Nigeria Gurara

Soil Survey Report

Objectives

The main objective was to identify different soil types in the Gurara River’s project area, their distribution and characteristics. Identification and characterization of the soil properties is essential for intense agricultural projects. Certain soil characteristics may limit the variety of crops, or influence decisions regarding agricultural management.


The survey is also aimed to assess the layout of the planned agricultural plots, irrigation and drainage systems, and offer recommendations concerning cultivation and irrigation management.

Project Background

The current project, the agricultural development south of the Gurara River, in the Jere village’s area, is a direct outcome of the building of a large dam on the Gurara River. The new dam has been designed in the framework of the Gurara Water Transfer Project as a multi-purpose dam to augment the supply of water to the Federal Capital Territory Abuja. The dam will allow the development of irrigated agricultural projects downstream. This project is established as a result of the new irrigation opportunities that derived from the new dam construction.


The dam and its impoundment will provide a storage volume of 700 million cubic meters. The dam capacity is sufficient to sustain future water requirements in the domestic, public and industrial sectors and will, in addition, provide a regulated discharge that can be used for electricity generation and irrigation during the dry season, taking full advantage of the reservoir’s regulating capacity. These opportunities will enhance the social and economic benefits of the Gurara Water Transfer Project.


Within this framework, the Gurara Reservoir will be connected to the Lower Usman Dam, to design and construct a project that will utilize part of the regulated flow for the irrigation of about 4,000 hectares of agricultural land.

General Description of the Project Area’s characteristics

Location


The project’s area is positioned 60 kilometers northwards from Nigeria’s capital, Abuja, and covers approximately 8,000 hectares.


Geomorphology


The area is close to the Gurara River, and has a series of ridges stretching north to the river. These ridges are defined by river channels flowing to the river. Rock exposures – usually granite, appear in the area, creating hills rising over the surface. The surface is gent and is made up of a series of moderate ridges which divide between the streams flowing to the Gurara.


Lithology


Parent material exposures appear in a number of places in the project’s area. The rocks are various types of granite and vary in shapes and appearances. It should be noted that there are no rock appearances in the depth of the soil near the rock exposures.


The drainage system


The Gurara River flows from east to west draining the project. Two, fairly large streams flow south to the Gurara River, creating a secondary division of the project’s area. These streams have a series of small tributaries connected to them creating the area’s drainage system.

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Settlements


The project’s area covers approximately – 8000 hectares. Jere, a large village of 2,000 dwellings, lies in the south–eastern part of the area. The village’s houses stretch along the main road to the north, and along the road to the east. Except for this village, there are also small village concentrations consisting of a few scattered houses. Map No. 6 shows the population’s distribution in the project’s area. The area occupied by dwellings covers about 140 hectares, approximately 1.7% of the area.

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Agricultural uses

Local Agriculture appearances

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A number of occurrences of local agriculture can be found:


a. Intensive cultivation of alluvial areas near the river Practically all of the alluvial areas along the Gurara River are cultivated. Rice, cultivated in large, orderly plots is a prominent crop. The area is irrigated by flooding since the water source is the river. In places where a levee appears over the river, vegetables, and even fruit can be found, for example mango. See picture No. 11.


b. Intensive cultivation in the west of the area The western part of the project’s area, near the village Jere, is cultivated quite intensively. The plots are small and tilled by families, approximately 0.3-0.5 Hectares. The area is not irrigated, the main crops are yam, peanuts, millet, corn, and cassava.

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In addition, an analysis of higher precision was made, showing the detailed land use distribution of the areas. This mapping was conducted in the northern part of the area, in an area of roughly 400 hectares.

Drillings

The drilling conducted by JCB were made mostly in adjacent to trails and roads. In some cases, when large areas were not accessible by any road or trail, the survey team was forced to open new roads in the forest and to locate drilling points along those trails.

FINDINGS

Soil Categories

Two dominant categories of soil types can be distinguished by their texture and color, which also coincide with the landscape units of the area.


  • Upland soils characterized by their coarse texture and variable kinds of drainage conditions are found in the higher elevated areas. The source of this soil is weathered granite rock in the area. Laterite horizons in varying degrees of hardness appear in these soils.


  • Lowland soils found in the river basin. These soils are compact and dark, have a large variety of textures, and lie along the Gurara River and its tributaries. The source of this soil is alluvial material transported by the streams from distant areas.


Cross Section


The following cross section of the project area depicts the gently undulating topography and the distribution of the soil units accordingly.

Land capability

Capability subclasses


Subclasses are groups of capability units which have the same major conservation problem such as:


E - Erosion and runoff.

D - Excess water.

C – Soil and Root-Zone limitations.


The capability subclass provides information as to the kind of conservation problem or limitations involved. The class and subclass together provide the map user information about both the degree of limitation and kind of problem involved for broad program planning, conservation need studies, and similar purposes.


Land classification for irrigation criteria in the Gurara project area


In the Gurara project the soils where classified into four major groups by their suitability for irrigation and by agricultural adequacy.


Primary division


Class 2: Arable, Moderately suitable for irrigation, adaptable to a narrower range of crops. Intermediate payment capacity.


Class 3: Arable, Marginally suitable for irrigation, deficiencies in soil, topography or drainage properties. Adequate payment capacity.


Class 4: Limited Arable/ Special Use. Suitable for very limited range of crops. Range in payment capacity


Class 6: Non arable land.

Recommendations

Summary

The soils that appear in the projects area are laterites in varying levels of development. The prominent agricultural qualities of these soils are: a low level of fertility, a rapid leaching of nutrition elements, a low water retension, and the presence of hard iron horizons in the soil’s profile and on the surface.

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The general recommendations are:


  • Addition of lime to the soil - liming, permanently, in order to improve the soil structure and the basic fertility level.

  • Addition of organic fertilizers, in order to improve the soil structure and the natural fertility.

  • Deep plowing in places in which a hard lateritic (plintite) horizon has formed.

  • Constant supervision over the levels of metal presence, especially aluminum, which can, in high amounts, become toxic to plants.

  • Follow up on the levels of nutrition elements, N.P.K, and determining the required fertilizer rations according to the area’s conditions