Effects of Ameliorants on the Microbial Diversity of Chestnut Soils Under Periodic Flooding in Western Kazakhstan

Aliya Nagiyeva, Marat Ongayev, Rashit Sh. Dzhaparov, Serik Denizbayev, Yergali Ayupov, N.M. Umbetkaliyev, Динара Салимова

Agrochemicals, 2026

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DOI 10.3390/agrochemicals5030031
Data confidence 70 medium
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Abstract

This paper presents the results of studying the effects of chemical amelioration and periodic flooding and its effects on the agrochemical properties of chestnut soils, the structure of microbial communities, and the productivity of natural grass stands in Western Kazakhstan. The research was conducted in 2024–2025 at a site within the Ural-Kushum irrigation and water-supply system, applying gypsum (6000 and 12,000 kg/ha) and elemental sulfur (3000 and 6000 kg/ha). It was found that of ameliorants altered the agrochemical parameters of the soil, particularly in the upper soil layer (0–20 cm): pH decreased, while the content of nitrate nitrogen, available phosphorus, and sulfur increased, whereas the potassium content showed comparatively minor changes. The maximum effect was observed at application rates of 12,000 kg/ha for gypsum and 6000 kg/ha for sulfur. High-throughput sequencing revealed that microbial communities consisted of 97.70% bacteria, with approximately 2.20% of taxa remaining unclassified at the kingdom level. In the control treatment, Pseudomonadota (43.63–47.88%), Acidobacterium (13.09–18.11%), Bacillota (9.74–13.15%), and Acidobacteria (up to 33.10% in the top layer, with a sharp decline down the soil profile) dominated. The application of gypsum and sulfur induced a redistribution of taxa: a decrease in the abundance of Pseudomonadota in the top layer, an increase in Acidobacterium and Verrucomicrobium, and a reduction in Acidobacterium in deeper horizons, especially at higher rates of ameliorants. The productivity of the grass stand increased under the influence of the ameliorants, as evidenced by a growth in plant height and hay yield, the maximum values reaching 2060 kg/ha with the application of 6000 kg/ha of gypsum. A strong correlation was observed between grass stand density and yield (r = 0.99). The obtained results confirm that chemical amelioration under periodic flooding conditions exerts a comprehensive influence on soil agrochemical properties, microbial community structure, and grass stand productivity.