Effect of the time and method of application of winter rye straw and compensating nitrogen on yield of spring crops and fertility indicators of sod-podzolic soil

The study investigated the impact of timelines and methods of incorporation of winter rye straw and compensatory nitrogen doses on oat and barley yields as well as main soil cultivation practices on soil fertility parameters. Under harsh drought conditions in 2023, straw application led to higher oat yields (2.38 t/ha vs. 2.14 t/ha without straw). However, nitrogen had a negative effect. Lower oat yields were observed when primary soil preparation occurred later in October compared to August and May. The positive impact of straw on crop rotation efficiency was evident—with straw, total output reached 6.12 tons equivalent per hectare versus 5.80 tons without it. Nitrogen supplementation increased barley yields by 6.9% and 7.4% only under specific straw application schedules (October and May). On fields without straw, nitrogen addition showed no significant benefits. Additionally, within crop rotations where both straw and nitrogen were applied in August, a combination treatment (ploughing for oats followed by disc harrowing for barley) yielded maximum outputs (6.95 tons equivalent per hectare) compared to conventional ploughing and zero-till treatments (6.42 and 6.16 tons respectively). Late fall processing reduced oat yields due to enhanced cellulase activity in soils. When straw was incorporated into shallower layers (0–10 cm depth) during late fall or early spring, there was a reduction in NO₃⁻ and P₂O₅ levels while NH₄⁺ and K₂O contents rose.