YIELD OF TRADITIONAL CROPS IN THE POLISSIA REGION IS INFLUENCED BY THE DYNAMICS OF EXCHANGE ACIDITY IN SODPODZOLIC SOIL OVER TIME, DEPENDING ON VARYING RATES OF CaCO3 APPLICATION

Abstract

In Ukraine, approximately 10.3 million hectares (26.3% of total arable land) are classified as acidic soils. In the Rivne region, 32.6% of total arable land is classified as acidic, ranging from very strongly acidic (9%) to slightly acidic (12%). The objective of this study is to analyze the duration of the effect of different lime rates on the dynamics of soil exchange acidity and crop response to corresponding shifts in pH levels. An eight-year field experiment investigated the impact of varying lime (CaCO3) application rates on soil acidity (pH) and crop yields in sod-podzolic soil. Mineral fertilizers (ammonium nitrate, granulated superphosphate, and potassium chloride) were applied under each crop in the rotation according to the experimental scheme. Cattle manure was applied to potatoes (50 t ha⁻¹) and fodder beet (80 t ha⁻¹). The crop rotation area saturation was 16 t ha⁻¹ of manure and N55P68K75 of mineral fertilizer. Crop yields were determined by separate-plot weighing. Before starting the experiment, chemical amelioration was carried out with lime (83.7–92.1% CaCO3). The physical application rate of lime was calculated based on the soil’s hydrolytic acidity (Hh). The following lime doses (t ha⁻¹) were applied: 0.5 Hh CaCO3 (1.8 t ha⁻¹); 1.0 Hh CaCO3 (3.6 t ha⁻¹); 1.5 Hh CaCO3 (5.5 t ha⁻¹); 2.0 Hh CaCO3 (7.0 t ha⁻¹). Lime application rates (0.5–2.0 Hh CaCO3, equivalent to 1.8–7.0 t ha⁻¹) significantly increased soil pH from an initial range of 4.6–4.8 to a final range of 6.1–7.6 within the first three years. However, soil pH exhibited a tendency to re-acidify by the experiment’s end, with final values ranging from 4.9 to 6.5. Crop responses to liming varied considerably. Potato yield remained unaffected within the tested pH range (4.4–7.4), while vetch-oat green mass (pH 5.7), winter rye (pH 5.8), flax (pH 5.6), fodder beet (pH 7.3), spring barley (pH 5.3), meadow clover (pH 5.9), and winter wheat (pH 6.3) achieved their highest yields under these optimized pH conditions. Compared to control plots, crop yield increases ranged from 0% to 120% across the studied crops under different liming rates. The most substantial yield increases were observed for fodder beet (120%) and winter wheat (42%). These results underscore the importance of considering cropspecific pH optima and tailoring liming rates accordingly. Optimizing soil pH to match crop requirements can lead to substantial yield enhancements for various agricultural crops.