The effect of sewage sludge on and cup plant’s (Silphium perfoliatum L.) biomass productivity under Western Lithuania’s retisol

Abstract

The long-term field experiment with new high yielding perennial energy crop - cup plant (Silphium perfoliatum L.) was conducted in order to evaluate its biomass productivity in Vėžaičiai branch of the Lithuanian Research Centre for Agricultural and Forestry. Experimental site – naturally acid Bathygleic Dystric Glossic Retisol, pH 4.2-4.4. Granulated sewage sludge was applied (at 45 and 90 t ha-1 rates) as an alternative organic fertilizer. The fertilization was done at the beginning of the experiment, prior to cup plant’s sprouts planting in 2013. Each experimental year, traditional N60P60K60 fertilization was performed in a separate treatment. Cup plant’s biomass was harvesting once per season at the end of vegetation. Cup plant’s dry mass (DM) yield substantially increased from 2.80 t ha-1 (in 2014) to 13.41 t ha-1 (in 2016). The use of sewage sludge fertilization was notably superior to that of mineral fertilization for cup plant’s biomass productivity. In all experimental years, the optimal was the application of 45 t ha-1 rate of sewage sludge - in compare with unfertilized treatment (control), DM yield increased by 66 %, on average. Increasing of sewage sludge rate up to 90 kg ha-1 did not give any DM yield supplement. Energy evaluation of growing technology revealed that the application of 45 t ha-1 sewage sludge rate caused the substantial increase of energy output from 1 ha; and on the contrarily, sharply decreased net energy ratio. In order to determine the long-term effects of fertilization on biomass yield, these studies will continue a few more years.