Concentrations of nitrogen and organic carbon in different uses of Terric Histosol

Abstract

In 2016–2019 in Eastern Lithuania, in Naujienos Terric Histosol (HSs-d), where natural and cultural meadows are grown and areas of cereal crops are annually cultivated, monitoring sites were installed. There at different times of the year at different Histosol depth – 0–30, 30–60 and 60– 90 cm layers, organic carbon (C_org.), total nitrogen (N_sum.) and mineral nitrogen (N_min) concentration and their relationship were investigated. The studies have shown that the highest N_min concentration was found in natural meadows areas, followed by cultural meadows areas, and finally cereal crops areas; in Terric Histosol at the 0–30 cm depth, mean concentrations were obtained, 100.7, 88.3 and 79.0 mg kg^–1, respectively. The highest N_min concentration was observed in the first days of July. It was 137.6 and 105.4 mg kg^–1 in natural and cultural meadows areas, respectively. In deeper Terric Histosol layers, the N_min concentration in cereal crops areas was slightly different. At the 30–60 cm depth, it ranged from 45.6 to 102.2 mg kg^–1 over the years, and at the 60–90 cm depth from 55.1 to 87.2 mg kg^–1. Nitrate formed the major part of mineral nitrogen in the studied Terric Histosol – 49.7–91.0%. C_org. concentration at the 0–30 cm depth in natural meadows areas was 41.2%, in cultural meadows areas it was 35.6% and in cereal crops areas 19.4%. The same sequence of N_sum. concentration was found – 3.04, 2.18 and 1.97%, and C:N ratio – 13.6, 16.3 and 9.8%. At deeper Terric Histosol layers the values of these indicators differed slightly between the crops areas. The N_min concentration at 0–30 and 30–60 cm depth correlated best with the C:N ratio (r_{0–30 cm} = 0.872^**, r_{30–60 cm} = 0.562^*), N_sum. concentration (r_{0–30 cm} = 0.618^*, r_{30–60 cm} = 0.568^*) and to a lesser extent with the C_org. concentration (r_{0–30 cm} = 0.341, r_{30–60 cm} = 0.564^*).