Impact of Organic Ameliorants on Grey Soil Fertility

Abstract

The study aimed to assess the effectiveness of organic-biological ameliorants for restoring the fertility of light grey soils in the Turkestan region of Kazakhstan, which are characterised by low humus content (0.8-1.1%) and high alkalinity (pH 7.9-8.3). The field experiment was conducted on an area of 2304 m² using four treatment options: control (variant 1 only mineral fertilisers) and three variants with different doses of compost (variants 2-4: 2.5-3.5 t/ha) in combination with the microbial strain Bacillus subtilis KAZ-12. The humus content was determined by the Turin method at the depths of 0-20 cm, 20-40 cm and 40-60 cm before and after the growing season. The highest efficiency was demonstrated by variant 4 with 3.5 t/ha in autumn and 0.5 t/ha in spring, which ensured an increase in the humus content in the top layer by 9.1% (from 0.756% to 0.825%) and a decrease in seasonal fluctuations to 0.021% compared to the control (0.754%). The aggregate structure of the soil was also improved (growth of stable aggregates by 12-15%), and microbiological activity increased. The obtained results prove that the combined use of organic ameliorants with microbial preparations is a promising direction for stabilising the humus profile of grey soils under irrigated agriculture. This strategy not only restored soil fertility but also reduced dependence on mineral fertilisers, which is especially important for regions with arid climates. The study confirms the need to adapt biological technologies to local soil and climatic conditions to achieve a sustainable effect. The practical significance of the study is the development of scientifically based recommendations for the use of organic-biological ameliorants to improve the efficiency of soil fertility management in areas of risky farming.