Abstract
A two-year randomized field trial was conducted to evaluate the effects of foliar bio-based fertilization on the growth, productivity, grain quality, and soil health of spring wheat (Triticum aestivum L.) under semi-arid conditions in Northern Kazakhstan. Four treatments were compared: T0 (100 kg Ammophos, mineral fertilizer control), T1 (50 kg N14P23 + biotreatment), T2 (25 kg N14P23 + biotreatment), and T3 (biotreatment only), where biotreatment consisted of biosulfur organic fertilizer and amino-acid biostimulants applied foliarly at 1 L/ha. Growth parameters, including plant height, root length, plant density, and productive tiller count, were significantly improved across all biotreated plots relative to the control. T1 achieved the highest biological and grain yields at 28.2 and 24.3 dt/ha, respectively. Grain protein content was significantly elevated in all experimental treatments. Normalized Difference Vegetation Index (NDVI) values were consistently higher in T1 and T2 at all measured growth stages, indicating improved chlorophyll content and overall plant health. Soil microbial activity, assessed via fluorescein diacetate (FDA) hydrolysis, was highest in T2, reflecting enhanced enzymatic function and soil biological activity under reduced mineral fertilizer input. Overall, T1 (50 kg N14P23 + biotreatment) is recommended as the most effective strategy, combining high productivity, improved grain quality, and enhanced soil health while reducing dependence on conventional mineral fertilizers. These findings support the potential of bio-based foliar fertilization as a sustainable nutrient management approach for spring wheat production in semi-arid environments.