The article presents the results of research aimed at determining the catchment areas that pose a risk of nitrogen pollution of the waters of the Mała Panew river. The research was carried out in 13 permanent monitoring points located on the Mała Panew. The location of the points ensured the representativeness of the water quality results for parts of the catchment area with a homogeneous type of land use. Concentrations of nitrate-nitrogen (NO3-N) and total nitrogen (TN) were determined in the samples taken. The content of (NO3-N) in the third quarter of the year and its relation to the value obtained for the first year quarter may be an indicator of the impact of agricultural activities on the quality of water in streams. In the case of agricultural catchments, the lowest concentrations of NO3-N and TN occur in the third quarter of the year and are significantly lower than in the first quarter of the year. The demonstrated seasonal variability of nitrate nitrogen concentrations in agriculturally used areas may be used to determine the type of pressure not allowing to achieve good water status in the surface water body. It was shown that the highest unit increments occurred in areas with a high proportion of forest.

The content of structural carbohydrates and lignin are important assessment criteria of the feed value of meadow plants. It is affected by many independent factors, including among others its development stage during the harvest as well as climatic conditions, especially the amount of rainfall. During the years 2014–2016, plant samples were harvested at weekly intervals, respectively five times from late April to late May. The effect of harvest date on cellulose, hemicelluloses and lignin contents was evaluated. The chemical composition of plants was varied, depending not only on harvest date but also on the year of study. Regardless of the course of meteorological conditions in subsequent growing seasons, the increase of cellulose (from 236.5 to 297.9 g∙kg–1 DM), hemicelluloses (from 159.3 to 210.8 g∙kg–1 DM), and lignin (from 31.5 to 43.1 g∙kg–1 DM) in the following dates of harvest were observed. These parameters were also positively correlated with the total rainfall from the begging of vegetation season to the date of plants sampling (R2 = 0.65, 0.12 and 0.44 for cellulose, hemicelluloses and lignin, respectively), and with the average daily air temperature in the moment of harvest (R2 = 0.66, 0.32 and 0.52 for cellulose, hemicelluloses and lignin, respectively). The cellulose and lignin content, regardless of the harvest date, were significantly higher in the first year of the study (2014), when moisture conditions for plant development were optimal.

Models describe our beliefs about how the world functions. In mathematical modelling, we translate those beliefs into the language of mathematics. Mathematical models can yield prognose on the base of applied fertiliser dose. In this work results of finding yield mathematical model according to fertiliser (nitrogen) dose for perennials (willowleaf sunflower Helianthus salicifolious, cup plant Silphium perfoliatum and Jerusalem artichoke Helianthus tuberosus) on marginal land are presented. Models were described as normalised square equations for dependence between yield and fertiliser doses. Experiments were conducted in lisymeters and vases for willowleaf sunflower and cup plant. For Jerusalem artichoke experiments were done in vases only. All experiments have been doing during two years (2018 and 2019) for different fertilisers doses (45, 90 and 135 kg N∙ha–1) in three repetitions. From simulations maximal yield could be achieved for following fertiliser doses – willowleaf sunflower 104 kg N∙ha–1, cup plant 85 kg N∙ha–1 and Jerusalem artichoke 126 kg N∙ha–1.