Crust formation on soils around Isfahan reduces infiltration and seedl
ing emergence in cultivated lands. Mechanism of crust formation on loc
al soils was investigated under field condition. Soil and crust sample
s from a field under furrow irrigation were taken for physical, chemic
al and micromorphological analysis. Seedling emergence of sugar beets
(Beta vulgaris) reduced by 50% due to crust forming after the first ir
rigation. Rise of water table, increase of exchangeable sodium percent
age to 6.4, and higher silt content resulted in higher susceptibility
of soil to crust formation. Crust forming inside furrows was thicker a
nd usually consisted of 3 layers as compared to a thinner crust formed
on beds with only 2 layers. Layers found in crusts of Lavark soil gen
erally had less sand and more silt and fine clay compared to the overa
ll Ap horizon. Silt and fine clay in the middle M2 layer of crust form
ing on furrows were increased from 51.6 and 5.6 to 59.8 and 21.1 perce
nt respectively. Percolation of finer particles through and inside the
pores created layers that were denser and less porous. Chemical dispe
rsion of particles together with physical deterioration of surface str
ucture by long period of mechanized agriculture in the area are probab
ly the main reasons for crust formation.