ISSN 1392-3196 / e-ISSN 2335-8947
Zemdirbyste-Agriculture, vol. 107, No. 1 (2020), p. 11–16
The content of mineral nitrogen in Histosols and its relationship with soil organic matter
Gediminas STAUGAITIS, Andrius ŠARKA
The aim of the research was to investigate the content of mineral nitrogen (Nmin) at the 0–30, 30–60 and 60–90 cm layers of Histosols and their relationship with soil organic matter (SOM). The experiment was conducted in natural or cultivated perennial meadows of Lithuania in 2016–2018. Every year in November, 21 sites were installed and Nmin was analysed. The studies showed that the content of Nmin in Histosols were significantly higher compared to those in mineral soils, and they widely ranged in the air-dried soil samples at different depths as follows: 37.5 to 128.2 mg kg-1 at 0–30 cm, 22.9 to 143.4 mg kg-1 at 30–60 cm and 5.2 to 85.3 mg kg-1 at 60–90 cm. Nmin content at the 0–30 and 30–60 cm layers were lower in Bathiterric Histosol and Bathifibric-Fibric Histosol compared to those in Pachiterric Histosol and Pachiterri-Fibric Histosol. In addition, the content of Nmin in Histosols depended on the peat layer thickness. At the 60–90 cm layer of Pachiterric Histosol and Pachiterri-Fibric Histosol, mineral soil was already present in many of the profiles, and SOM was lower, therefore, Nmin content was lower as well. The content of Nmin (y, mg kg-1) in Histosols was strongly dependent on the content of SOM in the soil (x, %). This dependence at the 0–30 cm layer is expressed by the equations: y = ̶ 0.02x2 + 2.72x ̶ 6.41 (r = 0.87*), at 30– 60 cm layer – y = ̶ 0.01x2 + 2.2x + 0.31 (r = 0.87*), and at 60–90 cm layer – y = 0.78x + 7.82 (r = 0.92**). At the 0–30 cm Histosols layer, the average ratio of carbon-to-nitrogen (C:N) was 18, and a very strong correlation was obtained between the ratio of C:N and Nmin content. At the 30–60 cm layer the ratio of C:N averaged 27, resulting in a weak correlation, leading to a higher impact of SOM concentration on Nmin content. At the 60–90 cm layer, in the shallow peat soils mineral horizon dominated, resulting in a high variation of the ratio of C:N from 4 to 34 and there was no correlation between the ratio of C:N and Nmin content.
Key words: Histosols, mineral nitrogen, soil organic carbon.
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