Effects Of Integrated Use Of Vetiver Grass Strips And Mulch On Soil Erosion And Maize Grain Yield In Ikenne, Nigeria

ABSTRACT

Soil erosion is a major threat to sustainable agriculture in the humid tropics.

Management practices adopted to control soil erosion and improve soil quality include

mulching and the use of Vetiver Grass Strips (VGS). Integrating VGS with mulch could

be more effective in controlling soil erosion than VGS or mulching alone. However,

information on the effectiveness of combined utilisation of VGS and Vetiver Mulch

(VM) in controlling soil erosion and improving crop yield is scanty. Therefore, this

study was carried out to quantify the effects of integrating VGS and VM on soil erosion,

soil quality and maize Grain Yield (GY).

Three soil erosion control experiments were conducted on a Rhodic Kandiudult soil with

7% slope, in Ikenne, using maize as test crop. Treatments in each experiment were laid

out in a randomised complete block design with three replications. The potential of VGS

spaced at 10 m intervals (10VGS) and 6 t/ha of VM (VM6) in reducing runoff, soil and

nutrient losses was evaluated. Treatment with No Vetiver grass (NV) served as control.

Runoff and soil loss were measured. Carbon, nitrogen and phosphorus contents of

eroded sediment were determined using standard methods. In another experiment,

10VGS and VGS spaced at 20 m intervals (20VGS) were integrated with VM of 2

(VM2) and 4 (VM4) t/ha as: 10VGS+VM2, 10VGS+VM4, 20VGS+VM2 and

20VGS+VM4. The four integrated treatments and 10VGS, 20VGS, VM2, VM4, VM6 and

NV were evaluated for their effectiveness in reducing erosion. Data were collected on

soil loss and maize GY. Soil Physical Quality Index (SPQI) was estimated using the soil

management assessment framework. Also, 10VGS+VM4, 10VGS, VM6 and NV were

assessed for their effectiveness in reducing nitrate-N and phosphate-P in runoff. The

nitrate-N and phosphate-P concentrations were determined using standard methods, and

Eutrophic Quality Index (EQI) estimated. Data were analysed using descriptive statistics

and ANOVA at α0.05.

Runoff from 10VGS, VM6 and NV were 20.5±5.4, 16.9±6.7 and 30.9±2.3 mm while soil

losses were 337.5±9.9, 402.5±40.0 and 1079.0±18.3 kg/ha, respectively. Carbon,

nitrogen and phosphorus contents of eroded sediments for VM6 (12.65 g/kg, 1.25 g/kg

and 7.60 mg/kg) and NV (16.90 g/kg, 1.70 g/kg and 8.30 mg/kg) were higher than for

10VGS (11.05 g/kg, 1.15 g/kg and 7.30 mg/kg). Soil loss was lowest under

10VGS+VM4 (1.48±0.06 t/ha/yr) and highest under NV (7.49±0.94 t/ha/yr). Soil loss

increased in the order of 10VGS+VM4