CHANGES IN SOIL POROSITY IN REMOLDED SOILS TREATED WITH POULTRY MANURE

Abstract

We studied the modification induced in soil porosity, pore shape, and pore-size distribution in three soils of different textures treated with a poultry manure in laboratory trials, and we tested the effect of wetting and drying cycles. Porosity measurements were carried out on soil thin sections by using the electrooptical image-analysis (Quantimet 720) technique. In all samples treated with the poultry manure, soil porosity was always higher than in the control samples. The application of wetting and drying cycles first increased the soil porosity in all samples, particularly in treated samples, to a maximum, and then porosity decreased steadily with further wetting and drying cycles. Modifications in pore size and shape were also observed. Pores ranging from 30–500 μm, which are considered of agronomic importance, were more numerous in the treated samples than in the control ones, and, particularly, the proportion of elongated pores in this range was higher in the treated samples. Also the proportion of pores larger than 500 μm was higher in the treated samples than in the control ones, and the elongated pores represented the highest part of this proportion. Consequently, the addition of organic materials, such as poultry manure, to the soil seemed to improve the porosity of the soils.