Improving levels of organic matter in desert soils is necessary for their cultivation. A two-year study (2008 to 2010) was conducted on a sandy clay loam soil at the experimental research farm of the Omdurman Islamic University, Sudan to determine the effect of application of crop residue, sewage sludge, and humentos on selected soil properties in wheat-guar crop rotation system. Treatments were recommended inorganic fertilizer (125 kg N ha−1 and 92 kg P ha−1), recommended inorganic fertilizer with crop residues, crop residue, sewage sludge (10 t ha−1), humentos soil conditioner (200 L ha−1), and control.
Results showed that soil physical properties were not significantly changed except soil water holding capacity. Application of crop residues with recommended fertilizer and sewage sludge for three seasons significantly increased cation exchange capacity and organic carbon by 57.15 % to 60.95 % and 61.0 % to 65.2 %, respectively. Moreover, combined application of crop residues with recommended inorganic fertilizer and sewage sludge had significantly decreased topsoil pH.
The results showed that judicious combined application of organic wastes with inorganic fertilizers could be a useful practice in sustaining fertility of poor sandy soils.