Evaluation of crusting aptitude on sieved soil. A new apparatus.

The problem of crusting and surface sealing of certain soils has always presented a problem for growers of annual crops from seed because seedlings, if they emerge at all, can do so only through cracks in the crust. Formation of a crust soon after a crop is sown may allow only few seeds to emerge so that the crop has to be replanted. Crops particularly sensitive are small seeded grasses [23] and vegetables as carrot [32], onion [33] and also bean [27] and sugarbeet [12]. Interest in the topic as a research objective arose following the studies by Richards [26] which used the modulus of rupture technique to define the critical crust strength of artificial crusts. Crusting is a complex process [3, 9] resulting above all from the action of some meteorological conditions on soils in which fine and rough silt prevail, with low clay and organic matter content 1 [13]; sandy soils can also be subjected to crusting.