Moisture Retention Caracteristics in the Soil Formed upon Limestones and Dolomites in the Republic of Macedonia

Abstract

Th e paper presents results from the research of the infl uence of soil texture on the water retention curves of calcomelanosols, calcocambisols and terra rossa in Republic of Macedonia. Th e content of the fi ne soil separates in the calcomelanosols varies depending on the subtype. Th e physical sand fraction (coarse sand + fi ne sand) in the Amo horizon amounts to: 44.81% in the organomineral calcomelanosols, 40.13% in the organogenic and 36.52% in brownised calcomelanosols. In the (B)rz horizon in the brownised calcomelanosols it amounts to 32.64%. Th e contents (clay + silt) or physical clay in the Amo horizon amounts to: 55.19% in the organomineral calcomelanosols, 59.87% in the organogenic, and the highest content was in the brownised calcomelanosols, 63.48%. Th e average value of this fraction in the horizon (B) rz in the brownised calcomelanosols amounts to 67.36%. In the calcocambisols the average content of the physical sand fraction in the Amo horizon amounts to 33.43%, and in the cambic horizon (B)rz 22.50%. In the terra rossa the fraction physical clay is represented with a greater percentage related to the physical sand fraction. In the Amo horizon in the physical clay fraction the clay fraction is predominant, average 43.08% and 52.13% in the cambic horizon, 24.90% in Amo and 19.37% in the silt fraction. Th ere is the highest retention capacity, average 41.48% in the humus-accumulative horizon Amo in the calcomelanosols, subtype organogenic. Th e remaining subtypes of calcomelanosols have lower retention capacity in this horizon. As with retention capacity of 0.33 required in other points of tension (6.25 and 15 bar) it shows the same condition; mean value of organogenic was 29.39 and 17.22%, respectively, then organomineral 23.98 and 18.34%, respectively, and brownised calcomelanosols 21.70% and 16.60%, respectively. Th e average retention values in the Amo horizon and the cambic horizon (B)rz regarding calcocambisols amounts to 33.49% and 33.24%. Th e average retention values (pressure of 6.25 = 625 kPa and 15 bar = 1500 kPa) in the Amo horizon and the cambic horizon (B)rz regarding calcocambisols amounts to 25.27% and 17.06% respectively, and 27.89% and 16.68%, respectively. Th e average retention capacity in terra rossa, amounts to 39.05% in the Amo horizon, and 40.25% in (B)rz. Th e average retention values (pressure of 6.25 and 15 bar) in the Amo horizon and the cambic horizon (B)rz regarding terra rossa amounts to 29.92% and 20.93%, respectively, and 33.23% and 23.38%, respectively. Th e results from our research show that in Amo and (B)rz horizons there is a positive correlation between the water retention curves at 0.33; 6.25 and 15 bars and contents of physical clay (clay and silt) and clay. Also there is high negative correlation between the retention curves at 0.33 bars contents of physical sand fractions (coarse sand+fi ne sand; r = -0.47)