Abstract
Phosphorus deficiency and declining organic matter limit crop productivity in Northern Kazakhstan’s chernozem soils. This study evaluates whether the combined application of phosphorus fertilizer and an ash-carbon amendment from industrial by-products can improve soil fertility and barley yield. In a three-year field experiment (2018–2020), four P rates (1/10, 1/5, 1/2, and the full recommended dose, Prec) were tested with 100 kg ha−1 of ash–carbon product (“Agrobionov”). Across growth stages, we measured cellulolytic microbial activity, water-stable soil aggregates (%WSA), and grain yield. Relative to the control, P + ash–carbon increased microbial activity by up to 57.6% and %WSA by up to 76%. The highest yield (1.32 t ha−1) occurred with Agrobionov + ½ Prec, a 51.7% increase over the control. These results indicate that pairing moderate P rates with an ash–carbon amendment enhances soil biological and physical properties and improves yield in P-deficient chernozems, supporting the sustainable use of industrial by-products as cost-effective soil amendments. Future work should assess long-term effects on C sequestration, nutrient cycling, and economic feasibility.