Influence of fertilization and tillage systems on the humus condition of dark-grey podzolic soil

Topicality. Modern agricultural systems have an ambiguous effect on the humus condition of soils. The urgent task is to restore and preserve the fertility of the dark grey podzolic soil and increase the organic matter content in the agricultural system. Purpose. To determine changes in the humus condition of dark grey podzolic soil under sunflower under different tillage and fertilisation systems using crop rotation by-products. Materials and methods. In the long-term stationary experiment, the following tillage systems were used: ploughing at a depth of 25–27 cm, disking at 15–17 cm and disking at 10–12 cm. Ploughing under sunflower was carried out with plough PLN-3-35, disking – disc harrow AG-2.4-20. The fertilisation systems were as follows: 1) no by-products; 2) by-products; 3) N10 (ammonium nitrate) per 1 tonne of by-products. The humus content in the soil was determined according to the I.V. Tyurin’s method, the group composition of humus – according to method of M. M. Kononova and N. P. Bielchikova. Results. It was established that the highest humus content in the 0–20 cm layer of the soil under sunflower was 2.09 % for the variant with disking at a depth of 15–17 cm using by-products. On dark grey podzolic soil, humus accumulation is enhanced by disking at 15–17 cm and fertilisation with by-products and N10, which is accompanied by characteristic changes such as an increase in the total content of humic acids and non-hydrolysed residue in the humus group composition. The highest content of humic acids was 0.29–0.34 % in the plots with moldboardless tillage under different fertilisation systems. The lowest content of this important humus fraction was 0.23–0.25 % in the variant with different depth ploughing. In the variants with disking to a depth of 15–17 cm and 10–12 cm when using by-products with N10, the highest values of the ratio between carbon in humic acids and carbon in fulvic acids were 1.26 and 1.27, respectively. Conclusions. Application of moldboardless tillage, disking at a depth of 15–17 cm and fertilisation system with by-products + N10 contribute to the recovery of dark grey podzolic soil fertility and improvement of its humus condition. In Western Polissia of Ukraine, it is recommended to carry out disking at a depth of 15–17 cm with the use N10 per 1 ton of by-products in the fertilisation system for sunflower cultivation. Key words: humus, dark grey podzolic soil, fertilization system, humic acids, fulvic acids