Soil Ammonification Activity in the Conditions of Mineral and Organic Fertilizer Use

Abstract

Two-year investigations (1996-1997) were carried out to examine the effect of different N rates (N1-30 kg/ha, N2-60 kg/ha and N3-90 kg/ha), standard P and K amounts (75 kg/ha) and organic fertilizers (solid manure–45 t/ha and liquid manure–80 t/ha) on the microbiological activity of the smonitza soil under spring oats. The trial was set up on the Faculty of Agronomy Experimental Field in Cacak in a randomized block design with three replications. The effect of the applied fertilizers on soil microorganisms had been determined twice during the growing season and observed by establishing the number of ammonifiers and the soil proteinase activity using standard microbiological and biochemical methods. The investigations showed that the applied fertilization variants, sampling periods and study years had affected the number of microorganisms and the soil proteinase activity. Mineral fertilizers had caused a reduction in the number of ammonifiers. The N3 variant had the highest inhibitory effect of all the variants of the mineral fertilizers studied. The inhibitory effect of the fertilizers used was more pronounced in the second sampling period. As opposed to that, the same fertilizers increased the soil proteinase activity, particularly in the first sampling period. Furthermore, the organic fertilizers used caused a reduction in the number of ammonifiers and proteinase activity. The number of ammonifiers was bigger in 1996 and the soil proteinase activity was reported to be higher during 1997.