Title: The effects of lime on pH values of soil at different pH levels

Abstract

An experiment on nitrogen fertilization (60-240 kg N/ha) was carried out for 42 years (1964-2005) at Sámsstaðir in Southern Iceland. Application of N during this period resulted in a decrease of soil pH, especially in plots that received high doses of nitrogen. These plots with variable pH values were used for a new experiment with different types and amounts of lime application, implemented in 2008. It included four treatments on each nitrogen plot: zero lime, 2 and 4 tons of lime with 35% Ca and 1.4% Mg and 4 tons of lime with 20% Ca and 12% Mg. Soil samples were collected in 2012. It was revealed that soil pH had increased in non-limed plots, especially in the most acid plots (240 N). In 7 years it increased by 0.44-0.86 pH units, probably due to the intense mineralization process in the soil. Additionally, liming application increased soil pH significantly at 0-5 cm soil depth (p<0.001). The pH increased linearly by 0.1 pH unit for each ton of lime applied and the lime effects were similar in all nitrogen plots. Only a very little effect of liming could be found at a 5-10 cm depth.