Crusting effect in the hydraulic properties of a cultivated soil

Abstract

The crusts are responsible for the reduction of water infiltration into the soil and the increase in runoff process from rains and irrigation. From infiltration test using the simple ring infiltrometer, the hydraulic properties of a soil, with and without crust, cultivated with castor bean were estimated and compared. The experiment was carried out with two treatments (with and without crust) and seven replications. The mean values of hydraulic conductivity, sorptivity, initial and final volumetric water content were compared by variance analyses computing the F ratio. The mean values of the initial volumetric and final water content between treatments were not significantly different, while those for hydraulic conductivity and sorptivity were significantly different (P < 0.01). The soils without crust were on average almost three times more conductive than the ones with crust. The averange value of the characteristic mean pore  radius (?_m) was of 0.16 mm for soils without crust and 0.19 mm with crust. Despite presenting a lower ?_m value, the surfaces without crust were more
conductive due to the density of the pores. Although the ?_m value had increased in the surfaces with crusts, the number of hydraulically active pores was approximately six times less than in the surfaces without crust.