Microbiological Indicators of a Clayey Soil Planted with Wheat (Triticum aestivum L.) as Affected by Potassium Fertilization and Different Water Regimes

Abstract

A greenhouse trial was carried out in Department of Soil and Water Sciences, Faculty of Agriculture, Benha University, Egypt from November 2012 to May 2013 to determine the effect of different potassium rates and water regimes on soil microbial properties in a clayey soil. The experiment was factorial with twelve treatments (4 potassium rates×3 water regimes) in triplicates. Three soil microbial indicators were evaluated, microbial biomass (carbon and nitrogen), microbial population (bacteria and fungi) and enzyme activities (urease, phosphatase, catalase and dehyrdogenase). Moreover, the cumulative CO2 was chosen as a microbial indicator and estimated during an incubation experiment for 120 days under natural temperature. Soil microbial properties were determined four times during the experimental work. Significant increases in soil microbial biomass, microbial population and enzyme activities were recorded after addition of potassium fertilizer and these improvements became generally more noticeable with the increase of potassium applied rates. Changes of soil moisture contents caused marked effects on soil microbial biomass, microbial population and enzyme activities. Cumulative CO2 was also affected by potassium and soil water rates and its highest values were found after 120 days of incubation. Both soil water levels and potassium fertilization rates should be considered as good factors in governing soil biological properties in clayey soils.