Problems of irrigated land fertility in the post-industrial period of land reclamation development
Abstract
Purpose: to study the factors determining the risks of declining irrigated land fertility in the post-industrial period of land reclamation development. Materials and methods. The research materials are the results of monitoring irrigated and adjacent non-irrigated lands, for the organization of which dynamic sites located in the agrolandscapes of the dry steppe and semi-desert zones of the Lower Volga region are used. A total of 15 dynamic sites were laid out. In the methodological aspect, the transect-catenar method, comparison of monitoring indicators in the natural environment and on the used sites, as well as an assessment of long-term trends in changes of soil fertility elements, taking into account anthropogenic load, is used. Results. Compared with the natural background, the organic matter content is reduced by 0.20–0.89 % on irrigated land sand by 0.49–1.48 % on dry lands. In experiments with agricultural crops (corn for silage), irrigation ensured a non-negative humus balance (plus 0.297 t/ha), however, which turned out to be lower than under natural conditions (plus 0.428 t/ha). The decomposition rate of plant residues (soybean straw) under irrigation increased by 1.4–2.2 times compared to dry farming. The zonal problem of carbonation of the arable horizon worsens the conditions of water exchange and actualizes the problem of soil compaction: from 1.14–1.40 t/cub. m in the 0–0.30 m layer to 1.40–1.60 t/cub. m in the subsoil horizons. Research has confirmed the trend of redistribution of water-soluble salts to deeper horizons during irrigation. Data, confirming the development of soil alkalinization processes when irrigated with water with a salinity of 1.01–1.12 g/l and a SAR of 3.1, which also indicates the inadequacy of the SAR concept, were obtained. Conclusions: fertility problems in irrigated lands in the post-industrial period of land reclamation development are primarily associated with zonal risks, a deficit in the organic matter balance, and the need to optimize the soil water regime.