**2.2 Climate and agriculture**

The climate of the Mubi region is comprised of typical wet and dry seasons. The dry season spans for about 5–6 months (November to April), while the wet season usually starts from April or May to October each year. The average annual rainfall is usually within the ranges of 900 mm and 1050 mm depths with mean rain intensities of 18–24 mm as the highest in the region as reported by [17, 18]. The driest months are March and April when the relative humidity is about 13%. The average minimum temperature is 15.2°C in the months of December and January, while the

maximum temperature of up to 42°C is attainable in April [19]. Agricultural land use is mostly mixed farming systems involving cattle rearing and rain-fed arable farming, with few irrigation farming practices. Soil fertility is maintained using animal dung and inorganic fertilizer sources to support continuous crop production. The dominant crops cultivated in the area include maize, sorghum, rice, groundnut, and sugar cane. Sugar cane and vegetable crops are mainly grown on a few *fadama* lands under irrigation. The arable crops are usually grown as intercrops of maize/cowpea, sorghum/cowpea, or as sole crops of sorghum, cowpea, groundnut, and rice, which are sometimes grown in rotation based on economic reasons [17]. Basic conservation practices include tied ridges, contour bunds and shallow tillage using indigenous farm tools such as hoes, built terraces and stone lines, sandbag lines, and established vegetative barriers [20].

#### **2.3 Soils and erosion activities**

The soils of the Mubi region falls under the ferruginous tropical soil category based on genetic classifications, and as either lithosols, luvisols, or gleyic cambisols [17, 21]. The soils are derived from the underlying basement complex rocks, gneiss, and granites that characterize the Mandara Mountain ranges. The region's land topography is widely undulating with consequent erosion activities at varying levels of devastations [22–24]. There also exist a spatial pattern of land distributions often moderated by the annual rainfalls. The soils range from yellow through red to brown in colors. The soils have generally coarse, stony, and very shallow depths with nearly undefined profiles [25]. The soils are deeper at the foothills and thins out up the slopes with a predominantly sandy-loam and moderate to coarse soil textures. Soil reaction (pH) varies in the soils across the region but is generally slightly acidic to slightly alkaline with few incidences of low or high pH rates in some soils in the region. The soil organic matter (SOM) contents are widely moderate to low [10, 26]. Though the region has shallow soils (lithosols) with adequate drainage, it still has considerable soil fertility. However, the region's rockiness, isolated hills, slopes, and valleys have equally been responsible for the yearly colossal loss of soils and soil nutrients around the Mubi region. The relationship existing between soil erosion activities and their moderating variables is reported in **Table 1**.

The results reported in **Table 1** shows that soil bulk density, shear strength, clay content, and SOM contents reduced soil erosion progress, while soil erodability index, gully erosion channel length, depth, land slope, soil plastic limits, and surface runoff increased soil erosion activities around the Mubi region [27, 29].

Erosion activities are visibly spread across the region, particularly along the foothills of the Mandara Mountains such as the Mubi area (Mubi-North and South LGAs), where considerable studies were carried out to assess the magnitude of soil erosion. Field observation shows that sheet and gully erosion are the most commonly spread features on the gentle to moderately undulating terrains around Michika LGA, such as at Bazza, Garta, and Jeddel areas. The presence of such surface erosion features are found around Duhu-Yelwa, Gwaba, Sukur-Daurowa, and Kaya areas in Madagali LGA, and at Mayo-Bani District in the northern parts of Mubi-North LGA [9, 10, 17, 26]. Likewise, rill and gully erosion features are widely spread around the hilly areas of the Mubi area, especially at Digil, Vimtim, Muvur, and Betso in Mubi-North LGA, and as well as at Hurida, Madanya, Yewa, and Lamorde areas in Mubi-South LGA. Several other surface and channelized erosion features exist in most of the villages and/or farm locations scattered all around the Mubi regional landscape.

The notable agent responsible for spurring geologic soil erosion features is largely the regional terrain and/or topography that is periodically sharpened by rainfalls, agriculture, and other human activities in the Mubi region [19]. These


*Evaluation of Soil Erosion and Its Prediction Protocols around the Hilly Areas of Mubi Region… DOI: http://dx.doi.org/10.5772/intechopen.100477*

#### **Table 1.**

*Relationships between soil erosion and their predictor variables around the Mubi region.*

factors make the landscape even more vulnerable to soil erosion severity and the probability of local floods around the region.

According to [11], raindrop or splash erosion was observed as one of the predominant forms of erosion by water on the scantly vegetated or nearly bare soil surfaces, particularly at the onsets of rainy seasons in the region. Hence, soil erosion risks were found to be higher on cultivated than on fallowed lands. However, such sheet and splash erosion features are often obliterated by regular tillage activities that suppress their activities from being noticed compared to channel erosion in the region. Even though, the continuous cultivation of farmlands in an up and downhill pattern on the commonly moderate to steep slopes are notably responsible for the moderate to severe soil erosion incidences noticed around the Mubi region.

**Table 2** presents the prevailing soil degradation types and their causative factors. The results accounted for soil erosion as the main cause of soil degradation in the region [26]. Soil erosion such as splash, sheet, and rill features aggravate the destruction of organically enriched topsoils, while gullying activities worsen such problems by total removal of the top and sub-soils, plus their soil nutrients irreversibly. Findings in **Table 3** show that the channel lengths averaged between 107 m and 136 m long and between 114 m and 149 m in the months of April and in November, respectively.

The channel widths averaged between 7.12 m and 18.12 m wide in April, and was between 7.85 m and 15.19 m wide in the month of November in both years, while the channel depths respectively averaged between 2.03 m and 2.88 m in April, and was between 2.65 m and 3.77 m deep in November 2003/2004. Similar works by [9, 10, 26, 30] earlier reported comparable channel indices in the region. Previously, [9, 26] lamented the implication of such actions as they translate into poor soil fertility, lowered SOM, stoniness, and reduced agricultural production benefits, especially around areas along the Mandara mountain ranges in the region.


#### **Table 2.**

*Observed factors of soil degradation around the Mubi region.*


#### **Table 3.**

*Erosion channel and field characteristics at some sites in the Mubi area during 2003–2004.*
