The Effect of Faidherbia albida (Gawo) on Soil Fertility in Some Selected Smallholder Farms in Gwandu LGA, Kebbi State, Nigeria.

Table of Contents

ABSTRACT

Introduction

Statement of the Problem

Objectives of the Study

Materials and Methods

Design

Data Collection

Soil Laboratory Analysis

RESULT PRESENTATION

DISCUSSION

Conclusion

Recommendations

REFERENCES

>ABSTRACT

The study was carried out to assess the effect of Faidherbia albida soil fertility in some selected smallholder farms in Gwandu Local Government Area of Kebbi State, Nigeria. Ten

(10) isolated trees of Faidherbia albidaspecies grown on similar site conditions were selected at random on farmer’s farms. Radial distance based soil sampling (under the canopy, near to the canopy and outside the canopy) was adopted for the research work. Experimental design used was 1x3 arrangements of treatments (three radius) in Randomized Complete Block Design (RCBD) replicated 10 times (10 scattered trees). A total of sixty (60) composite soil samples were taken at two (2) different depths (0-15cm and 15-30cm) at three (3) distances (radius) in four (4) different directions (north, south, east and west) of each tree. The soil samples collected were analyzed for soil texture, soil reaction (pH), Cation Exchange Capacity (CEC), soil organic carbon, total nitrogen, available phosphorus, potassium calcium, magnesium and sodium to assess fertility status of the soil. The analyzed results showed soil reaction (pH) were slightly high in all the canopies under Faidherbia albida.Available phosphorus and calcium recorded low status, Cation Exchange Capacity, potassium, magnesium and sodium recorded medium status. Soil total nitrogen recorded high status under the three canopies of F. albida. In term of soil physical properties, loamy sand was observed under the mid-canopy position and sandy soil under the canopy edge and canopy gap respectively. Conclusively, an improvement of soil chemical and physical properties was observed under the canopy of F. albidatree in the study area.

Introduction

Soil nutrient degradation is considered as a major challenge in achieving food security and natural resource conservation in sub-Saharan Africa such as Nigeria (Sanchez and Swaminathan2005; Bationo et al.,2007). It is estimated that Africa loses US$4 billion per year due to soil nutrient degradation (Bationo et al.,2007). The problem is pervasive among mixed crop and livestock farming systems of the region where competing uses for crop residues such as livestock fodder or household fuel that do not sufficiently replenish the soil exist. Nutrient replacement using mineral fertilizers is a limited option for many smallholder farming households of the region. At only eight kilograms per hectare, the region has the lowest mineral fertilizer application rates in the world and concomitantly, much lower crop yields than achieved in other developing regions (Morris, et al , 2007).

Conventionally in modern agriculture, increased productivity has been achieved mainly through application of synthetic inorganic fertilizers. However, the increasing price of synthetic fertilizers and the inability of poor farmers to gain access to them pose severe constraints on their widespread use. Although organic matter may be an alternative source of nutrients, neither animal manure nor green biomass is usually found in adequate quantities to meet the high application rates (10–40 Mg ha ^–1 year⁻¹) required to meet the nutrient requirements of crops (Mafongoya, et al., 2006).

Improving fertilizer use efficiency by a combination of organic and inorganic nutrients is vital to the long-term sustainability of global agriculture. Within this important goal there is great potential for the more effective utilization of biological N-fixation (BNF), which is virtually without cost. BNF accounts for 60% of N production (Zahran, 1999) and 16% of the current global Nitrogen (N) input (Liu et al., 2010). However, in Africa and South America, BNF is the single largest Nitrogen (N) source, accounting for 32–34% of the Nitrogen (N) input (Liu et al., 2010). In this respect its further use would, at the least, ease the pressure for land through the rehabilitation of degraded areas (Herridge et al.,2008). However, BNF can also play a greater role in sustainable agriculture as it increases Nitrogen (N) recovery rates in addition to reducing the need for synthetic fertilizers.

In Southern Africa, the consequent downward spiral of soil fertility has contributed to a corresponding decline in crop yields, an increase in food insecurity, food aid and environmental degradation (Mafongoya et al., 2006). In order to mitigate nutrient mining, agroforestry or (fertilizer tree) systems have been proposed as an innovation especially suited to resource poor farming households. Fertilizer tree systems add biologically fixed nitrogen and other agriculturally important nutrients to the soils. This is done in a way that complements the crops grown in association with the trees (Akinnifesi et al.,2010a).

Statement of the Problem

Nutrients replacement using mineral fertilizers is a limited options for many smallholder farming households of the study area. This is because, increasing price of synthetic fertilizers and the inability of poor farmers to gain access to them pose severe constraints on their widespread use.

However, leguminous trees such as Faidherbia albidathat is nitrogen fixing tree is known to play a complementary or alternative role as a source of organic fertilizer and have the potential to sustain soil fertility. The contribution of is tree to soil fertility enhancement is not adequately studied in the study area. Hence, this study quantified the effects of Faidherbia albidaon soil physical and chemical properties in the study area following a radial distance gradient method from the tree trunk.

Objectives of the Study

The main objective of the study is to examine the effect of Faidherbia albida tree on soil fertility in some selected smallholder farms in Gwandu Local Government Area, Kebbi State, Nigeria.

The specific objectives are to:

1. determine the effect of Faidherbia albidaon soil physical under F. albida canopies in the study area.

2. assess soil chemical properties (Soil texture, Soil pH, SOC,CEC, TN, AVP, K, Ca, Mg and Na) under F. albida canopies in the study area.

Materials and Methods

2.0 The Study Area Description

The study was conducted in Kebbi State Nigeria around Anguwar Kade and Gwabbare Sakke Village respectively all in Gwandu Local Government Area. Geographically, the study area lies between latitude 12⁰30'8" North and longitude 4⁰38'33" East, and the area falls within the Sudan savanna ecological zone and characterized by the open woodland with scattered trees such as Parkia biglobosa, faidherbia albida, Adansonia digitata, Acacia nilotica, Khaya senegalensis etc. The average annual temperature of the area is 32^0c, annual precipitation in the area averages 900mm, while the humidity level of the area is at an average of 26% (Anon, nd). As of 2006, the estimated population of Gwandu LGA is one hundred and fifty one thousand, and seventy seven people (151,077) NPC (2006), inhabitants with the majority of the area’s populace made up of members of the Fulani and Hausa ethnic divisions. The Fufulde and Hausa Language are extensively spoken in the area while the religion of Islam is commonly practiced in the area. Farming is the major occupation of the people of Gwandu LGA with crops such as Groundnut, Rice, Millet, Sorghum, Onions, Late millet and sugar cane grown in large quantities in the area. Trade also booms in the area with the LGA hosting several markets such as the Dodoru market where the area’s dwellers go to buy and sell a plethora of commodities. Other important economic activities that are popular in Gwandu

LGA include cattle rearing and the making and sales of the popular kilishi snack (Anon, nd).

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Fig. 1: Map of Kebbi State Showing Location of the Study Area (Gwandu LGA)

Design

Fieldlayout and Experimental DesignThe study was conducted on farmer’s field to assess the soil fertility status under the canopy cover and outside the canopy cover of Faidherbia albida . To collect data on soil physical and chemical properties, ten (10) isolated trees of the species grown on similar site conditions were randomly selected on farmer’s farms. Radial distance based soil sampling (under the canopy, near to canopy and outside the canopy) was adopted (Figure 2). Three canopy positions, one at 50% of the canopy radius (from the tree trunk, called mid canopy), second at 50%at the extreme end of the canopy (from the mid canopy position, called canopy edge) and the third at 100% much beyond the canopy (far away from the canopy edge, called canopy gap) were demarcated. Experimental, design used was 1x3 arrangements of treatments (three radius) in Randomized Complete Block Design (RCBD) replicated 10 times (10 scattered trees of each species).

Data Collection

A total of 60 composite soil samples were taken at two different depths (0-15cm and 15- 30cm) at three distances (radius) in four different directions (North, South, East and West) of each tree. The soil samples collected were analyzed for soil texture, soil reaction(pH), soil organic carbon (SOC), cation exchange capacity (CEC), total nitrogen (TN), available phosphorus (AvP), potassium (K), calcium (Ca), magnesium (Mg) and sodium (Na) to assess soil fertility status.

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Fig. 2: Design of Soil Sampling where N is North, S is South, E is East, W is West, UC is under the canopy, NC is near to the canopy edge and FC is far away to the canopy.

Soil Laboratory Analysis

Soil laboratory analysis was conducted on the following parameters:

Soil organic carbon (SOC) was analyzed using the walkley-Black Oxidation method (Chesworth, 2008), total nitrogen (NT) using the Kjeldhal method (Jackson, 1958), available phosphorus (AvP) using the Olsen method (Olsen and Sommers, 1982), cation exchange capacity (CEC) using the ammonium acetate method (Houba, et al.,1989), soil reaction (pH) was determined using a pH meter (Van Reeuwijk, 1992). Soil particle size (soil texture) composition was analysis using the hydrometer method (Bouyoucos, 1962). Flame photometer method (Jackson, 1958) was used to determine potassium (K) and sodium (Na) of the soil, calcium (Ca) and magnesium (Mg) concentration of the soil was determined using atomic absorption spectrophotometer (Jackson, 1958). Data generated from soil analyses is presented in the results tables in chapter four.

RESULT PRESENTATION

The result of some physical and chemical properties of the soil are shown in table 4.1, 4.2 and the interpretation was based on recommendations of Esu (1991), Bruce (1997) and FAO (2021).

Table 3.1: Soil Textural Classes of Different Canopy Positions under Faidherbia albida and Parkia biglobosa Speciesat 0-15cm and 15-30cm Soil Depths

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Sources: Field data 2021

In this study, the result (Table 3.1) shows that the mid canopy of Faidherbia albida recorded loamy sand textural class while canopy edge and canopy gap recorded sand textural class.

Table 3.2: Soil Fertility Status of Different Canopy Positions under Faidherbia albida

Tree Species at 0-15cm and15-30cm Soil Depths

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Status Acidic

Source: Field data 2021

The results (Table 3.2) shows soil fertility status under Faidherbia albida tree species at different canopy positions. The pH of the soil is slightly acidic in the three canopy positions. Organic carbon, available phosphorus and calcium showed low status in both mid canopy, canopy edge and canopy gap, while the Cation Exchange Capacity (CEC), Potassium, Magnesium and Sodium in the three canopy positions recorded medium status. Total nitrogen was found high under the tree canopy positions.

DISCUSSION

Effect of Faidherbia albidaTree on Soil Physical Properties

The soil textural class is an important characteristic of a soil and gives a general picture of the soil physical property (Prasada and Power, 1997). In Faidherbia albida, the soil textural class in the study area changed from sand at canopy edge and canopy gap to loamy sand at mid-canopy (table 3.1). The findings of this study disagreed with the findings of Kmara and Haque (1992), Tadesse et al., (2001) and Abebe et al., (2001) who reported no significance difference in the soil texture under and outside the canopy of F. albida, Milletia ferrugeniaand Cordia africana trees respectively in Ethiopia.

Effect of Faidherbia albidaTree on Soil Chemical Properties

The Soil pH result (Table 3.2) shows that all the canopy positions of F. albida tree species were slightly acidic. According to Komicha et al.(2018), pH of the soil significantly increased as radial distance from the tree trunk increased under F. albida.The level of organic carbon under the mid canopy, canopy edge and canopy gap (Table 3.2) shows there is no variation among the canopy positions. The results of this study disagreed with the findings of researchers such as Nyberge and Hogberg (1995), Tadesse et al. and Abebe et al. (2001), Zebene and Goran Agren, (2007) whose reported an increase in soil organic carbon under the trees compared to away from trees. Also according to Abebe (2006) there was significant decrease in soil organic carbon with increasing distance away from the tree trunk in Harerge highlands, Ethiopia.

The total nitrogen results (Table 3.2) shows high level of total nitrogen in the soil under the three canopy positions of F. albida. This finding conform with that of Anim- Kwapong, (2006) who reported that studies across the globe have documented significant increases in nitrogen stocks under fertilizer trees compared to crop monocultures. Also the results of this finding agreed with the findings of Akinnifesi et al. (2010) that shows in gliricidia-maize-pigeon pea intercropping in southern Malawi 191-302 Kg Nha ^-1 could be realized from gliricidia prunnings under research farms.

The available phosphorus in the soil under the three canopy positions of Faidherbia albidatree species was found low (Table 4.2). This result disagreed with the finding of Palm, et al. (1997), according to him empirical studies have documented higher soil phosphorus concentrations and uptake by crops in the presence of fertilizer trees in research farms.

The Cation Exchange Capacity (CEC) level in the soil under the three canopies of F. albidatree species was found at medium level (Table 4.2), this findings agreed with the findings of Sail (1992), who reported that cation exchange capacity increases notably beneath

F. albida.Potassium, Sodium and Magnesium levels were at medium level (Table 3.2) under the mid-canopy, canopy edge and canopy positions of F. albida. This findings agreed with Boffa (1999) whose reported that, increases in soil cation concentrations usually results from recycling through the biomass of fertilizer trees. Calcium concentration level in the soil under the three canopies positions of F. albidawas found low (Table 3.2). This finding goes contrary to the findings of Kamara and Haque (1992) who’s reported that several studies indicated medium to higher calcium concentration under Faidherbiathan in the open.

Conclusion

The study indicated that, there was a dominance of slightly to medium acidic soils under Faidherbia albidatree canopies in the study area with high level of nitrogen, medium level of cation exchange capacity, potassium, magnesium, sodium and low level of available phosphorous and calcium. The soil physical properties changed from sandy soil in canopy gap (outside the canopy) to loamy sand under Faidherbia albidacanopy (mid and edge canopies).

Recommendations

Based on this research finding, the following recommendations were suggested:

1. Farmers should Retain Faidherbia albidatree on their farms for its importance in soil fertility enhancement so as to improve food security of their households.

2. Crops that can tolerate slightly to medium acidic soils should be cultivated near and under the canopies of F. albida

3. Further study on the factors responsible for low level of some soil nutrients under the canopies of Faidherbia albidain the study area is recommended.

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