Optimization of Value Chain Crop Yields in the Nigerian
Agricultural Transformation Agenda Through Soil
Survey and Land Evaluation
By
Ivara Ejemot Esu, OFR, FSSSN
Department of Soil Science, Faculty of Agriculture
University of Calabar, Calabar , Nigeria
*An Invited Paper Presented at the 37th Annual Conference of the Soil Science Society
of Nigeria, Lafia, Nasarawa State, March 11 – 15, 2013.
What is the Nigerian Agricultural
Transformation Agenda?
 A policy conceived by the President Goodluck Jonathan’s
Administration as a major tool to help progress towards
food security, poverty reduction, employment generation
and unprecedented industrialization of the country.
 To achieve a hunger-free Nigeria through an agricultural
sector that will drive income and transform the country
into a leading player in global food markets.
 To create wealth for millions of Nigerian farmers.
 Focuses on the development of agricultural value
chains.
What is Agricultural Transformation?
 Agricultural transformation is the process by which individual
farms shift from highly diversified subsistence-oriented
production towards more specialized production oriented towards
the market or other systems of exchange.
 The process involves a greater reliance on input and output
delivery systems and increased integration of agriculture with
other sectors of the domestic and international sectors.
 Increasing productivity at the farm level is absolutely necessary.
 The transformation action plan is focused on key aspects of
value chains.
 They include the provision and availability of improved inputs
(seeds and fertilizers), increased productivity and production as
well as the establishment of staple crop processing zones.
What is Agricultural Value Chains and
What are the Crops Included?
The action focuses on the development or promotion of the following
priority crops: Cassava, Rice, Maize, Sorghum, Cocoa, Oil palm,
Soybean, Cotton, Tomato, and Onions.
 Also focuses on other (non-crop) agricultural commodities such as
Dairy, Beef, Leather, Poultry and Fisheries.
 The commodity value chains are based on prioritization of the items
along comparative advantage in the six geo-political zones of the
country.
 It also involves reform in the input supply sector to stop direct
government involvement in the procurement, supply and distribution
of fertilizer and seeds to farmers.
 It also involves the establishment of private sector led commodity
trade and market development corporations for the value chains in
Nigeria.
Fundamental Flaw in the Initial Crafting
of the Agenda
Near to complete absence of emphasis on the importance of the soil
resource as the main engine to fuel the expected optimum yields of
the crops in the value chains .
Establishment of crop processing zones on which the cluster-based
value chain strategy are based, appear to have been mainly done on
the basis of climatic and vegetal regimes of the country.
Soil survey and land evaluation techniques have the capacity to most
appropriately guide farmers towards the selection and planting of the
various value chain crops in land areas best suited for their
production.
The techniques also have the capacity of clearly highlighting
limitations, if any, that prevent the soils from being suitable or
marginal for the intended land use type(s).
Thus, helps to pinpoint soil management issues which may militate
against optimum crop production on such soils.
Objectives of Paper
(i) To outline the meaning, purposes and methodologies of soil
surveys.
(ii) To outline the definition, methodology and usefulness of the
various land evaluation systems in use.
(iii) To establish a nexus between soil survey, land evaluation
and optimum yield of crops in the value chains of the
Nigerian Agricultural Transformation Agenda.
What is Soil Survey?
 Soil is often perceived as a continuum but actually, differences
occur in soils, vertically (profile) and horizontally (polypedons)
within short distances.
 Soils differ in depth, wetness, texture, reaction, sodicity, salinity,
nutrient content, etc.
 Soil surveys provide a scientific inventory of the soils occurring
within a specific land area (soil resource inventory).
 Soil survey involves the systematic examination, description,
classification and mapping of soils in a specified land area.
 It is a major pre-requisite for land-use planning and sustainable
development especially in agriculture.
Implementation Agencies of Soil Survey
 In developed countries like the USA and Canada, it is a co-operative
effort coordinated by USDA or Canadian Department of Agriculture.
 Cooperating Agencies include
(a) Natural Resources Conservation Service
(b) Bureau of Land Management
(c) Forestry Service
(d) Geological Survey
(e) Agricultural Experiment Stations of Universities in various States,etc.
 Detailed soil surveys are organized for each county – Equivalent to
Our Local Government Areas.
 In Nigeria: FDALR – Established in the 1980s
- Abolished soon after the production of the reconnaissance/
exploratory survey at 1:650,000 in 1991.
- Current Efforts being made to commence semi-detailed soil surveys.
Table 1: Kinds/Intensity/Order of Soil Survey
Kind/Intensity/Order
Purpose
Schematic/extremely To promote public
low intensity/6th
awareness about soils
order
of a broad region.
Approximate
Scales
≥ 1:5,000,000
Minimum size
Delineation/Transect
Spacing
> 4,000ha
Exploratory/very low
intensity/5th order
Generalize soil maps
to establish major soil
regions.
1:1,000,000
to
1:250,000
250 – 4,000ha
Transect spacing
5km x 10km
Reconnaissance/low
intensity/4th order
To identify possible
areas for more
intensive soil survey.
1:250,000
to
1:100,000
40 – 400ha
Transect spacing
1km x 1km
Semi-Detailed/
medium intensity/3rd
order
For pre-investment
feasibility
assessment.
100,000
to
50,000
2.4 – 25ha
Transect spacing
300 x 500m
Detailed/high
intensity/2nd order
Detail planning of
Agricultural projects.
50,000
to
25,000
1 – 4 ha
Transect spacing
100 x 200m
Very Detailed/V-high
intensity/ 1st order
For planning
experimental sites.
< 1:10,000
< 0.607ha
50 x 100m
Procedures of conducting soil surveys
 Rarely are soil surveys carried out these days without remote
sensing data. However, there are two main methods of conducting
soil surveys;
(i) Conventional methods involving Rigid Grid and Grid methods
(ii) Methods involving Remote Sensing Data such as;
(a) Air Photos
(b) Satellite Imageries e.g. Landsat, GeoEye, Spot Image, RapidEye, etc.
(c) Digital Soil Mapping.
Products of Soil Survey
They are two main products of soil survey; Soil Map and (b) Soil Survey
Report
Soil Survey Report
Soil Survey Report often accompanies the soil map and normally
contains but not limited to;
(a) A description of the environment of the survey area.
(b) Methods of investigation
(c) Description of mapped soils (soil mapping units)
(d) Soil data interpretation and land use
(e) Soil management recommendations and appendices showing profile
descriptions, analytical data, etc.
Land characteristics and land qualities often of great interest in
soil data interpretation include (i) Slope (ii) Effective soil depth
(iii) Soil texture/structure (iv) Drainage (v) Salinity (vi) Soil pH/Exch.
Al3+ (vii) Organic carbon (viii) Major plant nutrients (NPK) (ix)
CEC/Exch. Bases (Ca2+, Mg2+, K+) (x) Base saturation (xi)
Micronutrients (Zn, Cu, B, Fe, Mn)
Table 2: Land Characteristics/Land Qualities Used for
Evaluation of Soils for Agricultural Use in General
Extrinsic Properties
Land characteristics
Highly Suitable
(S1)
Moderately
Suitable (S2)
Marginally
Suitable (S3)
Not Suitable
(N1)
Slope, %
<4
4-10
10-25
>25
Surface stoniness, %
<2
2-20
2-20
>50
Surface rockiness, %
<2
2-20
2-20
>50
Flooding, months
0
<1
1-3
>3
Erosion, Tm/ha/year
<10
10-20
20-60
>60
Ploughing
No problems
Limited
Severe
Very severe
Precipitation, mm
>1000
100-600
600-300
<300
Frost, Ta<00, months
<1
1-3
3-6
>6
Intrinsic Properties
Land characteristics
Highly Suitable
(S1)
Moderately Suitable
(S2)
Marginally
Suitable (S3)
Not Suitable
(N1)
Effective depth, cm
>120
120-70
70-30
<30
Texture
Balanced
Moderate heavy
Heavy
Light
Coarse fragments, %
<10
10-30
30-60
>60
Structure
F, md, 3,2
C, 1
sg, 0
ms, 0
Compact, cem, gr, cm
Absent
md, <60
Md,>20 or
st,>60
st, <30
Available water, mm
>100
100-60
60-20
<20
Internal drainage
Without hydro
Hydro>80cm
Hydro>40cm
Hydro a 0cm
Permeability, cm/hr
>2
2-0.5
0.5-0.1
<0.1
Organic matter, %
>5
5-2
2-1
<1
CEC, cmolkg-1
>40
40-20
20-10
<10
pH
7.3-6.7
6.7-5.5 or 7.38.0
5.5-4.5 or
8.0-9.0
<4.5 or >9.0
Carbonates, %
>7
7-15
15-25
>25
Salinity, dSm-1
<2
2-6
6-12
>12
Chemical Fertility Properties
Land characteristics
Highly
Suitable
(S1)
Moderately
Suitable (S2)
Marginally
Suitable (S3)
Not Suitable
(N1)
Total N (%)
>0.15
0.10-0.15
0.05-0.10
<0.05
Available P (mgkg-1)
>20
15-20
5-15
<5
Extractable K (cmolkg-1)
>0.5
0.3-0.5
0.3-0.1
<0.1
Zn (mgkg-1)
>15
10-15
10-5
<5
Cu (mgkg-1)
>10
5-10
1-5
<1
Mn (mgkg-1)
>50
30-50
15-30
<15
Fe (mgkg-1)
>20
10-20
10-5
<5
B (mgkg-1)
>0.5
0.5-0.7
-
<0.5
What is Land Evaluation?
Land evaluation can be defined in general terms as the assignment of
land performance when used for specific purpose(s).
 It may be evaluated directly e.g. through the collection and processing
of crop-yield data (Rare in our situation).
Indirectly, diagnostic criteria which influence land performance in a
reasonably predictable manner and that this performance can be
deducted from the observation of those properties.
In the indirect method, land evaluation involves the execution and
interpretation of surveys and studies of landforms, soils, vegetation,
climatic and other aspects of land in order to identify and make
comparisons of promising kinds of land use in terms applicable to the
objectives of the evaluation.
Land characteristics/land qualities used in land evaluation are often
obtained during a systematic soil survey.
Questions Land Evaluation Process
Seek to Answer?
(i) What are the properties of the land of each soil mapping unit in a soil
map and which type of use offers the best sustainable production
and/or benefits?
(ii) What is the present land use and what alternative uses are physically
possible and socially, economically and environmentally relevant?
(iii) What will happen if present practices remain unchanged? And how
can the present practices be improved?
(iv) What inputs are needed to achieve the desired sustainable
production and minimize the adverse effects and risks?
(v) What are the adverse physical, economical, social and environmental
effects and risks and what are the benefits of a given land use
system or practice?
Major Systems of Agricultural
Land Evaluation
Land evaluation systems currently in use belong generally to four main
groups:
(i) Capability or Categoric systems e.g. USDA Land Capability
Classification (Klingebiel & Montgomery, 1961).
(ii) Special purpose systems e.g. FAO Framework for Land Evaluation
(FAO, 1976).
(iii) Parametric systems e.g. The Storie Index (Storie, 1933, 1978),
Riquier, Bramao and Cornet System (1970).
(iv) Crop-Specific Assessments (Sys and Riquier, 1980; Sys, 1985).
Land Capability Classification
 Based on detailed soil survey (1:10,000 – 1:24,000) in the USA
 Groups soil mapping units “primarily on the basis of their capability to
produce common cultivated crops and pasture plants over a long period
of time”.
 Capability groups are made of three levels (a) Land classes (b) Land
subclasses (c) Land units
 Land capability classes are eight (I-VIII)
Classes 1 – Best land, little or no limitation
Class I, II & III – Land suited for cultivation with increasing limitation
Class IV – Fairly good but has serious limitations but best use in pasture.
class V, VI & VIII – Not good for cultivation of common crops but ok for
grazing or forestry.
Class VIII – Land suited for wildlife, recreation or watershed protection.
Extreme steepness, roughness, wetness, erodibility, stoniness, etc unsafe
for economic cultivation, grazing or forestry.
 Land Subclasses, expresses kinds of limitation, e(erosion), w(wetness)
s(soil conditions) and c(climate).
 Land Units, kind of management and same kind of conservation
treatment e.g. IIe-1, IIe-2, IIIes-1, IIIes-2 etc.
Land Suitability Classification (FAO, 1976)
 Contains two Orders – Suitable (S) and Not Suitable (N)
 Suitable Order has three(3) classes – Highly Suitable (S1),
Moderately Suitable (S2) and Marginally Suitable (S3)
 Not Suitable Order has two(2) classes – Currently Not Suitable (N1)
and Permanently Not Suitable (N2).
 Suitability Subclasses: Indicate kinds of limitations e.g. moisture
deficiency, erosion hazard, but no subclasses for S1, but subclasses
exist for others e.g. S2e, S3d, etc.
 Suitability Units: Subdivisions of Subclasses differing in detailed
aspects of their production characteristics or management
requirements. S2e-1, S2e-2, etc.
Parametric Systems
 Parametric systems like all numerical correlations are a simple
quantified expression of soil productivity.
 Their reliability depends, however, heavily on the choice of the factor
determinants, their weighting and the validity of the assumed
interactions between the factors.
 All factors with a relevant impact on the land use potential are
allocated a numerical value ranging from 1.0 or 100 (for the highest
potential) and almost 0.0 (for the lowest potential).
 The final index is obtained by either multiplying or adding the
individual rating values. This index is finally converted into a yield
level or productivity class.
Example: (i) Riquier et al (1979)
N
IP =
H X D X P X T X or X O X A X M
S
Where: IP=Index of Productivity, H=Soil Moisture, D=Drainage
Condition, P=Effective soil depth, T=Texture/Structure, N=Base
Saturation, S=Soluble salts, 0=Organic Matter, A=Nature/CEC
of clay, M=Mineral Reserve.
According to the resulting index of productivity, the soil is
assigned to one of five productivity classes:
Class1= Excellent with rating
Class2= Good with rating
Class3= Average with rating
Class4= Poor with rating
Class5= Extremely poor with rating
-
65-100
35-64
20-34
8-19
0-7
Crop Specific Assessments (Sys, 1985)
 Combines the FAO Framework for land evaluation (Land suitability
classification) with the parametric system.
 What is essential to the system is that the land characteristics/land
qualities are compared with the crop requirements of each land
utilization type.
 Evaluation procedure consists of three(3) phases
(i) Collection of the necessary land characteristics/land qualities.
(ii) Determination of the requirements of the land utilization type(s)
(iii) Evaluation senso-stricto by comparing land characteristics/qualities
with the crop requirements and rating them.
Table 3: Land Requirements for Suitability Classes for Oil palm
Cultivation (Modified from Sys, 1985 in Ogunkunle, 1993)
Land Qualities
Suitability Classes
SI1
(85-95%)
Climate (C):
SI2
(60-85%)
S2
40-60%)
S3
(25-40%)
N1
(25-40%)
N2
(0-25)
Annual rainfall (mm)
>2000
1700-2000
14501000
12501450
-
<1250
Length of dry
season (months)
<1
1-2
2-3
3-4
-
>4
>29
Mean annual
maximum temp. (oC)
27-29
24-27
22-24
-
<22
Average daily
minimum temp. (oC)
>20
18-20
16-18
14-16
-
<14
Mean annual temp.
(oC)
>25
22-25
20-22
18-20
-
<18
Relative humidity
(%)
>75
70-75
65-70
60-65
-
<60
Land Qualities
Suitability Classes
S11
(85-95%)
Topography (t):
S12
(60-85%)
S2
40-60%)
S3
(25-40%)
N1
(25-40%)
N2
(0-25)
Slope (%)
0-4
4-8
8-16
16-30
Wetness (w):
Flooding
F0
F0
F1
F2
Drainage
Imperfect
Mod. Well
Mod. Well
Poor, aeric
Poor,
drainable
Poor,
v.poor,
not
drainable
Soil Physical
Properties (s):
Texture
CL, SCL, L
CL, SCL, L
SCL
SCL-LFS
Any
C, SC
Structure
Blocky
Blocky
Coarse fragments 3-10
(Vol%), 0-10cm
Depth (cm)
>100
>30
-
-
F3
Massive,
single grain
10-15
15-35
35-55
-
>55
90-100
50-90
25-50
-
<25
Land Qualities
Suitability Classes
SI1
(85-95%)
SI2
(60-85%)
S2
40-60%)
S3
(25-40%)
N1
(25-40%)
N2
(0-25)
Cation exchange
capacity (mEq/100g)
<10
8-10
6-8
<6
-
-
Base saturation (%)
>35
20-35
<20
-
-
-
pH
5.5-6
5.5-6
5.5-6
6.5-7
<4,>7.0
<4,>10
Organic carbon (%),
0-15cm
>1.2
1.2-0.8
<0.8
-
-
-
K (mole fraction)
>1.75
1.5-1.75
1.2-0.5
<1.2
<1.2
<1.2
Mg: K ratio
>3.5
>3.5
2-3.5
1.2
-
-
<1
1-2
2-3
3-4
4-8
>8
Fertility (t):
Salinity and
Alkalinity (n):
EC (mmhos/cm)
F0, no flooding; F1, 1-2 flooding months in >10years; F2, not more than 2-3months in 5
years out of 10; F3, 2-4 months almost every year; F4, >4months in almost every year.
CL, clay loam; SCL, sandy clay loam; L, loam; LFS, loamy fine sand; C, clay; SC, sandy clay.
Table 4: Ratings of Limiting Characteristics (Ogunkunle, 1993)
Limitation
Rating
Slight-None (S11)
100-95
Slight (S12)
94-85
Moderate (S2)
84-60
Severe (S3)
59-40
Very severe (N1)
39-0
(1) Can be corrected (N2)
39-20
(2) Cannot be corrected (N2)
19-0
Table 5: Suitability class scores for representative two
pedons of the soil series in NIFOR (Ogunkunle, 1993)
Land Quality
Ratings
Alagba series Orlu series
Climate (C):
Annual rainfall
S1(95)
S1(95)
Length of dry season
S2(85)
S2(85)
Mean annual maximum temp.
S1(100)
S1(100)
Average daily minimum temp.
S1(95)
S1(95)
Relative humidity
S1(100)
S1(100)
Topography (t):
Slope (%)
S1(95)
S1(95)
Wetness (w):
Drainage
S1(100)
S1(100)
Soil Physical Properties (s):
Texture and structure
S1(95)
S2(85)
Volume of coarse fragments
S1(100)
S1(100)
Soil depth
S1(100)
S1(100)
Land Quality
Ratings
Alagba series
Orlu series
Fertility (t):
Cation exchange capacity
S2(85)
S2(85)
Base saturation
S1(95)
S1(95)
pH
S2(85)
S2(85)
Organic matter content
S2(85)
S1(100)
Exchangeable K
S3(60)
S1(100)
Exchangeable Mg
S1(100)
S3(40)
K mole fraction
S3(40)
S3(40)
Mg: K ratio
S1(100)
S3(60)
Salinity and Alkalinity (n):
Electrical conductivity
S1(100)
S1(100)
Aggregate suitability:
Potential
S1(75)
S2(70)
Actual
S3(35)
S3(33)
Procedure for Evaluation in the Crop Specific
Assessment Method
 Match soil characteristics (climatic, topography, wetness, soil physical
characteristic, soil fertility, salinity/alkalinity) with the crop requirement for
each of these land qualities using the rating table (slight to none, 100-95;
slight, 94-85… severe 59-40 and thus create a suitability class scores
table e.g. Table 5.
 Note that aggregate suitability of each land quality group is its most
limiting characteristics because of Leibig’s Law of the minimum which
states that “growth is controlled not by the total amount of resources
available, but by the scarcest resource (limiting factor)
 Calculate the index of productivity/suitability (IP) for each soil unit by using
the equation below:
Where: A = Overall lowest characteristic rating within all the land quality groups
B, C, ……F = The lowest characteristic rating for each of the land quality
groups e.g. Climate (c), Topography (t). . . . Chemical fertility (f)
 Determine potential and current index of productivity by noting that
in potential index of productivity (IPp), fertility values such as K mole
fraction, Mg: K ratio, and other fertility characteristics which can
easily be corrected by the application of fertilizer(s) are not
considered in rating for the fertility land quality group but these are
considered when rating for Current/Actual productivity (IPc). As an
example in the Table 5 just considered index of productivity for
Alagba series is calculated as:
(f)
(c)
(t)
(w)
(s)
and
(f)
(c)
(t)
(w)
(s)
Table 6: Current and potential yields of crops in the value
chain of the Nigerian Agricultural Transformation Agenda
Yield
range
(t/ha)
Mean
(t/ha)
Potential
yield
(t/ha)
Current
yield
(t/ha)
Cassava
12.5-60
24.70
28.4
Maize
0.48-8.0
3.20
Sorghum
1.50-5.0
Soybean
Rice
Crops
Cotton (lint)
Tomato
Yield gap
t/ha
%
12.5
15.90
127
4.0
1.57
2.43
155
3.00
3.2
1.18
2.02
171
0.64-20
1.21
2.0
1.21
0.79
66
2.90-7.0
4.20
5.4
1.98
3.42
173
1.29
3.82
1.29
2.53
196
30.00
6.00
24.00
400
-
15.0-30.0 6.00
Oil palm (ffb) 2.0-7.0
4.0
16.00
6.00
10.00
167
Cocoa (dry
bean)
0.5
1.50
0.30
1.20
400
0.3-1.0
Conclusion
 A very close nexus exists between soil survey, land evaluation and
optimum crop yields in any given land area.
 Soil survey generates the soil map and the land characteristics/land
qualities of the map units.
 The process of land evaluation matches the properties of the soils
with the requirements of each crop for optimum production.
 Land evaluation also results in the highlighting and drawing
attention to certain management problems such as low nutrient
fertility, soil acidity or alkalinity, salinity, low organic matter content,
shallow effective soil depth and soil erosion hazard, as well as
helping to seek for appropriate solutions.
 Soil survey and land evaluation may thus be said to be a
sine qua non to the optimum yield of crops like those included in
the value chains of the Nigerian Agricultural Transformation Agenda.
For your