Phosphorus (P) is critically needed to improve the soil fertility for crop production in large areas of developing countries. The high cost of conventional, water-soluble P fertilizers constrains their use by resource-poor farmers. Finely ground phosphate rock (PR) has been tested and used as a direct application fertilizer on tropical acid soils as a low-cost alternative where indigenous deposits of PR are located. However, direct application of PR with low reactivity or with inappropriate soil/crop combinations does not always give satisfactory results. Partial acidulation of PR (PAPR) or compaction with triple superphosphate (PR + TSP) or single superphosphate (PR + SSP) represent technologies that can be used to produce highly effective P fertilizers from those indigenous deposits. Numerous field trials conducted by IFDC in Asia, sub-Saharan Africa, and Latin America have demonstrated that PAPR at 40-50% acidulation with H2SO4 or at 20% with H3PO4 approaches the effectiveness of SSP or TSP in certain tropical soils and crops. This paper discusses how the agronomic effectiveness of PAPR is affected by mineralogical composition and reactivity of PR used and by soil properties and soil reactions. The paper also indicates that if a PR has high Fe2O3 + Al2O3 content, it may not be suitable for PAPR processing because of the reversion of water-soluble P to water-insoluble P during the PAPR manufacturing process. Under these conditions, compaction of PR with water-soluble P fertilizers (e.g. SSP, TSP) at P ratio of approximately 50:50 can be agronomically and economically attractive for utilizing the indigenous PRs in developing countries.
This is a preview of subscription content, access via your institution.
Buy single article
Instant access to the full article PDF.
Price includes VAT (USA)
Tax calculation will be finalised during checkout.
Bationo A, Mughogho SK and Mokwunye AU (1986) Agronomic Evaluation of Phosphate Fertilizers in Tropical Africa. In: Management of Nitrogen and Phosphorus Fertilizers in Sub-Saharan Africa, pp 283–318. Martinus Nijhoff Publishers, Dordrecht, The Netherlands
Chien SH (1979) Dissolution of phosphate rock in acid soils as influenced by nitrogen and potassium fertilizers. Soil Sci 127: 371–376
Chien SH and Hammond LL (1988) Agronomic Evaluation of Partially Acidulated Phosphate Rocks in the Tropics: IFDC Experience. IFDC - P-7. International Fertilizer Development Center, Muscle Shoals, AL
Chien SH and Hammond LL (1989) Agronomic effectiveness of partially acidulated phosphate rock as influenced by soil phosphorusfixing capacity. Plant Soil 120: 159–164
Chien SH, Sompongse D, Henao J. and Hellums DT (1987) Greenhouse evaluation of phosphorus availability from compacted phosphate rocks with urea or with urea and triple superphosphate. Fert Res 14: 245–256
Engelstad OP and Hellums DT (1993) Water solubility of phosphate fertilizers: agronomic aspects - a literature review. IFDC-P-17. International Fertilizer Development Center, Muscle Shoals, AL
Hagin J and Katz S (1985) Effectiveness of partially acidulated phosphate rock as a P source to plants in calcareous soils. Fert Res 8: 117–128
Hammond LL, Chien SH and Mokwunye AU (1986) Agronomic value of unacidulated and partially acidulated phosphate rocks indigenous to the tropics. Adv Agron 40: 89–140
Hammond LL, Chien SH and Polo JR (1980) Phosphorus availability from partial acidulation of two phosphate rocks. Fert Res 1: 37–49
Hammond LL, Chien SH, Roy AH and Mokwunye AU (1989) Solubility and agronomic effectiveness of partially acidulated phosphate rocks as influenced by their iron and aluminum oxide content. Fert Res 19: 93–98
Hams DJ (1985) Comparison of Phosphate Rock Sources in Two Benchmark Soils. In: Silva JA (ed) Soil-Based Agrotechnology Transfer, pp 117–125. University of Hawaii, Honolulu, HI
IFDC (1988) Annual report. International Fertilizer Development Center, Muscle Shoals, AL
Kpomblekou K (1989) Characteristics and Agronomic Effectiveness of Phosphate Fertilizers Derived From Togo Rock. M.S. Thesis, Tuskegee University, Unpublished
Kpomblekou K, Chien SH, Henao J and Hill WA (1991) Greenhouse evaluation of phosphate fertilizers produced from Togo phosphate rock. Commun Soil Sci Plant Anal 22: 63–73
Lupin MS and Le ND (1983) Compaction, An Alternative Approach for Granular Fertilizers. IFDC - T-25. International Fertilizer Development Center, Muscle Shoals, AL
McLean EO and Logan TJ (1970) Sources of phosphorus for plants grown in soils of differing phosphorus fixation tendencies. Soil Sci Soc Am J 34: 907–911
Menon RG and Chien SH (1990) Phosphorus availability to maize from partially acidulated phosphate rocks and phosphate rocks compacted with triple superphosphate. Plant Soil 127: 123–128
Mokwunye AU and Chien SH (1980) Reactions of partially acidulated phosphate rock with soils from the tropics. Soil Sci Soc Am J 44: 477–482
Schultz JJ (1986) Sulfuric Acid-Based Partially Acidulated Phosphate Rock: Its Production, Cost, and Use. IFDC - T-31. International Fertilizer Development Center, Muscle Shoals, AL
About this article
Cite this article
Chien, S.H., Menon, R.G. Agronomic evaluation of modified phosphate rock products. Fertilizer Research 41, 197–209 (1995). https://doi.org/10.1007/BF00748309
- agronomic effectiveness
- compacted phosphate rock with superphosphate
- partially acidulated phosphate rock