Abstract
Nworie River watershed in Owerri Imo State, Southeast Nigeria is an Urban watershed that should provide agricultural resources to the inhabitants of the area; however, the watershed has been under ecological threat as result of some activities of people within the area leading to soil degradation in the form of gully erosion. The study area was divided into Upstream, Midstream and downstream after which Five Major gullies were used for the study. Soil samples were collected from the walls of the gullies beginning from down to up according to apparent horizon differentiation. Soil profile pit was dug 100m away from erosion prone area and this served as the control. Soil data collected were subjected to statistical analysis; Variation of soil properties at various sampling points were ranked according to standard procedures. Soils of the watershed were found to be acidic. The results of some physical soil properties for soil quality evaluation were matched with FAO standard to assess the degree of degradation. Soil texture of the watershed was sandy and can be classified as an Ultisol. The watershed had low variation of SCR with mean values of 0.20,0.10 and 0.26 obtained respectively at the upstream, midstream and downstream. Bulk density was high and ranged from 1.81g/cm3 to 2.22g/cm3 at the Upstream,1.78g/cm3 to 2.71g/cm3 at the Midstream and 2.22 g/cm3 to 2.36g/cm3 at the downstream indicating moderately to highly degraded. Bulk density significantly and positively correlated with sand at P=0.01 respectively at the Upstream and Midstream. The mean values of moisture content of the watershed at the upstream, midstream and downstream were 1.02%,0.69% and 3.62%. Hydraulic conductivity of the soil ranged from 2.65cm/hr to 8.12cm/hr Upstream, 0.90cm/hr to 8.20cm/hr Midstream and 2.68cm/hr to 3.25cm/hr downstream indicating moderately slow to moderately rapid soil. Aggregate stability of the watershed was low with mean values of 0.32 ,0.38 ,0.40 at upstream, midstream and downstream respectively. Erosion within the watershed was more pronounced at the upstream and midstream compared to the downstream hence the need for appropriate conservation measures and practices within the watershed is paramount.
Highlights
IntroductionLand degradation is an integral part of environmental change which leads to loss of valuable resources
The watershed is covered by depleted rainforest vegetation; grasses and broad leaf weeds like Panicum Maximum (Guinea grasss), Pennisetum Purperum (Elephant grass),Axonopus Compressus(Carpet grass), Elusine Indica(Goose grass), Centrosema Pubescens, Calapagonium Mucunoides,Aspillia Africana,Andropogon Gayanus(Gamba grass)as well as few forest species e.g palm trees, mango trees, cashew tree dominated the vegetation of the watershed
Grade of soil structure in the watershed indicates that structureless to weak soil structures predominates in the degraded area while moderate to strong structure dominated the undegraded area
Summary
Land degradation is an integral part of environmental change which leads to loss of valuable resources. It represents a downward trend in the environmental resource such that their level of use in human society decreases at an increasing rate (FAO, 1994). Land degradation is one of the leading critical environmental issues facing Nigeria. It is of varying types and the degrees are generally un-evenly distributed ranging from less devastating such as sheet erosion and mild gullies to highly dangerous ones such as loss of soil bio-physical characteristics
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