, and the sodium absorbed by the soil is displaced and replaced by calcium to form a neutral salt in the solution - sodium sulfate. As a result of gypsum treatment, the alkaline reaction of solonetzic soils is eliminated, the physical, physicochemical and biological properties of the soil are improved, and its fertility is increased.
If the salt layer has a shallow depth, gypsum is applied to the soil after plowing and cultivated. With a deeper layer, the entire dose of gypsum is dispersed and sealed with a plow with a skimmer. When the solonetzic horizon is located at a depth of 7-15 cm, gypsum can be applied for plowing or cultivation, as well as in two doses - a half dose for each of these tillages.
According to experiments, gypsum without irrigation increases grain productivity by an average of 3-6 c. Irrigation increases the efficiency of casting. The effect of gypsum increases significantly when incorporating it under deep plowing with the simultaneous introduction of manure, composts, and the use of green fertilizer. When gypsum, the effectiveness of both organic and mineral fertilizers increases.
The positive effect of gypsum on soil fertility is observed for 8-10 years, and due to the gradual interaction of gypsum with soil, its effect increases from year to year.
Gypsum is applied not only for chemical reclamation of solonetzes, but also with the aim of improving the nutrition of plants with calcium and sulfur on other soils, especially in the Non-Chernozem zone.
Gypsum containing calcium and sulfur as a fertilizer is used primarily under legumes - clover and alfalfa, which consume these elements much more than other crops. It is applied on grasses superficially, under other crops - to the soil in a dose of 3-4 centners per 1 ha. The positive effect of gypsum on the growth, development and productivity of plants on acidic soils is due not only to an improvement in the nutrition of calcium and sulfur, but also to an increase in the resistance of plants to acidity with an increase in the concentration of calcium in the soil solution, and an improvement in the availability of potassium. Clover hay yield increase from gypsum application on sod-podzolic soils is 7-10 centners, on gray forest soils and leached chernozems up to 6-7 centners per 1 ha.
Thus, despite the development of high-tech methods to improve soil quality, gypsum still plays a crucial role in agriculture and is in great demand by agricultural enterprises.