JN Nwite, CN Mbah, CI Okonkwo,
Abstract
A field experiment was conducted in 2006 and 2007 cropping seasons to analyse the physical conditions of an Ultisol contaminated with spent lubricant oil alone, contaminated with spent lubricant oil and amended with organic wastes and organic waste amended soil only. The residual effect of these treatments was evaluated in 2008 cropping season. The treatments include; Spent lubricant oil (OS), OS+ burnt rice mill waste (OSBW), OS+ unburnt rice mill waste (OSUB), OS+ saw dust (OSSD), burnt rice mill waste (BW), unburnt rice mill waste (UBW) and saw dust (SD). A control (without oil or wastes) was also included. Results from the study showed that OS recorded significantly (p<0.05) higher bulk density (Bd) values compared to OSSD, OSBW,OSUB, BW, UBW, SD and C in the two cropping seasons of application. Results also showed that amendment of the soil with SD, BW and UB recorded higher values of total porosity (Tp), aggregate stability (As), hydraulic conductivity (Hc) and available water capacity (AWC) compared to OS, OSSD and OSBW in 2006 and 2007 cropping seasons. Amendment of soil with BW was observed to increase AS by 17%, 4%, 2%, 21%, 5%, 9% and 11% for C, UB, SD, OS, OSBW, OSUB and OSSD, respectively in 2007 cropping season. In the residual cropping season, improvement in AWC and HC were in the order BW>OSBW>UB>SD=OSSD=C=OSUB>OS and BW> UB>SD>C>OSBW>OSUB>OSSD>OS, respectively. Organic wastes were observed to improve soil physical conditions with highest improvement observed in BW amendment.