ABSTRACT
This study was conducted to determine the physical, chemical and mineralogical properties of soils as well as the distribution of` phosphorus (P) forms in soils supporting rice production in Abia State, Nigeria. A total of 54 composite soil samples were collected from the depths of 0-20cm, 20 – 40cm and 40 – 60cm respectively from 18 different farms, located at Amaeke-Abam, Ahaba-Imenyi, Bende, Urbanu-Ibeku and Uzuakoli in Abia State. The soil samples were subjected to routine physical and chemical analysis in the laboratory. Results obtained showed that the soils varied in texture from sandy clay loam at the surface (0-20cm) to sandy clay at lowest depth (below 40cm-60cm).The soils were very acidic (pH 4.74-5.00) and the pH increased insignificantly with increase in soil depth. Organic matter level was moderate (ranging from 36.60g/kg to 24.00 g/kg) and decreased with increase in depth. ECEC was low all through the three depths (ranging from 19.40 cmol/kg to 20.40cmol/kg).Total exchangeable acidity decreased down the depth, with mean values of 3.09cmol/kg, 2.85cmol/kg and 2.47cmol/kg and these were rated above the critical value of 2.00cmol/kg Al toxicity. Apart from exchangeable Ca and magnesium, values of Na and K were low, with values increasing with profile depths. Exchangeable calcium had a range of 6.09cmol/kg to 6.44cmol/kg in the 0-20cm depth and 40-60cm depth respectively. Exchangeable K was low in the top soil (0.16cmol/kg) and increased above the critical value of 0.2cmol/kg in the sub soils. Exchangeable Mg and Na contents were in the ranges of 9.96cmol/kg (top soil) to 11.61cmol/kg (sub soil) and 0.08cmol/kg (top soil) to 0.09cmol/kg (sub soil) respectively. The available phosphorus was low (<15.0mg/kg) and increased along the profile. Total nitrogen was low (1.57g/kg) at 0-20cm with values decreasing with depth. The mineralogy of sand sized fractions was predominantly quartz with little quantity of kaolinite. Silt fraction mineralogy showed the presence of quartz, (23.82% - 62.07%), microcline (1.13% - 2.65%), kaolinite (0.21% - 0.26%) and some traces of the other minerals. Mineralogy of the clay particles showed that the soils studied had mixed mineralogy dominated by quartz (12.13% – 83.22%), little quantity of kaolinite (3.12% – 5.67%) and microcline (1.97% – 4.84%). The abundance of the P fractions was in this order Ca-P > Fe-P > Al-P > Org.P > Ca-P. It was observed that only Al-P significantly varied between depths. The correlation study showed that Al-P had a positive significant (P<0.01) correlation with total nitrogen, but slightly and positively correlated with exchangeable magnesium, total exchangeable bases, base saturation and effective cation exchange capacity. Fe-P significantly (P<0.05) and positively correlated with organic matter, organic carbon, exchangeable H and TEA. Ca-P had a significant (P<0.05) and positive correlation with exchangeable Al and silt. Organic P correlated positively and significantly (P<0.05) with exchangeable Mg and Ca, TEB and ECEC. These soils supporting rice production in Abia State will require good application of organic manure and mineral fertilizers to enhance their fertility for sustainable rice production.
TABLE OF CONTENTS
Title Page i
Declaration ii
Certification iii
Dedication iv
Acknowledgement
v
Table of
Contents
vi
List of
Tables
x
List of
Figures
xi
Abstract xii
CHAPTER
1: INTRODUCTION 1
1.1 Objectives of the Study 3
CHAPTER
2: REVIEW OF RELATED LITERATURE 4
2.1 Soil Properties 4
2.1.1 Texture 4
2.2 Soil Chemical Properties 5
2.2.1 Soil pH 6
2.2.2 Organic
matter 8
2.2.3 Cation
exchange capacity 10
2.2.4 Base
saturation 11
2.2.5 Total
nitrogen 11
2.2.6 Available
phosphorus 13
2.2.7 Exchangeable
acidity 14
2.2.8 Exchangeable
potassium 15
2.2.9 Calcium
and magnesium 17
2.3 Soil Mineralogy 18
2.4 Overview of Phosphorus 19
2.5 Phosphorus Forms 23
2.6 Soil Phosphorus Pools 26
2.7 Soil P Transformations 28
2.7.1 Weathering and precipitation 29
2.7.2 Mineralization
and immobilization 29
2.7.3 Adsorption
and desorption 29
2.8 The Phosphorus Cycle 30
2.9 Distribution of Phosphorus in Soils 31
2.10 Fractionation of Soil Phosphorus 32
2.11 Fractionation of Inorganic Phosphorus 34
2.11.1 Chang and Jackson fractionation method 34
2.11.2 Hedley fractionation method 35
2.12 Mineral Nutrient Requirement of Rice 36
2.13 Phosphorus Nutrition in Rice 42
2.13.1 Phosphorus deficiency: occurrence and symptoms 43
2.14 Rice Production in Nigeria 45
2.15 Rice Growing Culture/Environment 47
2.16 Climate and Soil Requirement of Rice 51
2.17 Rice Soils 53
2.18 Soil Resources in Southeastern Nigeria 54
2.19 Soil Resources for Rice Production in Southeastern Nigeria 54
CHAPTER 3: MATERIALS AND METHODS 56
3.1 Study Area 56
3.2 Soil Sampling and Sampling Collection 56
3.3 Laboratory Analysis 58
3.3.1 Particle size distribution 58
3.3.2 Soil pH 58
3.3.3 Organic carbon 59
3.3.4 Total
nitrogen 59
3.3.5 Exchangeable acidity 60
3.3.6 Exchangeable
bases 60
3.3.6.1 Determination of exchangeable magnesium 61
3.3.6.2 Determination of exchangeable calcium 61
3.3.6.3
Exchangeable potassium and sodium determination 61
3.3.7 Effective cation exchange capacity (ECEC)
(summation of cations) 62
3.3.8 Determination of various forms of phosphorus (P) 62
3.3.8.1 Available phosphorus 62
3.3.8.2 Total phosphorus 63
3.3.8.3 Organic phosphorus 63
3.3.9 Determination of inorganic phosphorus 64
3.3.9.1 Aluminum phosphate
(Al-P) 64
3.3.9.2 Iron phosphate (Fe-P) 65
3.3.9.3 Calcium phosphate (Ca-P) 65
3.3.10 Soil mineralogy 65
3.4 Data Analysis 66
CHAPTER 4: RESULTS AND DISCUSSION 67
4.1 Soil Physical Properties 67
4.2 Chemical Properties of the Soil 68
4.2.1 Soil pH 68
4.2.2 Soil organic matter 69
4.2.3 Total Exchangeable Acidity 69
4.2.4 Effective
Cation Exchange Capacity 70
4.2.5 Percentage
Base Saturation 70
4.3 Soil Nutrient Content 71
4.3.1 Total nitrogen 71
4.3.2 Available phosphorus 71
4.3.3 Exchangeable potassium 72
4.3.4 Exchangeable calcium 72
4.3.5 Exchangeable magnesium 73
4.3.6 Exchangeable Na 73
4.4 Variability of Soil Properties 74
4.5 Soil Mineralogy 74
4.5.1 Sand mineralogy at different depths 75
4.5.2 Silt mineralogy at different depths 80
4.5.3 Clay mineralogy at different depths 84
4.6 Distribution of phosphorus forms 90
4.6.1 Ca-bound phosphorus 90
4.6.2 Fe-bound phosphorus 90
4.6.3 Al-bound phosphorus 91
4.6.4 Organic phosphorus 91
4.7 Relationship Between
P forms and Soil Properties 93
4.7.1 Available phosphorus
(AV.P) 94
4.7.2 Iron phosphate (Fe-P) 95
4.7.3 Aluminum phosphate
(Al-P) 96
4.7.4 Organic phosphate
(Org- P) 97
4.7.5 Calcium phosphate
(Ca-P) 98
4.7.6 Total phosphate
(Total- P) 98
CHAPTER 5:
CONCLUSION AND RECOMMENDATIONS 99
5.1 Conclusion 99
5.2 Recommendations 99
References 100
LIST OF
TABLES
2.1 Nutrient
removal of rice crop (variety IR8) yielding 7.9 tons/ha
at
Maligaya Rice Research and Training Center, Philippines, 1979
dry
season. 43
2.2 Summary
of rice systems. 48
2.3 Rice
production systems in Nigeria, 2005 49
2.4 Rice
growing systems in the South-East Zone 50
2.5 Minimum, optimum and high temperatures
for rice growth at
different stages 52
3.1 Georeference positions of the sample
locations 57
4.1 Particle
size distribution in the soils. 68
4.2 Distribution
of soil chemical properties 69
4.3 Distribution
of nutrient contents in the soil 71
4.4 Variability
of the soil properties studied. 74
4.5 Minerals
identified in the soil 88
4.6 Differences in minerals identified in the
soil seperates 89
4.7 Distribution
of soil P fractions in the soil 92
4.8 Relationship
between P forms and soil properties 93
LIST OF FIGURES
2.1 Phosphate Structure 21
2.2 Influence of pH on the distribution of
orthophosphate species in solution 22
2.3 Relationship
between P absorbed by soil and P in solution 27
2.4 A Representation of the phosphorus cycle 30
2.5 Rice paddy area, production and yields in Nigeria (2000-2010) 46
4.1 Sand mineralogy at 0-20cm depth 77
4.2 Sand mineralogy at 20-40cm depth 78
4.3 Sand mineralogy at 40-60cm depth 79
4.4 Silt mineralogy at 0-20cm depth
81
4.5 Silt
mineralogy at 20-40cm depth 82
4.6 Silt
mineralogy 40-60cm depth 83
4.7 Clay
mineralogy 0-20cm depth 85
4.8 Clay
mineralogy 20-40cm depth 86
4.9 Clay
mineralogy 40-60cm depth 87
CHAPTER 1
INTRODUCTION
Phosphorus (P) is the second most important nutrient element
limiting agricultural production in most regions of the world (Holford, 1997). According to Schachtman et al., (1998), phosphorus is a vital plant macronutrient, making up about
0.2% of a plant's dry weight. It is an integral part of nucleic acids,
phospholipids and ATP. Phosphorus is an essential element that is useful in
plant for processes like photosynthesis, respiration, energy storage and
transfer, cell division and enlargement and others.
Soil P is found in different forms, such as organic and
mineral forms. Richardson (1994) stated that 20 to 80 % of P in the soil exists
in the organic form. About 80% of P in the soil is immobilized and unavailable
for plant uptake as a result of adsorption, precipitation, or conversion to the
organic form (Holford, 1997). In general, roots absorb
phosphorus as orthophosphate (H2PO4- and HPO42-).
Appropriate phosphorus nutrition is needed by the rice
plant, for high grain yields. Phosphorus is particularly important to the rice
seedling during the time it is recovering from transplanting shock. Phosphorus
greatly stimulates root development in the young plant, thus increasing its
ability to absorb nutrients from the soil. It is important to rice plants because it promotes tillering, root
development, early flowering, and ripening.
Rice
is the seed of the grass species Oryza sativa (Asian rice) or Oryza
glaberrima (African rice). Rice is the most important grain with
regard to human nutrition and calorie intake, providing more than one fifth of
the calories consumed worldwide by humans. It is an important component of food
consumption pattern in Nigeria (Iheke and Nwaru, 2008; Anuebunwa, 2007). It is
the 4th most important crop in terms of calories consumed in Nigeria
next to sorghum, millet and cassava (Cadoni and Angelucci, 2013). Werblow
(1997) observed that owing to its high energy value and ease of preparation, it
has replaced these major staples. It is important for its carbohydrate content
and has higher available carbohydrate than maize and wheat. It contains higher
lysine and other sulphur containing amino acids (Christou, 1994).
Nigeria
is the largest rice producing country in West Africa and the second largest
importer of rice in the world (Cadoni and Angelucci, 2013). Nigeria produces
over 40% of the regions total production (Singh et al., 1997). Rice
according to West Africa Rice Development Agency (WARDA, 2004), has been
recognized as a preferred staple in Nigeria, with per capita consumption,
rising from 15.4kg/year to 25.4kg between 1980s and 2006. Nigeria consumes
about 5.4 million metric tonnes of rice annually. This demand cannot be met by
annual domestic output of rice which still hangs around 3.0 million metric
tonnes leaving the huge demand gap of about 2 million metric tonnes to
importation (Nto et al., 2014). Nigeria spends more than 356 billion naira (2.24 billion US
dollars) annually on rice importation (Adesina, 2013), to the detriment of our
scarce foreign exchange reserve. Nwachukwu et al., (2008) stated that out of 4.6
million hectares available for rice production, only 1.7 million hectares are
put to rice cultivation.
Rice
is grown virtually in all the agro-ecological zones in Nigeria (Akande, 2003),
however
one of the problems facing Nigeria is how to improve domestic rice production,
so as to significantly reduce domestic supply deficit and cut down on import
bills. Rice farmers in Nigeria are predominantly small holders, producing on
the average, 4.6 tons of paddies per year (Erenstein et al., 2003).
Nwite et al., (2012), noted that in spite of the potentials of Nigerian
inland valleys for agricultural use especially in the southeast, these areas
are yet to be fully exploited for rice
based cropping system. This is as a result of several constraint, such as poor
soil fertility (Ogbodo et al., 2012;
Nwite et al., 2012; Asawalam and Okonkwo, 2006; Ogbodo and Chukwu,
2012), inefficient weed and water management (Nwite et al., 2012), poor
leveling of rice fields, lack of appropriate and adequate fertilizer
application and growth disorders (Ogbodo, 2013).
Abundant
land suitable for rice production exists in Nigeria, but detailed soil studies
for sustained rice production is still limited. This study is designed to
contribute to the body of knowledge required to improve rice production in Abia
state.
1.1 OBJECTIVES
OF THE STUDY
i.
To determine the physico-chemical properties of swamp rice
growing soils in Abia State.
ii.
To determine the mineralogy of rice growing soils of Abia State.
iii.
To determine the distribution of the different forms of
phosphorus in the soils.
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