Agroreclamation characteristics of southern chernozems in connection with irrigation

Abstract

Abstract. Sustainable highly productive agriculture in the arid steppe zone of Western Siberia is possible only on the basis of optimizing the water regime of soils. The relevance of irrigation is increasing due to the degradation of the soil cover, the geopolitical and resource potential of the territories and the fundamental change in the development strategy of Russia. Light soils prevailing in the Central and Northern Kulund, widely used for crop production, are characterized by a weak water-retaining capacity and require additional in-depth study of the features of reclamation properties. The purpose of the research is to solve scientifically and practically relevant problems of agrohydrophysics of southern light loamy chernozems in connection with the development of soil-saving irrigation technology based on knowledge about the processes of movement, moisture retention in the profile and the limits of its availability to plants. Methods. Field and laboratory methods of soil research were used: morphological study, determination of physical and water properties of the soil according to generally accepted methods. Results. Ameliorative properties of the southern light loamy chernozems of the Northern Kulunda have peculiarities in the granulometric composition, where sandy fractions of 1–0.25 and 0.25–0.05 mm in size predominate and make up to 46–77 % of all particles, providing a weak water-retaining capacity, soluble salts. Good drainage of the soil profile is provided by the underlying layers of sandy loam, loam, sand, up to 3–8 m thick. The reduced porosity of soil-forming and underlying rocks (up to 35.4–40.1 %), along with a high density of composition, ensures non-sagging irrigation of these soils. Weak structure along with favorable microaggregation create favorable water-physical properties. A significant part of the pores (11.9–37.3 %) along the profile in the state of the lowest moisture capacity (HB) is free from water. Water permeability and filtration are increased (from the surface at 1, 2, 3 hours, respectively, 38.6–95.5 mm; 34.0–51.4 and 31.1–49.9 mm). Moisture reserves at wilting moisture (WM) in layers 0–50 cm, 0–100, 0–200 cm are 45 mm and 90.82 mm, respectively. HB on arable land in the 0–50 cm layer is 114.7 mm (15.5 %), in the 0–100 cm layer it reaches 218.7 mm (14.2 %). Under natural conditions, the moisture content of these soils does not reach the HB value even in spring. The range of active moisture (AWM) is narrow, which must be taken into account, together with the characteristics of its movement, when calculating irrigation regimes for a particular soil. The scientific novelty. A complete description of the physical and hydrological properties that are in dire need of optimization of the water regime of southern light loamy chernozems is presented, which is necessary for further in-depth study of the behavior of moisture in their profile, the limits of its availability to plants and the development of modern soil protection technology for selective and local irrigation.