Use of phosphate rocks for sustainable agriculture Use of phosphate rocks for sustainable agriculture

172 Pages·2004·9.97 MB·English

FAO ISSN
FERTILIZER 0
5
AND PLANT 32
-0
13 1 NUTRITION 48
3 BULLETIN 8
FAO FERTILIZER AND PLANT NUTRITION BULLETIN
13
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Extensive research on the agronomic potential and actual
effectiveness of phosphate rocks (PRs) as sources of
phosphorus has been carried out in Africa, Asia, Latin
U
America and elsewhere. A wealth of information is s
e
available, but it is scattered among meeting proceedings, of
p
technical reports and scientific and other publications. This h
o
s
bulletin gives comprehensive coverage of the key topics ph
a
regarding the utilization of PRs in agriculture, including the te
r
o
latest information on PR research, and provides guidelines c
k
s
for the direct application of PR (DAPR) to the acid soils of f
o
r
the tropics and subtropics. The selected topics include: world su
s
t
PR deposits; characterization of PR sources; evaluation a
in
methodologies of PR sources for direct application; analysis ab
le
of the biophysical and farming factors that affect the a
g
agronomic effectiveness of PR sources, together with an ric
u
analysis of the socio-economic factors that influence the use ltu
r
e
and adoption of PR technologies as a capital investment to
trigger agricultural intensification; development and use of
decision-support systems for DAPR; soil P testing for PR
application; available technologies for enhancing the
agronomic effectiveness of indigenous PR sources;
environmental issues; legislation guidelines; and future
research areas and priorities.
ISBN 92-5-105030-9 ISSN 0532-0488
F
9 7 8 9 2 5 1 0 5 0 3 0 9 A
TC/M/Y5053E/1/1.04/1600 O
COVER PHOTOGRAPHS
Phosphate rock ore and mining in Khouribga, Morocco.
Abdelatif Belmehdi, IMPHOS, Morocco.
Phosphate rock broadcast application.
Efficient fertilizer use, 1988, FAO, Rome.
Good crop of improved maize. Honduras. FAO/17274/C. Sanchez.
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Food and Agriculture Organization of the United Nations
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Use of phosphate rocks FAO
FERTILIZER
AND PLANT
for sustainable agriculture NUTRITION
BULLETIN
13
Technical editing by
F. Zapata
Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture
Vienna, Austria

R.N. Roy
Land and Water Development Division
FAO, Rome, Italy
A joint publication of the
FAO Land and Water Development Division
and
the International Atomic Energy Agency
FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS
Rome, 2004
FRONTESPIZIO-DISCLAIMER.INDD 1 20-01-2004, 15:50
The designations employed and the presentation of material in this information
product do not imply the expression of any opinion whatsoever on the part
of the Food and Agriculture Organization of the United Nations or the International
Atomic Energy Agency concerning the legal or development status of any country,
territory, city or area or of its authorities, or concerning the delimitation of its frontiers
or boundaries.
ISBN 92-5-105030-9
All rights reserved. Reproduction and dissemination of material in this information
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acknowledged. Reproduction of material in this information product for resale or other
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Applications for such permission should be addressed to:
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or by e-mail to:
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© FAO 2004
FRONTESPIZIO-DISCLAIMER.INDD 2 20-01-2004, 15:50
Contents
LIST OF TABLES vi
LIST OF FIGURES viii
ACKNOWLEGEMENTS x
PREFACE xi
CONTRIBUTING AUTHORS xiii
LIST OF ABBREVIATIONS AND ACRONYMS xiv
EXECUTIVE SUMMARY xvii
1. INTRODUCTION 1
Phosphorus in the soil-plant system 1
The need for sustainable development 2
Addressing the P constraint in tropical acid soils 3
Use of phosphate rocks in industry and agriculture 3
Phosphate rocks as raw materials for P-fertilizer manufacturing 3
Phosphate rock for direct application in agriculture 4
Historical account of the use of phosphate rocks in agriculture 6
The bulletin 8
2. WORLD PHOSPHATE DEPOSITS 11
World phosphate rock production 11
World phosphate rock reserves and resources 12
Future trends in world phosphate rock production 15
3. CHARACTERIZATION OF PHOSPHATE ROCKS 17
Phosphate rock mineralogy 17
Sedimentary apatites 17
Igneous apatites 19
Other minerals in PRs 19
Phosphate rock solubility tests 21
Apatite solubility 21
Classifi cation of phosphate rocks based on solubility 23
Characterization methods 24
4. EVALUATION OF PHOSPHATE ROCKS FOR DIRECT APPLICATION 27
Phosphate-rock solubility tests 28
Solubility measurements using conventional chemical techniques 28
Kinetics of long-term PR dissolution 30
PR reactivity scales and crop yield response 31
Measurement of exchangeable P from PR by radioisotopic techniques 33
Reactions between phosphate rocks and soil 34
Soil incubation 34
Liming effect of PRs 35
Greenhouse tests 35
Comparison of PRs with standard fertilizers 37
iv
Effect of time 38
Relationship between PR solubility and crop P uptake 39
Field evaluation 39
5. FACTORS AFFECTING THE AGRONOMIC EFFECTIVENESS OF PHOSPHATE ROCKS, WITH A
CASE-STUDY ANALYSIS 41
Factors affecting the agronomic effectiveness of phosphate rocks 41
Reactivity of PRs 41
Soil properties 42
Climate conditions 45
Crop species 45
Management practices 46
Case studies 47
Mali 47
Madagascar 49
India 50
Indonesia 52
New Zealand 54
Latin America 54
6. SOIL TESTING FOR PHOSPHATE ROCK APPLICATION 59
Soil phosphorus reaction and soil testing 59
Conventional soil tests 60
Bray I test 60
Bray II and Mehlich I tests 62
Olsen test 63
Recently developed soil tests 64
Iron-oxide-impregnated paper test 64
Mixed anion and cation exchange resins 66
Isotopic 32P exchange kinetic method 67
7. DECISION-SUPPORT SYSTEMS FOR THE USE OF PHOSPHATE ROCKS 69
The need for a decision-support system for phosphate rocks 69
Conceptual basis for building a PR-DSS 69
Different types of DSS to predict PR performance 71
Mechanistic models 71
The combination of mechanistic and empirical models 71
Expert systems 72
The ‘RPR Adviser’ in Australia 72
Requirements for a global DSS for PR use 74
Creation of a database for PR reactivities 74
Creating a database of soils for PR use 74
Other requirements 75
Future developments 75
8. SECONDARY NUTRIENTS, MICRONUTRIENTS, LIMING EFFECT AND HAZARDOUS ELEMENTS ASSOCIATED
WITH PHOSPHATE ROCK USE 77
Secondary nutrients in phosphate rock 77
Micronutrients in phosphate rock 79
Liming effect associated with PR use 80
Hazardous elements in phosphate rock 82
v
9. WAYS OF IMPROVING THE AGRONOMIC EFFECTIVENESS OF PHOSPHATE ROCKS 85
Biological means 85
Phospho-composts 85
Inoculation of seedlings with endomycorrhizae 88
Use of ectomycorrhizae 90
Use of phosphate solubilizing micro-organisms 90
Use of plant genotypes 91
Chemical means 92
Partial acidulation of phosphate rock 92
Physical means 95
Compacted PR with water-soluble phosphate products 95
Dry mixtures of PR with water-soluble phosphate fertilizers 95
Phosphate rock elemental sulphur assemblages 95
10. ECONOMIC FACTORS IN THE ADOPTION AND UTILIZATION OF PHOSPHATE ROCKS 99
Possible adoption and use of phosphate rock by end users 100
Cost of production, transport and distribution 102
Economic considerations and policies to support PR adoption 104
Pricing policy 105
Organizational policy 105
Agricultural product markets 105
Risk protection 106
Research and extension policy 106
Case studies of PR exploitation and use 107
Marketing of indigenous phosphate rocks for direct application 109
Latin America 110
Asia 110
Sub-Saharan Africa 111
Economic criteria in PR adoption and use – a case study on Venezuela 111
Agronomic evaluation and domestic market potential 112
Economics of PAPR production 112
Pilot-plant evaluation test 114
PAPR quality 115
The Moron PAPR plant 115
Raw materials and products 115
11. LEGISLATION AND QUALITY CONTROL OF PHOSPHATE ROCKS FOR DIRECT APPLICATION 117
Current legislation on phosphate rock for direct application 117
Associated issues 118
Total P O content of PR 118
2 5
Solubility of phosphate rock 119
Expressing PR solubility 119
Free carbonate effect 120
Particle-size effect 121
Guidelines for legislation on DAPR 122
12. EPILOGUE 125
BIBLIOGRAPHY 127
vi
List of tables
1. World phosphate rock production, 1999 12
2. World consumption of direct application phosphate rock 12
3. World phosphate rock reserves and reserve base 13
4. World economic identifi ed phosphate concentrate resources 14
5. Solubility data on selected phosphate rock samples 21
6. Proposed classifi cation of PR for direct application by solubility and expected
initial response 23
7. Ranking system for some South American PRs by solubility and RAE 23
8. Chemical analysis and solubility in conventional reagents of selected
African PRs 28
9. Citrate soluble P of North Carolina PR as affected by particle size 29
10. Correlation coeffi cients between reactivity scales of seven PRs and crop yield 32
11. Spatial variability of PR samples within the same deposit 32
12. PR kinetics of isotopic exchange and solubility in water 33
13. Effects of incubating PRs on the characteristics of an Oxisol from Njole, Gabon 34
14. Results of a pot experiment with selected African PRs 36
15. Estimated RAE coeffi cients based on L values and P uptake from the pot
experiment 38
16. Changes with time of the estimated RAE coeffi cients for PRs applied to
a Madagascar Andosol 38
17. P uptake from PRs in a Madagascar Oxisol as infl uenced by soil water content 39
18. Correlation coeffi cients between P uptake and solubility tests 39
19. Crop yield and estimated RAEs from fi eld experiments in Burkina Faso 40
20. Yield of millet, groundnut, sorghum, cotton and maize with Tilemsi PR and
TSP, Mali, 1982–87 48
21. Yield of rice and maize with Mussoorie PR, SSP and a 1:1 mixture of Mussoorie
PR-SSP 51
22. Net returns on P fertilizers to fi nger millet and maize, and black gram grown
on the residual effect 52
23. Relative agronomic effectiveness of PRs for crops on a Typic Hapludult,
Pelaihari, Kalimantan 53
24. Comparison between a rehabilitated pasture using the PAPR-urea-Stylosanthes
capitata treatment and a traditional degraded pasture, Monagas State, Venezuela 56
25. AEI of phosphate fertilizers in a clayey Oxisol of central Brazil, based on
P uptake data over fi ve years with annual crops, followed by three years with
Andropogon pasture 56
vii
26. Relative agronomic effectiveness of various PRs with respect to CaCO as
3
a Ca source for maize 78
27. Chemical analysis of potentially hazardous elements in sedimentary phosphate
rocks 82
28. Nutrient content of organic waste materials and farmyard compost (dry basis
except for urine) 86
29. Effect of P sources on yield and P uptake for red gram and clusterbean 88
30. Matrix of costs and benefi ts associated with PR investments 108
31. Distribution of benefi ts for selected fertilizer strategies 109
32. Partially acidulated phosphate rocks based on various Venezuelan deposits 112
33. Current production capacity for P O at the Moron Complex 113
2 5
34. Pilot-plant evaluation results 115
35. Total P O , NAC-soluble P O , and CO :PO ratio of apatite in various
2 5 2 5 3 4
phosphate rocks 118
36. Citrate solubility of mixtures of North Carolina PR and sand 120
37. Citrate solubility of PRs containing various amounts of total P O 120
2 5
38. Solubility of PRs as measured by various chemical extractions 121
39. Solubility of ground and unground PRs 121
viii
List of fi gures
1. Economic and potentially economic phosphate deposits of the world 13
2. History of the discovery of world phosphate resources 15
3. Excess fl uorine francolites, correlation of moles of CO -2 with PO -3
3 4
per formula weight 18
4. Excess fl uorine francolites, variation in unit-cell a value with increasing
CO -2 for PO -3 substitution 18
3 4
5. Variation of CO contents in excess fl uorine francolites of various geological
2
ages 19
6. Relationship of the CaO/P O weight percent ratio to NAC-soluble P O ,
2 5 2 5
excess fl uorine francolites 20
7. Unit-cell a dimension versus NAC solubility of hydroxyl-fl uor-carbonate
apatites 20
8. NAC solubilities of sedimentary PRs from various countries 22
9. Flowsheet of the PR characterization process at the IFDC 24
10. Diagram showing the approximate modal analysis of phosphorite sample
No. 1 26
11. Kinetics of continuous dissolution of PRs with formic acid 31
12. Schematic representation of a crop response curve on adding PR to a severely
P-defi cient soil 44
13. Effect of partial acidulation of Mussoorie PR on yields of rice (soil pH 7.9)
and wheat (soil pH 6.0) 51
14. Relationship between plant P uptake and soil available P from TSP and
PR applied to acid soil 60
15. Relationship between dry-matter yield and Bray I-extractable P in soils
treated with PRs and TSP 61
16. Relationship between dry-matter yield of maize with different P sources
and Bray-I-P extracted from (a) acid sandy soil (pH 4.8) with low pH
buffering capacity and (b) acid soil (pH 5.2) with high P-fi xing capacity 62
17. Relationship between dry-matter yield of maize and (a) Bray-II-extractable P,
and (b) Mehlich-I-extractable P in soil treated with central Florida PR and TSP 63
18. Relationship between pasture yield and Olsen P values in soils treated with
Sechura PR and: (a) monocalcium phosphate, and (b) TSP 64
19. Relationship between P uptake by maize and Bray I-extractable P in soils
treated with TSP and North Carolina PR 65
20. Relationship between P uptake by maize and Pi-P (0.01 M CaCl ) in soils
2
treated with TSP and North Carolina PR 65
21. Pi-P with 0.01 M CaCl or 0.02 M KCl in soils treated with North Carolina PR 66
2