ASSESSMENT OF THE CHARACTERISTICS OF THE HEAVY CLAY SOILS UNDER VARIOUS MANAGEMENT SYSTEMS

Abstract

The main objective of this research work is to recognize and assess the impact of various management systems on the main features of the Vertisols in Egypt.

The Vertisols are characterized by brownish black colour, clayey texture, mostly blocky structure. In the subsurface layer, the angular and subangular blocky with shinny faces and slickensides are very clear. The gilgai features appear on soil surfaces of some profiles. Also the surface cracking are observed in the sites which cultivated with sugar cane and citrus.

The organic matter content are generally low. Some profiles under citrus and intercropping contain relatively considerable amounts of carbonates and mostly free of salinity. These Vertisols are classified into the subgroups of Typic Haplosterts, Typic Haplotorrerts and Typic Calcitorrerts. The surface layers are characterized by high contents of total nitrogen in most crop rotations. All the analysed soil samples have adequate content of available phosphorus regardless of crop type. Most of the profiles under consideration have medium to poor content of available potassium.The Vertisols under investigation, contain relatively high content of amorphous iron and manganese oxides. The cropping systems have no distinct role on the content of these oxides.

The obtained results show that bulk density to increase by depth in most profiles. The lowest values of bulk density are observed in the profile of sugar cane, while the highest figures are found in the profiles under intercropping and citrus.

The high values of penetration resistance are in citrus site while the lowest values are in the soil under cotton. There is a positive significant relationship between penetration resistance and total water stable aggregates.