THE EFFECT OF MINERAL FERTILIZERS ON SOIL RESPIRATION IN URBAN LAWNS

Abstract

Due to the need to develop technologies for reducing carbon dioxide emissions and increasing the C-absorption capacity of natural and anthropogenic ecosystems, the possibility of using mineral fertilizers to regulate microbial respiration and CO2 emissions from urban lawn soils was evaluated. The studies were carried out on the territory of the Botanical Garden of Moscow State University on the Lenin Hills in a small-plot experiment with the fractional application of four types of complex fertilizers (NPKS 27:6:6:2, NPKS 21:10:10:2, NPK 15:15:15 and NPK 18:18:18 + 3 MgO + trace elements (TE)) at doses of 60 and 120 kg N ha-1 during the growing season. The carbon content of microbial biomass (Cmic) using substrate-induced respiration was studied, the basal respiration (BR) of soils was estimated, and the emission of CO2 from soils using closed static chambers was determined. Тhe Cmic content in the soil of the control plot in the summer period varied within 1300–1450 μg·g-1. The application of NPKS 21:10:10:2 and NPK 18:18:18 + 3 MgO + TE at a low dose increased the Cmic content by 12–35% for two weeks, then it de-creased. The application of all fertilizers for a short period increased basal respiration of soils and CO2 emission, maximum on the 6th day. Aft er two weeks, the increase in the intensity of BR and CO2 emission decreased or it reached the control values (1,5 μg C-CO2·g-1·h-1 and 500 mg·CO2 ·m-2·h-1 respectively) or less. In the short term, the lowest intensity of CO2 emission and a surge in basal respiration, along with an increase in microbial biomass, were observed with the addition of fertilizer NPKS 21:10:10:2. The greatest change in the functioning of the soil microbial community, revealed by the maximum qCO2, occurred with the introduction of NPKS 27:6:6:2. Th e dy-namics of CO2 emission from the soils of the small-plot experiment from April to October correlated with the soil temperature (rS = 0.66, p<0.05, n=135). In all periods of the study, the minimum CO2 emissions were noted for the plot with NPKS 21:10:10:2 fertilizer.