Influence of Granulometric Composition and Organic Matter Management on Soil Stability Against Water Erosion in Southeastern Nigeria

The study investigated the influence of granulometric composition and organic matter on soil stability and eroded sediment under simulated rainfall for some soils from southeastern Nigeria. The experiment was conducted at the Glasshouse of the Department of Soil Science, University of Nigeria Nsukka (UNN). The experimental design was a 3 x 3 factorial in CRD replicated three times and involved three different soils (Nando, Abakaliki and UNN) and three poultry manure rates: 0, 20 and 40 t ha-1. Soils were measured into transparent plastic bowls, and organic treatments applied, and the entire set up left to restructure for five months. The soils were subjected to simulated rainfall at rainfall intensity of 75 mm-1. From this, the runoff was collected and measured and the mass of eroded sediment determined as a measure of soil erosion. Results showed that the water-stable aggregate fractions generally increased as the fraction size decreased. Water-stable aggregates of the organic treatments followed the order: 0.50 mm >0.1 mm >2 mm; 1 mm > 0.50 mm> 2 mm, and 0.50 mm > 2 mm > 1 mm at Nando, Abakiliki and UNN, respectively. Aggregate stability decreased in the order of: 25.1 (Abakiliki) < (Nando) < 35.3 (UNN). Increased application of organic treatments did not affect the run-off volume and sediment yield. State of aggregation (SOA), CDR and WDSi and aggregated silt + clay (ASC) significantly (p<0.05) correlated with coarse sand, while WDC, SOA, MWD and WDSi significantly (p > 0.05) correlated with Fe, Al, Mn and % organic manure.