The aim of this research was to compare effects of fertilization with various ratios of N, P and K (N:P:K) on arbuscular mycorrhizal fungi (AMF) infection in roots of Dactylis glomerata in Ca-carbonate (limed) and non-limed meadow plots at the Research Centre of Skriveri, Latvia University of Agriculture. Dactylis glomerata roots were excavated from variously fertilizer plots, a minimum 3 root samples per plot and analysed for two consecutive years. Arbuscular mycorrhizal fungi infection rates were estimated according to accepted scoring tables used for determination of AMF colonization.

Liming soils make both direct and indirect effects on greenhouse gas (GHG) emissions. If raising the pH of soil, the amount of N2 O emissions in the result of nitrification decreases; therefore, it is important to perform also maintenance liming if applying nitrogen fertilisers. Liming acidic soils contributes to the absorption of nutrients supplied by means of fertilisers by plants, limits the spread of plant diseases, forms better soil moisture and air regimes for plants, improves the structure of soil and activates microorganisms. The aim of this study was to assess liming effect on nitrogen use efficiency and nitrogen oxide emissions in crop farming. To achieve the aim, this study proceeds in two stages: 1) to analyse the scientific literature on the liming effect on nitrogen use efficiency and nitrogen oxide emissions in other countries, as a few such research studies are available in Latvia; 2) to calculate potential gains and losses from liming acid soils in order to examine the real situation concerning liming and its effects on the economy of farms. The research finds out that at the farm level in Latvia liming gives a positive economic effect (41.6 EUR haE-1) however, it is essential for maintaining soil fertility, increasing yields, and presumably for more efficient circulation of nitrogen, which decreases nitric oxide emissions.