Effect of the application of salmon sludge on the structural quality of an Ultisol

Abstract

The application of salmonicola sludge in agriculture allow to improve soil fertility, due to its high content of organic matter and nutrients available. However, there is no clarity about the effect of sludge application on soil physical properties. The objective of this investigation was to determine the effect of the application of salmon sludge on quantitative parameters and functional aspects of the porous system of a soil. Disturbed and undisturbed soil samples were collected from Los Ulmos Series (Typic Paleudults) and different doses of sludge were applied (0, 40 and 80 Mg ha-1). Six wetting and drying cycles were performed with samples assembled with the different sludge applications. In each cycle the air permeability (Ka) and the volumetric changes of the samples were measured. Subsequently, the contact angle and the stability of aggregates were determined. High doses of sludge applied to the soil generate a substitution of macroporosity for pores of water that can be used by plants, decreasing the wCP (or air capacity) by 46% and increasing the PAW by 14%, which produces an increase in structural stability and resistance to wetting. The air permeability was not affected by the dose of sludge. The recycling of salmon sludge is presented as a viable alternative to be used on degraded soils, but it is undoubtedly necessary to carry out further studies to evaluate the effect of successive doses on the soil regarding e.g. the increase in water repellency.