Poultry Manure Application Enhances Hydraulic Properties and Aggregate Stability of Nigerian Soils

Farmers in the tropics usually incorporate organic manure to improve the low levels of soil organic matter. However, little attention is given to how this incorporated manure affects soil physical properties. This study assessed the hydraulic properties and aggregate stability of five Nigerian benchmark soils of varied textures under different rates of poultry manure application. The soil types were Iwo, Apomu, Egbeda, Oba, and Itagunmodi series, as well as continuously cropped land with extensively degraded soil. The soils were sampled at 0-15 cm soil depth (plough-layer) and subsequently air-dried and sieved through a 20 mm mesh. For each soil type, 0, 2.5, 5, 7.5, and 10 tons ha-1 of cured poultry manure were applied, and the experiment was replicated three times, resulting in a total of 90 samples (6 soil types x 5 manure levels x 3 replicates). The samples were arranged in completely randomized design and maintained at 75% field capacity for six weeks. At the end of week six, bulk density, aggregate stability, unsaturated soil hydraulic conductivity, sorptivity, pH, organic carbon, and total nitrogen were analyzed. Data were analyzed using analysis of variance and means were separated using Duncan's multiple range test at p≤0.05. Results revealed that the soils’ texture ranged from sandy loam, loamy sand and clay loam. Soil bulk density decreased with increased incorporation of poultry manure. Generally, unsaturated hydraulic conductivity increased with the incorporation of poultry manure across all the soil series except for Apomu and Oba series. Sorptivity and aggregate stability increased with the incorporation of poultry manure. Soil pH increased with poultry manure incorporation in Apomu, Oba, Iwo, Itagunmodi and the highly cultivated Iwo series, but reduced in Egbeda series. As expected, organic carbon and total nitrogen increased with poultry manure application. Conclusively, poultry manure improved soil hydraulic properties and soil aggregation, which has positive implications on water quality and availability, groundwater recharge, erosion control, fertilizer use efficiency, plant growth, biodiversity and sustainable soil use