Improving acidic sandy soil properties for plant growth with dam reservoir sediments in the face of soaring fertiliser prices

Abstract

Recent actions aimed at creating an environmentally sustainable economy, as well as very high inorganic fertiliser prices, have begun a ‘renaissance’ of alternative fertilisation. It includes utilisation of dam reservoir (DR) sediments. The aim of our study was to evaluate the agricultural value of non-toxic material to be dredged from a dam reservoir in the face of changing mineral fertiliser prices. The quality of sediments was established based on pot experiment: four different sediment dosages (5 %, 10 %, 20 %, 40 %) and three plants in rotation (maize, mustard and grass mix) were tested. Application of DR sediments into sandy soil improved its texture (depending on dose 4–31 % less sand, 50–412 % more silt and 40–70 % more clay) and sorption properties, increased pH (the soil was acidic). The content of total organic carbon increased 1.4–4.3 times, total nitrogen (N) 1.4–4.7 times, ammonium nitrogen 1.3–5.2 times, nitrate nitrogen 1.7–11.8 times, total phosphorus (P) ∼1.4 times and available phosphorus ∼2.0; most changes were statistically significant. Yield of all three plants increased significantly correspondingly to the sediment application. It shows that DR sediments might be a good alternative to chemical fertilisers. Since the catchment of the analysed reservoir is mostly agricultural, N and P compounds accumulated in sediments originated from farming. Therefore, using DR sediments as fertilisers closes the cycle of these elements; N and P compounds can be used by plants. Additionally, this alternative fertiliser is cheap – since the analysed reservoir has to be dredged, large amounts of sediments will be obtained as a ‘side-effect’ of this process. Agricultural application of this nutrient-rich material would transform sediments from waste into a resource. Recent steep increase of mineral fertilisers prices – in Poland, the prices in 2022 were 2–3 times higher than in 2018 – showed that we have to diversify fertiliser sources. Low cost, ecological sustainability and good physical and chemical properties make DR sediments, if not a substitute, a good addition to the traditional methods of agricultural fertilization.