The influence of pig manure on the humus state of quasi-gleyish agrochernozem of the southern forest-steppe of the Omsk Irtysh land

The results of studies on the influence of the solid fraction of pig manure on the humus state of quasi-gleyish agrochernozem of the southern forest-steppe of the Omsk Irtysh Land are presented. The purpose was to establish quantitative parameters of the action and residual effects of manure in doses from 20 to 60 t/ha on the indicators of the humus state of the soil. Field experiments were carried out in 2016-2019. The initial humus content in the soil was low: 2.0%. The positive effect of pig manure introduced in doses of 30-60 t/ha on the content and reserves of organic matter carbon (Соrg) of the soil was established. In the year of action of the organic fertilizer, they increased by 14.7-33.6%, over 1-2 years of residual effect by 9.2-28.6%. A strong relationship was established between the content of Corg in the soil and the dose of manure. The use of 1 t of manure increased the content of Corg by 0.007% during the period of action; in the years of residual effect it increased by 0.004-0.006%. In the composition of agrochernozem humus an increase was observed in the amount of humic acids (HA) and in the ratios Cha : Cfa from 1.64 to 2.15-2.37. The proportion of free HAs in the humic acids has increased from 73% in the option with a dose of 20 t/ha of manure and up to 97% with a dose of 60 t/ha, as well as HAs strongly connected with the mineral part of the soil (by 18-46%). The content of mobile humus substances in agrochernozem was low: 1650-1850 mgC/kg. The use of manure contributed to a significant increase in their quantity up to an average level: in the year of action by 11.8-46.5%, in the years of residual effect from 14.5-39.3 with the minimum dose of fertilizer to 27.2-56.5% with the maximum dose. The amount of energy in the soil humus was estimated as critical (996-1330 GJ/ha). The introduction of pig manure increased the energy reserves in agrochernozem up to 1190-1330 GJ/ha.