Effects of primary tillage systems on soil physical properties and grain sorghum productivity after rice in paddy-derived soils under arid conditions of the Kyzylorda region, Kazakhstan

This study was conducted to evaluate the effects of different primary tillage systems on selected soil physical properties and grain sorghum productivity in paddy-derived meadow-marsh soils of the Kyzylorda region, Kazakhstan. The experiment was carried out during the 2024 and 2025 growing seasons at the scientific station of the Kazakh Research Institute of Rice Growing named after I. Zhakhayev. Three tillage treatments were compared: moldboard plowing (25–27 cm), non-inversion tillage (14–16 cm), and sweep plowing (13–15 cm). The study assessed pre-sowing soil moisture, bulk density, surface roughness, aggregate-size distribution, soil structure coefficient, field emergence, plant survival, green biomass yield, and grain yield. The two experimental years differed in weather conditions, with 2025 being warmer and drier than 2024 during critical growth stages. Tillage significantly affected both soil physical properties and crop performance. Sweep plowing and non-inversion tillage conserved more pre-sowing moisture than moldboard plowing, while moldboard plowing resulted in lower bulk density and greater surface roughness. Reduced tillage treatments increased the proportion of 25–10 mm aggregates, whereas moldboard plowing produced a slightly higher soil structure coefficient. Sweep plowing provided the highest field emergence in both years, but moldboard plowing resulted in the highest plant survival, green biomass yield, and grain yield. Averaged across years, moldboard plowing produced the highest grain yield (2.8 ± 0.18 t ha⁻¹), whereas non-inversion tillage and sweep plowing reduced yield by about 0.4–0.5 t ha⁻¹. The results indicate that reduced tillage was advantageous for pre-sowing moisture conservation and early establishment, whereas moldboard plowing created a more favorable root-zone environment for final crop productivity. Under the paddy-derived soils and arid rice-rotation conditions of the Kyzylorda region, moldboard plowing to 25–27 cm was the most effective tillage option for stable grain sorghum production.