Reproduction of potential soil fertility and the state of the environment at the waste application from pig complexes

Abstract

The increase of the livestock and waste concentration per unit area of agricultural land determines a qualitatively different nature of the impact on the indicators of potential soil fertility and the state of the environment. Livestock breeding complexes for fattening up to 70 thousand pigs per year are located in the Polissya zone on typical sod-podzolic soils. However, large pig complexes cause an increase in the chemical load on ecosystems in waste disposal sites due to technical and organizational reasons related to the capacity of effluents per unit area. The research aimed to establish the parameters of changes in soil fertility and the ecological state of the environment in the conditions of the intensive waste load of pig complexes. It has established that the use for 25 years of low doses of the solid fraction of effluents from the Agricultural Open Joint-Stock Company «Agrocombinat Kalyta» as well as their combination with straw and green manure in the long-term stationary experiment of the National Science Center «Institute of Agriculture NAAS» caused widespread reproduction of sod-podzolic soil fertility. The highest fertility parameters were achieved by applying the solid fraction of effluents at a dose of N75, where the humus content was 0,28 % higher than control (without fertilizers) and was – 1,17 %. At the norm of the effluents solid fraction of N75, the content of mobile phosphorus in the soil increased to control 1,4 times, and at doses N300 – 3,2 times, which caused high soil phosphating. The content of mobile potassium in the soil at the application of the solid fraction of effluents at thedose of N100-200 remained low (70-75 mg/kg), which is required the additional application of potassium fertilizers at the dose K60-120. At the fertilizing of the soil with the pig effluents, the dose of their application should not exceed 200-225 kg/ha in terms of nitrogen has been established. At doses of N400 and above, there were a sharp increase in soil acidity, a decrease in the amount of absorbed bases by 1,9 times, an increase in the content of mobile phosphates by 25 times to the natural background, and contamination of groundwater with nitrates. At high effluents loads (N400), nitrogen leaching from nitrates in the soil thickness to 500 cm is increased 14,6 times compared to the control: at the control - 102 kg/ha, at the dose of excess activated sludge N225 - 657, dose N675 - 1488 kg/ha. At the intensive effluents loads, there was defined the inhibition of the development of most physiological groups of soil microorganisms, in particular, actinomycetes and ammonifiers. However, the number of denitrifying and phosphate-mobilizing microorganisms increased 13 and 4 times, respectively, at the increasing intensity of organic matter mineralization. It was significantly affected the processes of nitrate pollution and phosphating of the soil. The use of a solid fraction of livestock effluents in the dose of N75 provided crop rotation productivity at the level of 4,10 t/ha of grain units at the dose of N75 + K90 – 4,57. The highest productivity of crop rotation (5,65 t/ha) was achieved at the application of excess activated sludge at a dose of N225, while a similar indicator at the control was 2,56 t/ha. Further increase of the products doses of biological processing of livestock effluents reduced the payback per unit of fertilizer by 4-5 times and created an environmental hazard in the environment.