Changes in Physical Properties of an Ultisol as Influenced by Composted Empty Oil Palm Bunches and Chemical Fertilizer Under Water Stress Conditions

A greenhouse study was conducted at the University of Nigeria, Nsukka to evaluate and compare the effects of sole and complimentary use of composted empty oil palm bunch and chemical fertilizer for improvement of soil physical properties under water stress conditions. The experiment was a 3x3x4 factorial in a completely randomized design with three replications. It consisted of 3 factors–irrigation intervals, NPKMg compound fertilizer and composted empty oil palm fruit bunch. Water stress was imposed by observing irrigation intervals of 7days, 14days and 21days after irrigating the soil to field capacity. NPKMg fertilizer was applied at 0g, 28g, 42g per/polybag. While the composted empty fruit bunch (EFB) was applied 0g, 100g, 200g and 300g per/polybag . Results showed that every 14-day interval of irrigation significant (P<0.05) gave the lowest bulk density as well as highest total porosity, hydraulic conductivity, aggregate stability and mean weight diameter compared to 7 and 21-day intervals of irrigation. However, a non-significant increase in bulk density and significant (P<0.05) decrease in total porosity, hydraulic conductivity, aggregate stability and mean weight diameter were mostly observed with increasing rates of the chemical fertilizer. Similarly, the lowest significant bulk density as well as highest total porosity, hydraulic conductivity, aggregate stability and mean weight diameter values were observed with the highest rates of 300g compost/polybag. Also, results showed that combined application of 0g NPKMg and 300g compost under 14-day intervals of irrigation had the lowest (P>0.05) effect on bulk density but showed the highest (P<0.05) effects on total porosity, hydraulic conductivity, aggregate stability and mean weight diameter. Generally, the application of 300g compost/polybag was most effective in improving the physical properties of the ultisol under 14-day intervals of irrigation.