EFFECTS OF SULLA CROP (Hedysarum coronariumL.) CONDUCTED IN DIRECT AND CONVENTIONAL DRILLINGS, ON THE PHYSICO-CHEMICAL PROPERTIES OF CLAY SOIL UNDER TUNISIAN SEMI-ARID CLIMATE

Abstract

The sulla crop (Hedysarum Coronarium L.) variety Bikra 21 was conducted in direct and conventional drillings, for treating the effects of this crop on some physicochemical properties of sloping land (6%). The experimental area is situated at Bou Salem (higher semi-arid) in the governorate of Jendouba (north-west of Tunisia). The organic sulla restitution has contributed to improve the contents of organic matter principally in layer. Indeed, the rates exceeded 3% in direct sowing as well as in the conventional one. However, the field in direct drilling was characterized by higher nitrogen contents (from 0.35 to 0.40 %). The presence of sulla improved soil structural stability (from 1.22 to 1.97 %) in direct drilling. Therefore, the cation exchange capacity was improved in layer, and was found better under the conditions of the direct drilling (from 60.2 to 65 meq/100g of soil) than in the conventional one (from 59 to 63.3 meq/100 g of soil). It should be noted that the presence of residues, especially on the surface supported the permeability of the ground, was mainly in direct drilling where the permeability was higher (17.83 cm/h in the surface of direct drilling versus 13.92 cm/h in the conventional one).