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Variability of Soil Properties in Eroded Agricultural Landscape

Wysocka-Czubaszek Agnieszka, Roj-Rojewski Sławomir

Journal of Ecological Engineering

2020

Vol. 21, nr 1

72--80

Erosion strongly influences the soil properties and affects the intra-field variation of nutrients not only in steep young morainic landscapes but also on gentle slopes of old-glacial landscapes. The aim of the study was the evaluation of changes in the plant-available nutrient contents in the complex old-glacial eroded landscape of the Bielska Plain in the north-eastern part of Poland. The soil samples were collected from the soil profiles located along the transect beginning on the flat summit of the kame hummock extending through south-facing convex slope, the toeslope and footslope and further through the north-facing uniform slope. The content of plant-available forms of phosphorus (Pdl) and potassium (Kdl) and mineral forms of nitrogen (NH4-N and NO3-N) were determined in every soil profile. The soils located in various landscape positions were characterized with different fertility. In the soil located on the toeslope the content of NO3-N, Pdl and Kdl was high, while the soil located on the summit was rich in NH4-N and poor in the plant-available forms of K and P. The erosional distribution of plant-available N, P and K enhances the variation of nutrient content within one field and contributes to high variability of crops.

Dynamics of Nitrogen Transformations in the Soil Fertilized with Digestate from Agricultural Biogas Plant

Wysocka-Czubaszek Agnieszka

Journal of Ecological Engineering

2019

Vol. 20, nr 1

108--117

The biogas production from dedicated crops creates an additional organic fertilizer which may, at least partially, substitute synthetic-N fertilizers. The digestates are characterized by an elevated NH4-N content; therefore, they may supply more readily-available N to the crops, compared to manures. Thus, the aim of the study was the analysis of N dynamics in the soil fertilized with the digestate from agricultural biogas plant fed mainly with maize silage with addition of poultry manure and potato pulp. A laboratory incubation experiment was conducted for 56 days and the soil was sampled from the field fertilized with the same digestate under the conditions of regular farming practices. In both the incubation experiment and the field study, the digestate supplied the soil in NH4-N. The inorganic-N transformation showed a similar overall pattern with some differences. In the incubation experiment, after the application of the digestate in the amount corresponding to the fertilizer dose of 170 kg N ha-1, the NH4-N content decreased rapidly during the first 14 days from 61.54±5.65 mg N kg-1 to 19.02±4.12 mg N kg-1 and then at the day 42 – to values close to zero. In contrast, the NO3-N content increased from 6.35±0.35 mg N kg-1 to 50.65±4.73 mg N kg-1 at day 14 and further to 79.06±13.95 mg N kg-1 at day 42. In the field, the elevation of the NH4-N content after digestate application was less pronounced as a consequence of lower application rate (114 kg N ha-1); however, the rapid drop in the ammonium-N content from 20.41±9.18 mg N kg-1 at day 0 to 14.80±9.75 mg N kg-1 at day 7 followed by a slow decrease until the day 56, was observed. The average soil NO3-N content was rather constant in the first 7 days after fertilization and the rapid nitrification occurred in next 49 days resulting in the nitrate-N increase to 32.97±24.46 mg N kg-1. The overall pattern of N dynamics in the soil fertilized with digestate was the same in the incubation experiment and under the field condition, even though the studied soils showed some dissimilarities. Rapid ammonium-N transformation to nitrate-N may create favourable conditions for nitrate leaching; therefore, the farm management techniques should be focused on nutrient recycling and N loss prevention.