Protection of Soil Organic Carbon (SOC) and nitrogen (N) from losses is important in evaluation and maintenance of soil fertility and environmental quality. Uncertainties exist concerning the distribution of SOC pool and N in primary particle size fractions under land use types. A study was carried out to determine the distributions of SOC and N in sand, silt and clay fractions of a sandy soil under cassava, plantain and rubber land use types in southern Nigeria. Results showed that cassava had the highest amounts of SOC in whole soil and the particle size fractions. Clay particles had significantly higher SOC across all the land use types at 0-15 cm soils (p>0.05). Total N was significantly higher in silt and clay particles of cassava and plantain soils. Coarse sands showed low amounts of SOC and total N in all the soils. Bulk densities ranged from 1.38 g cmG 3 in cassava soil to 1.5 g cmG 3 in rubber soil at the 0-15 cm depth. Total porosity was inconsistent in all the soils. Macro-aggregate fractions were more stable in cassava and plantain soils. Therefore, land use practices that lead to loss of clay and silt particles in large amount may deplete large reserve of the soil organic carbon and nitrogen.
The experiment was conducted at Teaching and Research Farm of University of Port Harcourt betweenMay and August, 2016 to determine the influence of different soil management practices on soil organisms and maize yield (Zea mays L.) in South Eastern Nigeria. The experiment consisted of six treatments, namely: control (no application), cover crop (pumpkin cover), 10 t/ha dry guinea grass mulch (dead mulch), 10 t/ha poultry manure, 250 kg/ha N:P:K 15:15:15 and 10 t/ha dry guinea grass as bush burning material. These treatments were laid out in a Randomized Complete Block Design with four replicates. Results showed that the initial bacterial count was 2.0 × 10 6 CFU/g, fungal count (1.7 × 10 5 cfu/g), and earthworm casts (0). The soil was sandy loam and the pH was very strongly acid (4.80). At 11 weeks after application (WAA), NPK treated plots had the highest bacterial count (4.6 × 10 6 CFU/g), while cover crop and dead mulch plots had the highest fungal count (1.9 × 10 5 cfu/g). At the point of harvest, the highest earth worm casts (19.00) were in cover crop. The most predominant bacteria isolates across the various soil management practices were Bacillus and Pseudomonas species, while that of fungal were Aspergillus niger and Candida species. Maize yield differed significantly (p0.05) among various soil management practices. In spite of the variation in the population of soil organisms, NPK plots produced the highest yield (170 kg/ha) and is therefore recommended.
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