Influence of wastewater sludge application on soil chemical properties in Miscanthus x giganteus

Proces obrade otpadnih voda i zbrinjavanje nusprodukata (mulj), predstavlja aktualan problem u svijetu. U današnje vrijeme primjena mulja na poljoprivrednim površinama jedna je od važnih alternativa za odlaganje. Mogućnosti primjene mulja ovise o njegovim fizikalnim i kemijskim svojstvima, a oni u značajno mjeri ovise o provedenim tehnološkim postupcima pročišćavanja otpadne vode i obradi mulja. Budući da je bogat organskim i anorganskim biljnim hranjivim tvarima, mulj može zamijeniti gnojivo, ali dostupnost potencijalno otrovnih metala često ograničava njegovu upotrebu. Cilj ovog rada je utvrditi kemijska svojstva mulja i kemijska svojstva tla prije i nakon primjene različitih količina mulja. Pokus je postavljen po shemi split plot sa 4 gnojidbena tretmana u 4 ponavljanja: T1= 0 t/ha ST (bez gnojidbe), T2= 1,66 t/ha ST mulja, T3= 3,32 t/ha ST mulja i T4= 6,64 t/ha ST mulja. Na tretmanima s mulje, u oraničnom sloju (0-30 cm) utvrđen je veći sadržaj humusa, nitrata i amonijaka, a ovisno o tretmanu, utvrđen je i veći sadržaj kalija i magnezija. Također, primjena mulja statistički značajno je povećala u oraničnom sloju (0-30 cm) količinu kadmija (1,008 mg/kg), kobalta (21,1 mg/kg) i nitrata (1,24 mg/100g). U oraničnom sloju utvrđene su i veće koncetracije cinka, bakra, željeza, olova, nikla i mangana. Primjenom mulja, u podoraničnom sloju (30-60 cm) utvrđen je veći sadržaj nitrata, amonijaka i kalija, a u tretmanu s 1,66 t/ha ST mulja utvrđen je veći sadržaj humusa. Nadalje, u podoraničnom sloju utvrđena je veća količina cinka, bakra, željeza, olova, kroma, kadmija i kobalta.The process of wastewater treatment and disposal of by-products (sludge) is a current problem in the world. Nowadays, the application of sludge on agricultural land is one of the important alternatives for disposal. The possibilities of application of sludge depend on its physical and chemical properties, and they significantly depend on the implemented technological procedures of wastewater treatment and sludge treatment. Because it is rich in organic and inorganic plant nutrients, sludge can replace fertilizer, but the availability of potentially toxic metals often limits its use. The aim of this study is to determine the chemical properties of sludge and the chemical properties of the soil before and after the application of different amounts of sludge. The experiment was set up according to the split plot scheme with 4 fertilization treatments in 4 replications: T1 = 0 t/ha dry matter (without fertilization), T2 = 1.66 t/ha dry matter of sewage sludge, T3 = 3.32 t/ha dry matter of sewage sludge and T4 = 6.64 t/ha dry matter of sewage sludge. On treatments with sludge, a higher content of humus, nitrate and ammonia was found in the arable layer (0-30 cm), and depending on the treatment, a higher content of potassium and magnesium was also found. Also, the application of sludge statistically significantly increased the amount of cadmium (1,008 mg / kg), cobalt (21.1 mg / kg) and nitrate (1,24 mg/100 g) in the arable layer (0-30 cm). Higher concentrations of zinc, copper, iron, lead, nickel and manganese were also found in the arable layer. By applying sludge, a higher content of nitrates, ammonia and potassium was determined in the subsoil layer (30-60 cm), and in the treatment with 1.66 t/ha dry matter of sludge, a higher content of humus was determined. Furthermore, a higher amount of zinc, copper, iron, lead, chromium, cadmium and cobalt was found in the subsoil layer