EFFECT OF ASH-FLY ASH MIXTURE APPLICATION ON SOIL FERTILITY

Nowadays, it is illegal to apply ashes, fly ashes and their mixtures on arable soil in Slovakia although it is allowed in many countries. The reasons why the Slovak law prohibits using these substances in agriculture are not explicitly stated but most probably it is so because of the variable and often high content of heavy metals as well as the residual radioactivity in soil treated with such mixtures. However, ashes and fly ashes are significantly different in parameters, therefore they should be classified individually. It is irrational to ignore some positive effects of ashes and fly ashes on plants if they do not pose a threat of increased input of heavy metals and residual radioactivity into soil and, subsequently, in crops. The aim of this experiment has been to find out the effect of ash-fly ash mixture (AFAM) on some soil yielding parameters and to clarify opinions on using ashes and fly ashes in agriculture. A pot experiment was carried out in a vegetation cage located in the premises of the SAU in Nitra. Pots of the capacity of 30 kilos were filled with 24 kg of anthropogenic soil prepared by mixing two portions of Haplic Luvisol with one portion of siliceous sand. The ash-fly ash and/or NPK fertilizers were applied into the whole soil profile. The experimental design comprised 6 treatments (0, AFAM(1), NPK, NPK+ AFAM(1), NPK+ AFAM(2), NPK+ +AFAM(3)), each in four replications, as follows: 1 - control treatment, 2 - AFAM in a dose of 3 t ha(-1), 3 - NPK mineral fertilize; 4 - NPK mineral fertilizer + AFAM in a dose of 3 t ha(-1), 5 - NPK mineral fertilizer + AFAM in a dose of 30 t ha(-1), 6 - NPK mineral fertilizer + AFAM in a dose of 150 t ha(-1). The soil samples were analysed in the whole soil profile after harvest of spring barley. The ash-fly ash mixture in the basic dose of 3 t ha(-1) positively influenced several soil parameters. Statistically significant increase of both pH(KCl) and pH(H20) as well as the content of available calcium were noted. The total carbon content (C(ox)), carbon of humic substances (C(HS)), carbon of humic acids (C(HA)), carbon of fulvic acids (C(FA)) and available K also increased but not significantly. Sorption capacity (CEC)did not change. The sum of exchangeable base cations (EBC), base saturation (BS), conductivity (EC) and content of N(in) and Mg were not significantly influenced. The AFAM with NPK combination significantly decreased the bulk density of soil (BD). Addition of AFAM to mineral NPK fertilizers at the rates of 3, 30 and 150 t ha(-1), respectively, influenced positively the content of C(ox), C(HS), C(HA), Mg and the values of CEC, EBC, BS, BD, PH(H2O) and pH(KCl). This addition had a negative effect ob just two parameters: EC and content of mineral nitrogen. Application of ash-fly ash mixture alone or with NPK fertilizers improved soil parameters, which enhanced the soil productivity and its resistance against depressed fertility caused by unidirectional industrial nutrition.