The Effect of Mineral Fertilizers on Soil Respiration in Urban Lawns

Abstract

Application of mineral fertilizers to regulate microbial respiration and carbon dioxide emissions from urban lawn soils was evaluated due to the need to develop technologies for reducing CO2 emissions and for increasing the C-absorption capacity of natural and anthropogenic ecosystems. The studies were performed in the Botanical Garden of Moscow State University on Leninskie 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 the doses of 60 and 120 kg N/ha during the growing season. We studied the basal respiration (BR) of soils, carbon content of microbial biomass (Cmic) by substrate-induced respiration, and the CO2 emission from soils by the method of closed static chambers. Cmic in soil of the control plot in the summer period was 1300–1450 µg/g. Application of NPKS 21 : 10 : 10 : 2 and NPK 18 : 18 : 18 + 3 MgO + TE at a low dose increased Cmic by 12–35% within the first two weeks, and then it dropped. All types of fertilizers applied for a short period of time increased BR of soils and CO2 emission maximum on the sixth day. After two weeks and onwards, their growth decreased or their intensity dropped to the control values (500 mg CO2 m2/h–1 and 1.5 μg C–CO2 g/h, respectively) and lower. The lowest intensity of CO2 emission, a rise in basal respiration, and an increase in microbial biomass were recorded after the application of fertilizer NPKS 21 : 10 : 10 : 2. The change in the functioning of the soil microbial community detected by the maximal qCO2 was the greatest in case of NPKS 27 : 6 : 6 : 2 application. The dynamics 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). Emissions of CO2 were minimal for the plot with NPKS 21 : 10 : 10 : 2 in all periods of the study.