Effect of bentonite and zeolite on some characteristics of acidic sandy soil and on the biomass of a test plant

Abstract

In a pot experiment the effect of bentonite and zeolite doses [0; 5; 10; 15 and 20 g·kg soil -1 ] was studied on some chemical properties and ten soil microbiological and enzymological properties of an acidic [pH(H 2 O) = 5.65] humic sandy soil [WRB: Lamellic Arenosol (Dystric)], as well as on the biomass of perennial ryegrass ( Lolium perenne L.), as test plant. The pot experiment was set up in 2007 and 2008 at the Department of Agrochemistry and Soil Science of the Debrecen University in three replications. The average results of the two year experiment can be summarized as follows: The pH increased due to the effect of small and medium amendment doses. The bentonite treatments proved to be more effective than the zeolite doses. As the pH increased, the hydrolytic acidity – in case of the bentonite treatments significantly – decreased. Concerning the easily available nutrient content of soil, the small and medium amendment doses turned out to be effective. The large bentonite doses reduced the nitrate-N content, the easily available phosphorus and potassium contents of soil. Large dose zeolite treatments decreased the nitrate-N content, but increased both the phosphorus and potassium content of soil, in most cases significantly. Regarding the measured soil microbial parameters, the small and medium amendment doses were the most effective. The bentonite and zeolite treatments increased the biomass of perennial ryegrass, especially the small and medium doses of bentonite and the large dose of zeolite brought about significant increases. According to the statistical analyses moderate and close correlations were found between the parameters studied. In the bentonite treatments a close correlation was established between the aerobic cellulose decomposing bacteria and saccharase enzyme activity (r = 0.864) of soil. In the case of zeolite treatments, a close correlation was found between the number of nitrifying bacteria and microbial biomass C (r = 0.911) of soil.