Alkaline soils are defined as those that are saturated with salts and have high soil pH values. Let's consider the composition, what compounds and elements alkaline soils consist of, their reaction, the causes of salinity, the main signs by which they can be identified, the vegetation of alkaline soils. What methods can be used to lower the high pH of this type of soil so that it becomes suitable for growing plants.
What it is?
This is the name given to soils that have an alkaline reaction. If it is 7-8; then the soil is slightly alkaline, if the pH is 8-8.5 - medium alkaline, and pH 8.5 or more - highly alkaline.
Alkalinity is determined by the high content of salt compounds that are deposited in the soil layer. Due to the increased concentration of the elements calcium, magnesium and sodium, alkaline soils are generally unfavorable for the development of many plant species.
Causes of soil salinity
Saline soils are divided into 2 types: solonchaks and solonetzes. In the first, salts are distributed throughout the profile. In the second, they are not present in the upper layer, but the lower layer is saturated with salts, which is why the soil properties are reduced, because there is a lot of sodium in the absorbent complex. The element creates unfavorable properties for plants.
Land salinization occurs due to arid climates in which the evaporation of moisture from the surface exceeds the volume of water entering the interior during the leaching process. Salts rise along with groundwater; after the water evaporates, they remain in the fertile layer. In winter, salts are washed out to a certain depth, and in summer they rise upward.
Soils are considered very slightly saline if they contain 0.2-0.25 g of salts per 100 g, and slightly saline - 0.25-0.50. If they contain 0.5-0.7 g, then these are moderately saline soils, if 0.7-1 - they are already saline soils.
Main features
Usually alkaline soils are low fertile, they have poor physical properties and poor chemical properties. compound. They are difficult to handle, wet, sticky and viscous, and do not allow water to pass through well.
You can determine alkaline soils by taking a small ball of earth and sprinkling it with vinegar.If foam appears on the soil and it begins to hiss, then these signs of an acid-alkali reaction indicate that the soil is alkaline. You can also determine acidity using litmus paper - if the soil solution turns it blue, then the soil is alkaline.
What can grow in alkaline soils?
Despite unfavorable growing conditions for plants, some species can grow on alkaline soil. The variety depends on the amount of salts contained in the soil.
Which ones cannot tolerate salt saturation?
Wild plants such as clover cannot grow on salty soils; fruit plants include pome and stone fruits, viburnum, strawberries and roses, citrus fruits and avocados. As for flowers, you cannot grow hydrangeas, azaleas, conifers, blueberries and lingonberries on them. Cultivated species will not produce large yields even in well-cultivated and fertilized soil if it contains a lot of salts.
Moderately resistant to salinity
Sunflower, flax, corn, fescue and ryegrass, variegated sweet clover and alfalfa can tolerate alkaline soils, that is, pastures and industrial crops can grow in such areas with not the most favorable conditions.
Vegetables that carry alkali include nightshades, cucumbers, onions, root vegetables, cabbage, legumes and pumpkins. They can be sown in not very saline soil. Just like table and wine grapes, pomegranates, and figs. Among the ornamental crops that grow on such soils are juniper and thuja.
Resistant plants
Vegetables include beets, asparagus and spinach, kale. From fruit and berry bushes - date palm and oleander or indoor plant. Of the perennial plants that can withstand alkali, tall fescue, grasshopper, commonweed, and pigwort can withstand alkali.
Methods for Reducing High pH
Gypsum, iron sulfate, and sulfur are added to alkaline soils. It is necessary to add organic matter and mineral fertilizers, since the nutritional value of such soils is low. It is necessary to use acidifying fertilizers, organic fertilizers - sawdust and manure, and sow green manure, which will increase the level of humus. How much fertilizer you need to apply depends on the alkalinity level. So, for example, 2-10 tons of gypsum need to be applied per hectare.
Phosphogypsum can be used for alkalization. In addition to calcium sulfate, it contains impurities of fluorine and sulfuric acid. The dosage of gypsum on solonetzes is on average 0.5 kg/m2, on not very saline soils - 0.2 kg/m2 of gypsum or phosphogypsum.
To improve saline and alkaline soils, it is necessary to carry out deep plowing with the introduction of reclamation additives. Irrigation is also necessary, especially in dry regions.
Slightly alkaline soils on private plots can be improved by surface digging, with the addition of large volumes of organic fertilizers in combination with the cultivation of green manure. It will take several years of improvement to see results.
Alkaline soils do not have good characteristics; the greater the alkalinity and salinity, the less suitable they are for growing crops. In areas with slightly alkaline soil, many cultural species can be grown; in areas that are too saline, it will not be possible to obtain even an average harvest.Alkaline soils need to be improved by applying gypsum, fertilizers and carrying out agrotechnical measures.
