Organic Matter and Physical Properties of Crude Oil Contaminated Soil Amended With Termite Soil and Blue Porter Plant

Abstract

Crude oil contamination in the Niger Delta has become a serious problem for soil health and agricultural production. We hypothesized that applying Trinervitermes spp of termite soil and introducing the Blue porter plant (Stachytarpheta jamaicensis) to crude oil contaminated soil can accelerate microbial activities and improve the soil's physical properties and organic matter content. A field experiment was carried out on a 0.02 ha land to assess the effects of Trinervitermes geminatus termite soil and Stachytarpheta jamaicensis plant on the physical properties of a sandy loam soil contaminated with crude oil in the Niger Delta of Nigeria. The experiment was arranged in a Randomized Complete Block Design (RCBD), consisting of 13 treatments in 3 replications. The soil was contaminated with 4% crude oil (equivalent of 40,000 mg kg-1) (Cr4) and 5% crude oil (equivalent of 50,000 mg kg-1) (Cr5), in single application. The soil was treated with 10 and 20 t ha-1 of Trinervitermes geminatus termite soil (10Mo and 20Mo, respectively), alone and in combination with Blue porter plant (Stachytarpheta jamaicensis). Results revealed that 6-month applications of Trinervitermes geminatus termite soil and Stachytarpheta jamaicensis plant have significant effects on physical properties and Soil Organic Matter SOM) Applying 10 and 20 t ha-1 of termite soil in combination with Stachytarpheta jamaicensis plant to 4% crude oil increased SOM from 29 g kg-1 in the control plots to about 61 g kg-1 after 6 months. The application of 20 t ha-1 termite soil to 4% crude oil (Cr4+20Mo) reduced soil bulk density, increased saturation water content by 15%, and saturated hydraulic conductivity (Ksat) from zero to 1.67 and 1.53 cm h-1 in 6 months, after the application compared to the untreated Cr4 soil. Macro-aggregates > 0.25 mm were generally higher in the termite soil alone and in combination with the Blue porter plant. Micro-aggregates <0.25 mm dominated the Control plot (54 and 46% after 3 and6 months). Water stable aggregates in 4.75-2.0 mm size class increased from 22% to 56% for Cr5+20mo after 6 months. The termite soil improved the macro-aggregates, while the Blue porter plants improved Ksat of the soil after 6 months.