The paper provides a brief outline of the history of land reclamation in Poland and discusses its impact on the natural environment and plant crops, using the results of author’s studies and those conducted by other researchers. The process of land reclamation in Poland was practically stopped after 1990. Over the period 2000–2004 less than 4.0 thousand hectares of agricultural land was reclaimed yearly compared to 118 thousand ha in 1990 and 200–280 thousand ha during 1961–1976. As shown by the relevant studies, crops are higher on drained fields than on undrained grounds, also hay yields from reclaimed permanent grassland are better. Drainage enhances the water retention of mineral soils, 2–3 times reduces the surface flow of water, thus alleviating erosion and the washout of fertilisers, and reduces the flood wave. The average concentration of N-NO₃ in drainage water is higher than in rivers which receive the water from drains. The concentrations of other chemical components in drainage water and in rivers are similar or higher in rivers. Drainage of peat soils results in the mineralisation of organic components. As a consequence, peat bogs settle; in the Polish climatic conditions the rate of the process averages 3 cm per year for arable fields and 1 cm for grassland.

The study presents the results of research on the compressibility of two kinds of mixtures containing soda wastes from Inowrocławskie Zakłady Chemiczne „Soda Mątwy” S.A. and fly ashes from the heat-and-power station of the same plant. The tests were carried out in a prototype medium-size oedometer with the aim of determining the influence of compaction and saturation on the course of the consolidation process of the materials and the values of their compressibility moduli. The initial moisture content of wastes (close to optimal) was a constant, whereas the compaction index (from 0.80 to ca. 0.95) was a variable; the water conditions changed as well. An analysis of the test results made it possible to characterise the compressibility of the materials as dependent on the specified initial conditions, and to define the possibility of their utilisation in earth structures.

Stabilisation of road foundations with cement is an effective and economical technology of increasing the bearing capacity of ground roads. Cement-ground composites are applied in the construction of public roads as basic foundations for surfaces with high bearing capacities. On forest and country roads a layer of the composite can function as an independent road surface. Cement may be used to bond the subsoil or the aggregates of anthropogenic origin (coal refuse, slag, debris, etc.) contained in the foundations. In this way an improvement in the bearing capacity of the surface is obtained and the harmful chemical compounds present in the stabilised aggregate are immobilised. Monitoring the chemical pollutants leached out of surfaces and road foundations requires that univocal procedures are worked out to obtaine eluates from the samples. The paper presents an original method developed by the authors to assess the degree of heavy metals immobilisation while taking into account the rheological condition of cement-ground road composites. The procedure comprises the preparation of eluates for chemical analyses from monolithic cement-ground samples and samples damaged by mechanical loads. The leaching medium is deionised water with the pH value decreased to 4.

The research aimed at comparing the yield-forming value of various sewage sludges and at determining the extent to which plants utilised nutrients (N, P, K) from the fertilisers applied. Sewage sludge was used at two dates – in autumn and in spring. As suggested by the plant yields obtained, such fertilisation was more effective when sewage sludge was applied in autumn than in spring. The yield-forming effect was stronger for municipal sludge than for industrial sludge. Irrespective of the date of fertilisation and the species or even the part of the cultivated plant, the nitrogen content of plant biomass was highest in mineral fertiliser treatments. In the same treatments plants utilised this component to the greatest extent. The amount of nitrogen utilised by plants in sewage sludge treatments (irrespective of the fertilisation date) ranged between 21.8 and 37.3%. In such treatments the nitrogen content of plants was not higher than in those fertilised with farmyard manure. The phosphorus utilisation was low and regardless of the experimental series and kind of fertiliser ranged from 8.9 to 13.9%. A larger amount of potassium was found in the biomass of plants cultivated in the spring series. Potassium was utilised to the greatest extent in farmyard manure treatments.

The study examined the effects of mixing sewage sludges with calcium oxide or brown coal ash and composting the mixtures on the dry matter, organic matter, organic carbon and total nitrogen contents of the materials and their pH values. The parameters under study, except for pH and dry matter, had lower values for mixtures than for fresh sludges, with the effect being stronger for the addition of CaO than ash. Adding CaO resulted also in a stronger alkalisation of sludges and in greater losses of nitrogen. Composting decreased the organic matter, organic carbon and nitrogen contents both of sludges and their mixtures with CaO and ash. The fall in the rate of organic matter mineralisation in the composting process was larger for the CaO addition.

Research conducted in the years 1997–2001 was aimed to determine the effects of the chemical contamination of soil on the yield of Sida hermaphrodita and its bioaccumulation of heavy metals. The design of a pot experiment comprised eight treatments differing in the rate of heavy metals – cadmium, lead, nickel, copper and zinc – applied jointly to the soil. The vegetation period of Sida lasted 157 day on average. A toxic effect of the metals on the yield of the top parts of plants was observed from the level of 80 mg Cd, 480 mg Pb, 240 mg Ni, 320 mg Cu and 800 mg Zn per kg of soil dry matter. The reduction in the yield relative to the control ranged between 24 and 98%, depending on the treatment and the year of research. As the soil contamination increased, the heavy metal contents of the top parts gradually rose, as did the uptake of the metals up to the highest rates of pollutants at which it started to decrease. The uptake of heavy metals by Sida was greatest for zinc and smallest for copper. As indicated by the high levels of metals removed from the soil, Sida hermaphrodita Rusby may be considered a potential phytoextractor which will be useful for the reclamation of chemically contaminated soils.

Research carried out on the wet ash disposal site of the Adamów power plant in Turek assessed the growth of selected shrub species used for the biological reclamation of the disposal site. Ash rock on seventeen experimental plots was covered with a layer of sludge or bulder clay and in some variants the chemistry of the substrate was improved by additional NPK or N fertilisation. Biometrical measurements included the height of shrubs, the number and diameter of stems, and the length of the annual increments of shoots. Caragana arborescens and Hippophaë rhamnoides performed better than Cornus sanguinea: the shrubs of the two former species grew faster, produced more stems and had longer annual increments. All the shrub species under study achieved significantly higher values of biometrical characteristics on substrates enriched with a layer of boulder clay. Mineral fertilisation had an ambiguous effect on the relations between the characteristics studied.

Research carried out on the wet ash disposal site of the Adamów power plant in Turek assessed the growth of selected tree species used for the biological reclamation of the disposal site. Ash rock on seventeen experimental plots was covered with a layer of sludge or boulder clay and in some variants the chemistry of the substrate was improved by additional NPK or N fertilisation. Biometrical measurements included the height of trees, the number and diameter of stems, and the length of the annual increments of shoots. Robinia pseudoacacia and Eleagnus angustifolius performed better than Acer negundo: the trees of the two former species were higher, produced more stems of larger diameters and had longer annual increments. All the tree species under study achieved significantly higher values of biometrical characteristics on substrates enriched with a layer of boulder clay. Mineral fertilisation had an ambiguous effect on the relations between the characteristics studied.

The studies covered the Wymój, Sarąg, Łęguty and Isąg lakes with the Pasłęka river flowing through, and their drainage basins. It was found that the lakes of upper Pasłęka fall into degradability category II, i.e. they are moderately susceptible to eutrophication. Their drainage basins, having a great potential for supplying matter to the reservois, were included in basin category 4. The lakes with their drainage basins belong to the 2nd type of lake–drainage basin ecosystems in which the unfavourable basin conditions (high potential for solid matter supply) are balanced by the relatively high lake’s resistance to external impacts. In such a system the natural eutrophication of the lake is expected to proceed at a moderate rate. The upper Pasłęka lakes, however, show an accelerated rate of this process, which is mostly due to the high load of biogenic compounds supplied by the river and the intensive recreational use of the lakes.

Owing to the 0.6 ha area it covers, three nearby sulphur-salt springs and the surrounding marshy and grassland ecosystems, the „Owczary” natural reserve constitutes a relatively large halophyte habitat in the Kielce region. Investigations conducted in 2005 did not confirm, however, the presence of the plant communities which were recordedin the reserve in 1999. Almost the whole space of the reserve has been conquered by common reed whose expansion caused some halophytes to disappear and reduced the presence of others. The occurrence of only few specimens of halophytes and halobionts indicates that the present habitat conditions of the reserve are not favourable for them. The undesirable changes have mostly been due to the expansion of common reed, that caused shading (not tolerated by halophytes), and to to the desalination of the habitats by rainwater. As the reed expansion poses the gravest danger to the existence of halophytes, it should be limited. Undertaking activities aimed at increasing the habitat moisture by using salty waters flowing from the spring would also be recommended.