PHOSPHATIC FERTILIZERS - BEHAVIOR IN SOILS AND MANAGEMENT.pptx

Phosphorus (P) was first discovered by Brandt in 1669. The word is derived from Greek, ‘phos’
meaning light and ‘phorus’ meaning bringing. Phosphorus is a major nutrient next to N and
plays an important role in plant physiology and biochemistry. It is involved in the building blocks,
a component of genetic material (nucleic acids) and an energy currency (ATP) of plants. However,
unlike N and K, P is taken up in smaller quantities by the plants. Further, P contrasts from N with
respect to its transformation in soil after fertilizer P is applied. While N is easily lost from the soil
system, P does not. It is mined from the finite natural resources and the supply is expected to
dwindle in the next 100–150 years. Thus, efficient use of the P fertilizers will play a key role in
sustaining crop production. understanding different forms of soil P and its transformation
in soils and the various factors influencing P availability is crucial. Followed by the role of P in plants,
its absorption and crop P requirements. Understanding Fertilizer P materials and the various
strategies that are needed for efficient use of P are important for field applications.

1. PHOSPHATIC FERTILIZERS - BEHAVIOR IN SOILS AND MANAGEMENT UNDER FIELD CONDITIONS SAC 502 SOIL FERTILITY AND FERTILIZER USE (2+1) K. Avinash I M.Sc. (Ag.) Soil Science Department Soil Science and Agricultural Chemistry Tamil Nadu Agricultural University

2. Phosphatic fertilizer % P = % P 2 O 5 x 0.43 Marketed as % P 2 O 5 content. % P 2 O 5 = % P x 2.29

3. Marketing Strategy Conventional use Why is P 2 O 5 is used to represent Phosphorous in fertilizers ? Source : (Lambers and Barrow, 2020)

4. History of Phosphatic fertilizers 1669 – Hennig Brandt – German alchemist accidently discovered P 1770 – Ghan and Scheele – Bone as source of P (Sweden) 1835 – James Murray – superphosphate of lime 1840 – Justus von Liebig – sulfuric acid + grounded bones to supply P to plants 1836-1838 – John Bennett Lawes used bone dust – turnips 1842 – Patent for superphosphate - Lawes 1867 – Rock phosphate discovered in U.S 1870s – TSP- produced in Germany 1955 – Introduction of Diammonium phosphate 1980s – TSP production peaked

5. 1669 – Hennig Brandt – German alchemist accidently discovered P 1770 – Ghan and Scheele – Bone as source of P (Sweden) 1835 – James Murray – superphosphate of lime 1840 – Justus von Liebig – sulfuric acid + grounded bones to supply P to plants 1836-1838 – John Bennett Lawes used bone dust – turnips 1842 – Patent for superphosphate - Lawes 1867 – Rock phosphate discovered in U.S 1870s – TSP- produced in Germany 1955 – Introduction of Diammonium phosphate 1980s – TSP production peaked

6. 1669 – Hennig Brandt – German alchemist accidently discovered P 1770 – Ghan and Scheele – Bone as source of P (Sweden) 1835 – James Murray – superphosphate of lime 1840 – Justus von Liebig – sulfuric acid + grounded bones to supply P to plants 1836-1838 – John Bennett Lawes used bone dust – turnips 1842 – Patent for superphosphate - Lawes 1867 – Rock phosphate discovered in U.S 1870s – TSP- produced in Germany 1955 – Introduction of Diammonium phosphate 1980s – TSP production peaked Source: Russel, D. A., & Williams, G. G. (1977).  History of Chemical Fertilizer Development1. Soil Science Society of America Journal, 41(2), 260.  doi:10.2136/sssaj1977.03615995004100020020x 

7. Water soluble Citric acid soluble Water and citric acid insoluble Suitable for neutral to alkaline soils Applied at time of sowing. Phosphorus → insoluble dicalcium phosphate (immediately after application – Granulated form prefered ) Water soluble phosphoric acid → un available iron aluminium phosphates (Acidic condition) Fertilizer P 2 O 5 % Single super phosphate 16-18 Double super phosphate 32 Triple super phosphate 46-48 Mono ammonium phosphate 20 Diammonium phosphate 46 P soluble in 2% citric acid or neutral normal ammonium acetate solution. P is present as dicalcium phosphate Ca 2 H 2 (PO 4 ) 2 / CaHPO 4 suitable for acid soils and lateritic soils low pH citrate soluble Phosphoric acid → monocalcium phosphate or water soluble phosphate Less chances of phosphate getting fixed as iron and aluminium phosphate. Fertilizer P 2 O 5 % Basic slags 14-18 Dicalcium phosphate 34-39 Rhenamia phosphate 23-26 Steamed bone meal 22

8. Citric acid soluble Water and citric acid insoluble Water soluble P soluble in 2% citric acid or neutral normal ammonium acetate solution. P is present as dicalcium phosphate Ca 2 H 2 (PO 4 ) 2 / CaHPO 4 suitable for acid soils and lateritic soils low pH citrate soluble Phosphoric acid → monocalcium phosphate or water soluble phosphate Less chances of phosphate getting fixed as iron and aluminium phosphate. Fertilizer P 2 O 5 % Basic slags 14-18 Dicalcium phosphate 34-39 Rhenamia phosphate 23-26 Steamed bone meal 22 Suitable for neutral to alkaline soils Applied at time of sowing. Phosphorus → insoluble dicalcium phosphate (immediately after application – Granulated form prefered ) Water soluble phosphoric acid → un available iron aluminium phosphates (Acidic condition) Fertilizer P 2 O 5 % Single super phosphate 16-18 Double super phosphate 32 Triple super phosphate 46-48 Mono ammonium phosphate 20 Diammonium phosphate 46 Contains insoluble phosphoric acid or tri calcium Phosphate (Ca 3 (PO 4 ) 2 Suited for acidic soils or organic soils . Large quantities of phosphatic fertilizers required to raise the soil fertility. Applied 1 month before sowing the crop - insoluble-P gets solubilized by the time of sowing of crop. Fertilizer P 2 O 5 % Rock phosphate 20-40 Raw bone meal 20-25 Steamed bone meal 22

9. Water and citric acid insoluble Citric acid soluble Water soluble Contains insoluble phosphoric acid or tri calcium Phosphate (Ca 3 (PO 4 ) 2 Suited for acidic soils or organic soils . Large quantities of phosphatic fertilizers required to raise the soil fertility. Applied 1 month before sowing the crop - insoluble-P gets solubilized by the time of sowing of crop. Fertilizer P 2 O 5 % Rock phosphate 20-40 Raw bone meal 20-25 Steamed bone meal 22 P soluble in 2% citric acid or neutral normal ammonium acetate solution. P is present as dicalcium phosphate Ca 2 H 2 (PO 4 ) 2 / CaHPO 4 suitable for acid soils and lateritic soils low pH citrate soluble Phosphoric acid → monocalcium phosphate or water soluble phosphate Less chances of phosphate getting fixed as iron and aluminium phosphate. Fertilizer P 2 O 5 % Basic slags 14-18 Dicalcium phosphate 34-39 Rhenamia phosphate 23-26 Steamed bone meal 22

10. P rimary raw material - P fertilizers. RP minerals are A patites Ca 10 (PO 4­ ) 6­ (X) 2 , where X is F - , OH - , or Cl - . Fluorapatite Ca 10 (PO 4­ ) 6­ F 2 is the most common RP. I mpurities - CO 3 , Na, Mg , and heavy metals ( Cd ). W ater insoluble, the citrate solubility varies 3–20% of total P. Finely ground RP can be applied directly to soil and reacts as: Ca 10 (PO 4­ ) 6­ F 2 + 12H 2 O → 10Ca 2+ + 6H 2 PO 4 - + 2F - + 12OH - Rock phosphate Increasing soil acidity - I ncrease dissolution of RP , soil acids - neutralize OH - produced and force the above reaction The solubility of RP (fluorapatite) increases as soil pH decreases. U se of RP restricted to very acidic soils in warm, moist climates characteristic of tropical regions. I mportant for permanent crops such as rubber, oil palm, and cocoa. Ground RP - Restoration of low P soils - Rates of 1–3 t/a. Ca 10 (PO 4­ ) 6­ F 2 + 12H 2 O → 10Ca 2+ + 6H 2 PO 4 - + 2F - + 12OH -

11. Rock phosphate Increasing soil acidity - I ncrease dissolution of RP , soil acids - neutralize OH - produced and force the above reaction The solubility of RP (fluorapatite) increases as soil pH decreases. U se of RP restricted to very acidic soils in warm, moist climates characteristic of tropical regions. I mportant for permanent crops such as rubber, oil palm, and cocoa. Ground RP - Restoration of low P soils - Rates of 1–3 t/a. Ca 10 (PO 4­ ) 6­ F 2 + 12H 2 O → 10Ca 2+ + 6H 2 PO 4 - + 2F - + 12OH - P rimary raw material - P fertilizers. RP minerals are A patites Ca 10 (PO 4­ ) 6­ (X) 2 , where X is F - , OH - , or Cl - . Fluorapatite Ca 10 (PO 4­ ) 6­ F 2 is the most common RP. I mpurities - CO 3 , Na, Mg , and heavy metals ( Cd ). W ater insoluble, the citrate solubility varies 3–20% of total P. Finely ground RP can be applied directly to soil and reacts as: Ca 10 (PO 4­ ) 6­ F 2 + 12H 2 O → 10Ca 2+ + 6H 2 PO 4 - + 2F - + 12OH - Rock phosphate

12. Source: U.S. Geological Survey, Mineral Commodity Summaries, January 2022 Increasing soil acidity - I ncrease dissolution of RP , soil acids - neutralize OH - produced and force the above reaction The solubility of RP (fluorapatite) increases as soil pH decreases. U se of RP restricted to very acidic soils in warm, moist climates characteristic of tropical regions. I mportant for permanent crops such as rubber, oil palm, and cocoa. Ground RP - Restoration of low P soils - Rates of 1–3 t/a. Ca 10 (PO 4­ ) 6­ F 2 + 12H 2 O → 10Ca 2+ + 6H 2 PO 4 - + 2F - + 12OH -

13. What is Peak Phosphorous ? Source: Cordell, D., & White, S. (2011).  Peak Phosphorus: Clarifying the Key Issues of a Vigorous Debate about Long-Term Phosphorus Security. Sustainability, 3(10), 2027–2049.  doi:10.3390/su3102027  Peak phosphorus is a concept to describe  the point in time when humanity reaches the maximum global production rate of phosphorus as an industrial and commercial raw material . IFDC (International fertilizer development center )estimates that there are sufficient phosphate rock concentrate reserves to produce fertilizer for the next 300-400 years .

14. P artially acidulated RP can I ncrease the water-soluble P content I mprove short-term crop response to RP. Partially acidulated RP is produced: By t reating RP with 10–20% of the quantity of H 3 PO 4 used for the manufacture of triple superphosphate or B y reacting it with 40–50% of the amount of H 2 SO 4 normally used in the production of single superphosphate. Rock phosphate Reacting RP with H 2 SO 4 produces phosphoric acid (H 3 PO 4 ), commonly referred to as green or wet-process acid , containing 17–24% P (39-55% P 2 O 5 ). A by-product of green acid production is gypsum (CaSO 4 ∙ 2H 2 O) that can be used as an S and Ca fertilizer, as an amendment for sodic soils, and for other industrial purposes. Ca 10 (PO 4­ ) 6­ F 2 + 10H 2 SO 4 + 20H 2 O → 6 H 3 PO 4 + 10CaSO 4 ∙ 2H 2 O + 2HF

15. P artially acidulated RP can I ncrease the water-soluble P content I mprove short-term crop response to RP. Partially acidulated RP is produced: By t reating RP with 10–20% of the quantity of H 3 PO 4 used for the manufacture of triple superphosphate or B y reacting it with 40–50% of the amount of H 2 SO 4 normally used in the production of single superphosphate. Rock phosphate Reacting RP with H 2 SO 4 produces phosphoric acid (H 3 PO 4 ), commonly referred to as green or wet-process acid , containing 17–24% P (39-55% P 2 O 5 ). A by-product of green acid production is gypsum (CaSO 4 ∙ 2H 2 O) that can be used as an S and Ca fertilizer, as an amendment for sodic soils, and for other industrial purposes. Ca 10 (PO 4­ ) 6­ F 2 + 10H 2 SO 4 + 20H 2 O → 6 H 3 PO 4 + 10CaSO 4 ∙ 2H 2 O + 2HF Heating RP in an electric furnace produces elemental P that is reacted with O 2 and H 2 O to form H 3 PO 4 , called white or furnace acid . White acid has a much higher degree of purity than green acid; however, high energy costs involved in manufacturing limits its use in agriculture. G reen acid - injected in soil or irrigation water (A lkaline and calcareous areas) almost all green acid is used to acidulate RP to make Ca and NH 4 phosphates. Common P fertilizers are produced from either acid- or heat-treated RP to increase water-soluble P.

16. Calcium phosphate Rock phosphate Heating RP in an electric furnace produces elemental P that is reacted with O 2 and H 2 O to form H 3 PO 4 , called white or furnace acid . White acid has a much higher degree of purity than green acid; however, high energy costs involved in manufacturing limits its use in agriculture. G reen acid - injected in soil or irrigation water (A lkaline and calcareous areas) almost all green acid is used to acidulate RP to make Ca and NH 4 phosphates. Common P fertilizers are produced from either acid- or heat-treated RP to increase water-soluble P. Reacting RP with H 2 SO 4 produces phosphoric acid (H 3 PO 4 ), commonly referred to as green or wet-process acid, containing 17–24% P (39-55% P 2 O 5 ). A by-product of green acid production is gypsum (CaSO 4 ∙ 2H 2 O) that can be used as an S and Ca fertilizer, as an amendment for sodic soils, and for other industrial purposes. Ca 10 (PO 4­ ) 6­ F 2 + 10H 2 SO 4 + 20H 2 O → 6 H 3 PO 4 + 10CaSO 4 ∙ 2H 2 O + 2HF SSP contains 7–9.5% P (16–22% P 2 O 5 ) and is an excellent source of S . Similar to production of green acid, SSP is produced by: The gypsum by-product is utilized as described before. TSP contains 17–23% P (44–52% P 2 O 5 ) and is produced by treating RP with H 3 PO 4 : Its high P content is an advantage because transportation, storage, and handling comprise a large fraction of total fertilizer cost. Ca 10 (PO 4­ ) 6­ F 2 + 7H 2 SO 4 + 14H 2 O → 3Ca(H 2 PO 4 ) 2 + 7CaSO 4 ∙ 2H 2 O + 2HF Ca 10 (PO 4­ ) 6­ F 2 + 14H 3 PO 4 → 10Ca(H 2 PO 4 ) 2 + 2HF

17. Calcium phosphate Rock phosphate Reacting RP with H 2 SO 4 produces phosphoric acid (H 3 PO 4 ), commonly referred to as green or wet-process acid, containing 17–24% P (39-55% P 2 O 5 ). A by-product of green acid production is gypsum (CaSO 4 ∙ 2H 2 O) that can be used as an S and Ca fertilizer, as an amendment for sodic soils, and for other industrial purposes. Ca 10 (PO 4­ ) 6­ F 2 + 10H 2 SO 4 + 20H 2 O → 6 H 3 PO 4 + 10CaSO 4 ∙ 2H 2 O + 2HF SSP contains 7–9.5% P (16–22% P 2 O 5 ) and is an excellent source of S . Similar to production of green acid, SSP is produced by: The gypsum by-product is utilized as described before. TSP contains 17–23% P (44–52% P 2 O 5 ) and is produced by treating RP with H 3 PO 4 : Its high P content is an advantage because transportation, storage, and handling comprise a large fraction of total fertilizer cost. Ca 10 (PO 4­ ) 6­ F 2 + 7H 2 SO 4 + 14H 2 O → 3Ca(H 2 PO 4 ) 2 + 7CaSO 4 ∙ 2H 2 O + 2HF Ca 10 (PO 4­ ) 6­ F 2 + 14H 3 PO 4 → 10Ca(H 2 PO 4 ) 2 + 2HF Source : Khasawneh et al., 1974, Soil Sci . Soc. Am. J., 38:446.)

18. Calcium phosphate SSP contains 7–9.5% P (16–22% P 2 O 5 ) and is an excellent source of S . Similar to production of green acid, SSP is produced by: The gypsum by-product is utilized as described before. TSP contains 17–23% P (44–52% P 2 O 5 ) and is produced by treating RP with H 3 PO 4 : Its high P content is an advantage because transportation, storage, and handling comprise a large fraction of total fertilizer cost. Ca 10 (PO 4­ ) 6­ F 2 + 7H 2 SO 4 + 14H 2 O → 3Ca(H 2 PO 4 ) 2 + 7CaSO 4 ∙ 2H 2 O + 2HF Ca 10 (PO 4­ ) 6­ F 2 + 14H 3 PO 4 → 10Ca(H 2 PO 4 ) 2 + 2HF Heating RP in an electric furnace produces elemental P that is reacted with O 2 and H 2 O to form H 3 PO 4 , called white or furnace acid . White acid has a much higher degree of purity than green acid; however, high energy costs involved in manufacturing limits its use in agriculture. G reen acid - injected in soil or irrigation water (A lkaline and calcareous areas) almost all green acid is used to acidulate RP to make Ca and NH 4 phosphates. Common P fertilizers are produced from either acid- or heat-treated RP to increase water-soluble P. Rock phosphate NH 4 phosphates are produced by reacting wet-proces s H 3 PO 4 with NH 3 Monoammonium phosphate Diammonium phosphate ( Both MAP and DAP are Granular W ater soluble fertilizers H igh nutrient content, R educes shipping, handling, and storage costs. NH 3 + H 3 PO 4 → NH 4 HPO 4 MAP - (11-52-0) NH 3 + H 3 PO 4 → (NH 4 ) 2 HPO 4 DAP - (18-46-0)

19. Ammonium phosphate NH 4 phosphates are produced by reacting wet-proces s H 3 PO 4 with NH 3 Both MAP and DAP are Granular W ater soluble fertilizers H igh nutrient content, R educes shipping, handling, and storage costs. NH 3 + H 3 PO 4 → NH 4 HPO 4 MAP - (11-52-0) NH 3 + H 3 PO 4 → (NH 4 ) 2 HPO 4 DAP - (18-46-0) SSP contains 7–9.5% P (16–22% P 2 O 5 ) and is an excellent source of S . Similar to production of green acid, SSP is produced by: The gypsum by-product is utilized as described before. TSP contains 17–23% P (44–52% P 2 O 5 ) and is produced by treating RP with H 3 PO 4 : Its high P content is an advantage because transportation, storage, and handling comprise a large fraction of total fertilizer cost. Ca 10 (PO 4­ ) 6­ F 2 + 7H 2 SO 4 + 14H 2 O → 3Ca(H 2 PO 4 ) 2 + 7CaSO 4 ∙ 2H 2 O + 2HF Ca 10 (PO 4­ ) 6­ F 2 + 14H 3 PO 4 → 10Ca(H 2 PO 4 ) 2 + 2HF Depending on rate, row or seed placement of DAP can cause seedling injury and inhibit root growth through NH 3 produced according to: H igh dissolution pH (pH 8.5) - NH 3 toxicity - calcareous or high pH soils. Seedling injury with MAP is observed in sensitive crops such as canola, flax, and other salt-sensitive crops. Low-reaction pH with MAP - increase micronutrient availability in calcareous soils (not consistent) (NH 4 ) 2 HPO 4 → 2NH 4 + + HPO 4 -2 (pH 8.52) 2NH 4 + + OH - → NH 3 + H 2 O

20. Ammonium phosphate Depending on rate, row or seed placement of DAP can cause seedling injury and inhibit root growth through NH 3 produced according to: H igh dissolution pH (pH 8.5) - NH 3 toxicity - calcareous or high pH soils. Seedling injury with MAP is observed in sensitive crops such as canola, flax, and other salt-sensitive crops. Low-reaction pH with MAP - increase micronutrient availability in calcareous soils (not consistent) (NH 4 ) 2 HPO 4 → 2NH 4 + + HPO 4 -2 (pH 8.52) 2NH 4 + + OH - → NH 3 + H 2 O NH 4 phosphates are produced by reacting wet-proces s H 3 PO 4 with NH 3 Both MAP and DAP are Granular W ater soluble fertilizers H igh nutrient content, R educes shipping, handling, and storage costs. NH 3 + H 3 PO 4 → NH 4 HPO 4 MAP - (11-52-0) NH 3 + H 3 PO 4 → (NH 4 ) 2 HPO 4 DAP - (18-46-0) M anufactured by reacting pyrophosphoric acid , H 4 P 2 O 7 , with NH 3 . Pyrophosphoric acid is produced from dehydration of wet-process acid . Polyphosphate is a term used to describe two or more orthophosphate ions combined together, with the loss of one H 2 O molecule per two H 2 PO 4 APP - liquid – 75% polyphosphate and 25% orthophosphate common APP grade is 10-34-0

21. Ammonium polyphosphate M anufactured by reacting pyrophosphoric acid, H 4 P 2 O 7 , with NH 3 . Pyrophosphoric acid is produced from dehydration of wet-process acid . Polyphosphate is a term used to describe two or more orthophosphate ions combined together, with the loss of one H 2 O molecule per two H 2 PO 4 APP - liquid – 75% polyphosphate and 25% orthophosphate common APP grade is 10-34-0 Depending on rate, row or seed placement of DAP can cause seedling injury and inhibit root growth through NH 3 produced according to: H igh dissolution pH (pH 8.5) - NH 3 toxicity - calcareous or high pH soils. Seedling injury with MAP is observed in sensitive crops such as canola, flax, and other salt-sensitive crops. Low-reaction pH with MAP - increase micronutrient availability in calcareous soils (not consistent) (NH 4 ) 2 HPO 4 → 2NH 4 + + HPO 4 -2 (pH 8.52) 2NH 4 + + OH - → NH 3 + H 2 O APP applied to soil, rapid chemical and biological hydrolysis of polyphosphate produces H 2 PO 4 . Phosphatase associated with plant roots and rhizosphere organisms are -biological hydrolysis of polyphosphates. Temperature, moisture, soil C, pH, and various conditions that encourage microbial and root growth favor phosphatase activity and polyphosphate hydrolysis. P olyphosphate hydrolysis increases – as soil temperature increases . Polyphosphates - effective as H 2 PO 4 - sources for crops.

22. APP applied to soil, rapid chemical and biological hydrolysis of polyphosphate produces H 2 PO 4 . Phosphatase associated with plant roots and rhizosphere organisms are -biological hydrolysis of polyphosphates. Temperature, moisture, soil C, pH, and various conditions that encourage microbial and root growth favor phosphatase activity and polyphosphate hydrolysis. P olyphosphate hydrolysis increases – as soil temperature increases . Polyphosphates - effective as H 2 PO 4 - sources for crops. Ammonium polyphosphate M anufactured by reacting pyrophosphoric acid, H 4 P 2 O 7 , with NH 3 . Pyrophosphoric acid is produced from dehydration of wet-process acid . Polyphosphate is a term used to describe two or more orthophosphate ions combined together, with the loss of one H 2 O molecule per two H 2 PO 4 APP - liquid – 75% polyphosphate and 25% orthophosphate common APP grade is 10-34-0 P roperty - chelation or sequestering reaction - micronutrient cations. APP can maintain 1–3% Zn in solution compared with only 0.05% Zn with H 2 PO 4 .

23. Ammonium polyphosphate APP applied to soil, rapid chemical and biological hydrolysis of polyphosphate produces H 2 PO 4 . Phosphatase associated with plant roots and rhizosphere organisms are -biological hydrolysis of polyphosphates. Temperature, moisture, soil C, pH, and various conditions that encourage microbial and root growth favor phosphatase activity and polyphosphate hydrolysis. P olyphosphate hydrolysis increases – as soil temperature increases . Polyphosphates - effective as H 2 PO 4 - sources for crops. P roperty - chelation or sequestering reaction - micronutrient cations. APP can maintain 1–3% Zn in solution compared with only 0.05% Zn with H 2 PO 4 . A granular fertilizer, urea ammonium phosphate (UAP), is produced by reacting urea with APP . The fertilizer grade is 28-12-0 (28-28-0), containing 20–40% polyphosphate. UAP can be easily blended with other granular fertilizers. Like DAP, seedling damage may occur when UAP is applied with the seed. Source : Tisdale, S.L et al., 1985

24. A granular fertilizer, urea ammonium phosphate (UAP), is produced by reacting urea with APP . The fertilizer grade is 28-12-0 (28-28-0), containing 20–40% polyphosphate. UAP can be easily blended with other granular fertilizers. Like DAP, seedling damage may occur when UAP is applied with the seed. Urea ammonium phosphate P roperty - chelation or sequestering reaction - micronutrient cations. APP can maintain 1–3% Zn in solution compared with only 0.05% Zn with H 2 PO 4 . Potassium phosphate products include KH 2 PO 4 and K 2 HPO 4 . W ater soluble commonly used in the horticulture industry. Their high P and K content - suited for solanaceous crops and many leafy vegetables sensitive to high levels of Cl - associated with KCl Their low-salt index reduces injury to germinating seeds and to young seedlings when placed close to the seed.

25. Potassium phosphate products include KH 2 PO 4 and K 2 HPO 4 . W ater soluble commonly used in the horticulture industry. Their high P and K content - suited for solanaceous crops and many leafy vegetables sensitive to high levels of Cl - associated with KCl Their low-salt index reduces injury to germinating seeds and to young seedlings when placed close to the seed. Potassium phosphate A granular fertilizer, urea ammonium phosphate (UAP), is produced by reacting urea with APP . The fertilizer grade is 28-12-0 (28-28-0), containing 20–40% polyphosphate. UAP can be easily blended with other granular fertilizers. Like DAP, seedling damage may occur when UAP is applied with the seed.

26. Ortho and poly - phosphates Polymer coated water-soluble fertilizers superabsorbent polymer coated slow-release P fertilizer Nano-P fertilizers may become sources of P fertilizers. The polymer-coated P fertilizers are expected to reduce P fixation and improve delivery to the plants. Potassium phosphate products include KH 2 PO 4 and K 2 HPO 4 . W ater soluble commonly used in the horticulture industry. Their high P and K content - suited for solanaceous crops and many leafy vegetables sensitive to high levels of Cl - associated with KCl Their low-salt index reduces injury to germinating seeds and to young seedlings when placed close to the seed. Source : Khasawneh et al., 1974

27. Polymer coated water-soluble fertilizers superabsorbent polymer coated slow-release P fertilizer Nano-P fertilizers may become sources of P fertilizers. The polymer-coated P fertilizers are expected to reduce P fixation and improve delivery to the plants. Novel P fertilizers

28. This is a by-product of the phosphoric acid plant where rock phosphate is reacted with sulfuric acid. Considerable amount of the material is produced and can be used as a P source. Phosphogypsum Polymer coated water-soluble fertilizers, superabsorbent polymer coated slow-release P fertilizer and nano-P fertilizers may become sources of P fertilizers. The polymer-coated P fertilizers are expected to reduce P fixation and improve delivery to the plants. However, it will depend on how effective these fertilizer sources are. This is a by-product of the steel industry and has low P content . Most of the P present is water and citrate-insoluble making it an ineffective P source . However, this material has a potential to be used as a liming agent for reclaiming acidic soils .

29. This is a by-product of the steel industry and has low P content . Most of the P present is water and citrate-insoluble making it an ineffective P source . However, this material has a potential to be used as a liming agent for reclaiming acidic soils . Basic slag This is a by-product of the phosphoric acid plant where rock phosphate is reacted with sulfuric acid. Considerable amount of the material is produced and can be used as a P source.

30. P fertilizer added to soil initially increases solution P subsequently solution P decreases through P adsorption to mineral surfaces, precipitation as Al/Fe- or Ca-P minerals, and immobilization by microbes. Some soil minerals may be dissolved by the concentrated P solution, resulting in the release of cations (Fe 3+ , Al 3+ , Mn 2+ , K 2+ , Ca 2+ , and Mg 2+ ) that react with P to form specific compounds, referred to as soil-fertilizer reaction products . Behaviour of P fertilizers in soil A cid soils - DCP and eventually AlPO 4 and/or FePO 4 precipitates from MCP. C alcareous soil - DCP and OCP are the dominant. R eaction pH for MAP 3.5 , for DAP 8.5 T he overall effect is temporary - volume of soil influenced by the P granule is small. Differences in availability of P sources to crops are small compared with differences in other P management factors such as P placement. Precipitation reactions are favored by high P concentrations . Adsorption reactions - most important at the periphery of the soil-fertilizer reaction zone, where P concentrations are lower . Although both precipitation and adsorption occur, precipitation accounts for most of the P being retained near the dissolving granule .

31. Behaviour of P fertilizers in soil A cid soils - DCP and eventually AlPO 4 and/or FePO 4 precipitates from MCP. C alcareous soil - DCP and OCP are the dominant. R eaction pH for MAP 3.5 , for DAP 8.5 T he overall effect is temporary - volume of soil influenced by the P granule is small. Differences in availability of P sources to crops are small compared with differences in other P management factors such as P placement. Precipitation reactions are favored by high P concentrations . Adsorption reactions - most important at the periphery of the soil-fertilizer reaction zone, where P concentrations are lower . Although both precipitation and adsorption occur, precipitation accounts for most of the P being retained near the dissolving granule . P fertilizer added to soil initially increases solution P subsequently solution P decreases through P adsorption to mineral surfaces, precipitation as Al/Fe- or Ca-P minerals, and immobilization by microbes. Some soil minerals may be dissolved by the concentrated P solution, resulting in the release of cations (Fe 3+ , Al 3+ , Mn 2+ , K 2+ , Ca 2+ , and Mg 2+ ) that react with P to form specific compounds, referred to as soil-fertilizer reaction products .

32. Behaviour of P fertilizers in soil Source : Khasawneh et al., 1974 A cid soils - DCP and eventually AlPO 4 and/or FePO 4 precipitates from MCP. C alcareous soil - DCP and OCP are the dominant. R eaction pH for MAP 3.5 , for DAP 8.5 T he overall effect is temporary - volume of soil influenced by the P granule is small. Differences in availability of P sources to crops are small compared with differences in other P management factors such as P placement. Precipitation reactions are favored by high P concentrations . Adsorption reactions - most important at the periphery of the soil-fertilizer reaction zone, where P concentrations are lower . Although both precipitation and adsorption occur, precipitation accounts for most of the P being retained near the dissolving granule . P diffusion away from TSP and DAP granules or an APP droplet in soil over 5 weeks Interaction of N with P Effect of Granule or Droplet Size Soil Moisture

33. Source : Khasawneh et al., 1974

34. Interaction of N with P Effect of Granule or Droplet Size Soil Moisture N promotes P uptake by plants by Increasing top and root growth, A ltering plant metabolism I ncreasing P solubility and availability. Increased root mass is largely responsible for increased crop uptake of P. NH 4 + fertilizers have a greater stimulating effect on P absorption than NO 3 - . Improved fertilizer P effectiveness can occur with P placed close to NH 4 + sources Since water-soluble P is rapidly converted to less-soluble P reaction products, decreasing contact between soil and fertilizer generally improves plant response to P fertilizer. Increasing granule or droplet size and/or band application of the fertilizer decreases soil fertilizer contact and maintains a higher solution P concentration for a longer time compared with broadcast P and/or fine particle size Interaction of N with P Effect of Granule or Droplet Size Soil Moisture N promotes P uptake by plants by Increasing top and root growth, A ltering plant metabolism I ncreasing P solubility and availability. Increased root mass is largely responsible for increased crop uptake of P. NH 4 + fertilizers have a greater stimulating effect on P absorption than NO 3 - . Improved fertilizer P effectiveness can occur with P placed close to NH 4 + sources Since water-soluble P is rapidly converted to less-soluble P reaction products, decreasing contact between soil and fertilizer generally improves plant response to P fertilizer. Increasing granule or droplet size and/or band application of the fertilizer decreases soil fertilizer contact and maintains a higher solution P concentration for a longer time compared with broadcast P and/or fine particle size

35. Effect of Granule or Droplet Size Soil Moisture Interaction of N with P Rate of Application Since water-soluble P is rapidly converted to less-soluble P reaction products, decreasing contact between soil and fertilizer generally improves plant response to P fertilizer. Increasing granule or droplet size and/or band application of the fertilizer decreases soil fertilizer contact and maintains a higher solution P concentration for a longer time compared with broadcast P and/or fine particle size Fertilizer P 2 O 5 % Rock phosphate 20-40 Raw bone meal 20-25 Steamed bone meal 22 N promotes P uptake by plants by Increasing top and root growth, A ltering plant metabolism I ncreasing P solubility and availability. Increased root mass is largely responsible for increased crop uptake of P. NH 4 + fertilizers have a greater stimulating effect on P absorption than NO 3 - . Improved fertilizer P effectiveness can occur with P placed close to NH 4 + sources Soil moisture content influences the effectiveness and availability of applied P. At field capacity, 50–80% of the water-soluble P can diffuse from the fertilizer granule within 24 hours. Even at 2–4% moisture, 20–50% of the water-soluble P moves out of the granule within the same time.

36. Soil Moisture Rate of Application Effect of Granule or Droplet Size Interaction of N with P Soil moisture content influences the effectiveness and availability of applied P. At field capacity, 50–80% of the water-soluble P can diffuse from the fertilizer granule within 24 hours. Even at 2–4% moisture, 20–50% of the water-soluble P moves out of the granule within the same time. Since water-soluble P is rapidly converted to less-soluble P reaction products, decreasing contact between soil and fertilizer generally improves plant response to P fertilizer. Increasing granule or droplet size and/or band application of the fertilizer decreases soil fertilizer contact and maintains a higher solution P concentration for a longer time compared with broadcast P and/or fine particle size Even though fertilizer P eventually forms less-soluble P compounds, the P concentration in solution increases with P application rate. With time the P concentration decreases as less-soluble P compounds precipitate. The duration of elevated solution P levels depends on the rate of P fertilizer applied, the method of P placement, the quantity of P removed by the crop, and soil properties that influence P availability.

37. Rate of Application Soil Moisture Effect of Granule or Droplet Size Even though fertilizer P eventually forms less-soluble P compounds, the P concentration in solution increases with P application rate. With time the P concentration decreases as less-soluble P compounds precipitate. The duration of elevated solution P levels depends on the rate of P fertilizer applied, the method of P placement, the quantity of P removed by the crop, and soil properties that influence P availability. Soil moisture content influences the effectiveness and availability of applied P. At field capacity, 50–80% of the water-soluble P can diffuse from the fertilizer granule within 24 hours. Even at 2–4% moisture, 20–50% of the water-soluble P moves out of the granule within the same time.

38. Fertilizer-P recommendations are presently done by the State Agricultural Universities on the basis of crop response . Of the fertilizer P applied, only 15–30% is taken up by the crop in the year of its application (Prasad and Power, 1997; Syers et al., 2008). Further, considering the fact that the entire fertilizer grade rock phosphate are imported in our country . PHOSPHORUS FERTILIZER MANAGEMENT

39. Interaction of N with P Effect of Granule or Droplet Size Soil Moisture Phosphorus sources Fertilizer P materials are available as water-soluble or as partially soluble and insoluble forms. Use of the water-soluble forms - are recommended in India - Alkaline and calcareous. Low water-soluble products (30 to 50) - effective for rice (Prasad and Dixit, 1976) Water-soluble sources are more important to short duration, fast growing crops with a restricted root-system. Rock phosphate - Acid soils . Since water-soluble P is rapidly converted to less-soluble P reaction products, decreasing contact between soil and fertilizer generally improves plant response to P fertilizer. Increasing granule or droplet size and/or band application of the fertilizer decreases soil fertilizer contact and maintains a higher solution P concentration for a longer time compared with broadcast P and/or fine particle size Use of a right source Right method of application Right time and dose N promotes P uptake by plants by Increasing top and root growth, A ltering plant metabolism I ncreasing P solubility and availability. Increased root mass is largely responsible for increased crop uptake of P. NH 4 + fertilizers have a greater stimulating effect on P absorption than NO 3 - . Improved fertilizer P effectiveness can occur with P placed close to NH 4 + sources Slow release fertilizer phosphorus Products Consist of DAP/MAP with a high charge-density polymer resulting in larger and longer-term plant availability of P). Dicarboxylic acid copolymer-coated fertilizer P product (Avail®) Crop may experience a short-fall in P supply due to slow-release of the P. Main use of such products would be in situations where P is at risk of loss by leaching such as the coarse-textured soils in high rainfall regions and soils prone to P fixation.

40. Interaction of N with P Effect of Granule or Droplet Size Soil Moisture Slow release fertilizer phosphorus Products Consist of DAP/MAP with a high charge-density polymer resulting in larger and longer-term plant availability of P). Dicarboxylic acid copolymer-coated fertilizer P product (Avail®) Crop may experience a short-fall in P supply due to slow-release of the P. Main use of such products would be in situations where P is at risk of loss by leaching such as the coarse-textured soils in high rainfall regions and soils prone to P fixation. Since water-soluble P is rapidly converted to less-soluble P reaction products, decreasing contact between soil and fertilizer generally improves plant response to P fertilizer. Increasing granule or droplet size and/or band application of the fertilizer decreases soil fertilizer contact and maintains a higher solution P concentration for a longer time compared with broadcast P and/or fine particle size Use of a right source Right method of application Right time and dose N promotes P uptake by plants by Increasing top and root growth, A ltering plant metabolism I ncreasing P solubility and availability. Increased root mass is largely responsible for increased crop uptake of P. NH 4 + fertilizers have a greater stimulating effect on P absorption than NO 3 - . Improved fertilizer P effectiveness can occur with P placed close to NH 4 + sources Fertilizer P gets fixed immediately after application to soils. Further, soil P concentration is low, besides this, diffusion is also slow. Diffusion coefficients values of H 2 PO 4 - range from 10-12 to 10-15 m 2 /s . At value 1 × 10-13 m 2 /s, movement of H 2 PO 4 - would be 0.13 mm/day. movement This very limited of phosphate ions So, it is necessary to have sufficient supply of readily-available P Phosphorus sources Fertilizer P materials are available as water-soluble or as partially soluble and insoluble forms. Use of the water-soluble forms - are recommended in India - Alkaline and calcareous. Low water-soluble products (30 to 50) - effective for rice (Prasad and Dixit, 1976) Water-soluble sources are more important to short duration, fast growing crops with a restricted root-system. Rock phosphate - Acid soils .

41. Interaction of N with P Effect of Granule or Droplet Size Soil Moisture Fertilizer P gets fixed immediately after application to soils. Further, soil P concentration is low, besides this, diffusion is also slow. Diffusion coefficients values of H 2 PO 4 - range from 10-12 to 10-15 m 2 /s . At value 1 × 10-13 m 2 /s, movement of H 2 PO 4 - would be 0.13 mm/day. movement This very limited of phosphate ions So, it is necessary to have sufficient supply of readily-available P Since water-soluble P is rapidly converted to less-soluble P reaction products, decreasing contact between soil and fertilizer generally improves plant response to P fertilizer. Increasing granule or droplet size and/or band application of the fertilizer decreases soil fertilizer contact and maintains a higher solution P concentration for a longer time compared with broadcast P and/or fine particle size Right method of application Right time and dose Use of a right source N promotes P uptake by plants by Increasing top and root growth, A ltering plant metabolism I ncreasing P solubility and availability. Increased root mass is largely responsible for increased crop uptake of P. NH 4 + fertilizers have a greater stimulating effect on P absorption than NO 3 - . Improved fertilizer P effectiveness can occur with P placed close to NH 4 + sources Greater yield response - banded P on low-P soils or soils with a greater ability to fix P. Concentrated band - contact with the soil and fixation is minimized. On soils with optimum to high levels of P, banding has less advantage and broadcast applications are adequate For rice (submerged) , Cereals - Broadcast method - immediately incorporated and plowed down, probability of root contact with the fertilizer is maximized. Placement/banding - Deep rooted and widely spaced crops, like cotton, tobacco. Slow release fertilizer phosphorus Products Consist of DAP/MAP with a high charge-density polymer resulting in larger and longer-term plant availability of P). Dicarboxylic acid copolymer-coated fertilizer P product (Avail®) Crop may experience a short-fall in P supply due to slow-release of the P. Main use of such products would be in situations where P is at risk of loss by leaching such as the coarse-textured soils in high rainfall regions and soils prone to P fixation.

42. Interaction of N with P Effect of Granule or Droplet Size Soil Moisture Fertilizer P gets fixed immediately after application to soils. Further, soil P concentration is low, besides this, diffusion is also slow. Diffusion coefficients values of H 2 PO 4 - range from 10-12 to 10-15 m 2 /s . At value 1 × 10-13 m 2 /s, movement of H 2 PO 4 - would be 0.13 mm/day. movement This very limited of phosphate ions So, it is necessary to have sufficient supply of readily-available P Right method of application Right time and dose Use of a right source N promotes P uptake by plants by Increasing top and root growth, A ltering plant metabolism I ncreasing P solubility and availability. Increased root mass is largely responsible for increased crop uptake of P. NH 4 + fertilizers have a greater stimulating effect on P absorption than NO 3 - . Improved fertilizer P effectiveness can occur with P placed close to NH 4 + sources Greater yield response - banded P on low-P soils or soils with a greater ability to fix P. Concentrated band - contact with the soil and fixation is minimized. On soils with optimum to high levels of P, banding has less advantage and broadcast applications are adequate For rice (submerged) , Cereals - Broadcast method - immediately incorporated and plowed down, probability of root contact with the fertilizer is maximized. Placement/banding - Deep rooted and widely spaced crops, like cotton, tobacco. Application of recommended rate - Efficient Timing of application is important - matching P supply with crop demand. Fixation of soil P increases with time of contact between soluble P and soil particles. Applying - Before planting - soils with high P-fixing capacities. P requirement is high in initially and crop-root growth Application done based on soil moisture.

43. Right time and dose Right method of application Use of a right source Fertilizer P 2 O 5 % Rock phosphate 20-40 Raw bone meal 20-25 Steamed bone meal 22 Application of recommended rate - Efficient Timing of application is important - matching P supply with crop demand. Fixation of soil P increases with time of contact between soluble P and soil particles. Applying - Before planting - soils with high P-fixing capacities. P requirement is high in initially and crop-root growth Application done based on soil moisture. Greater yield response - banded P on low-P soils or soils with a greater ability to fix P. Concentrated band - contact with the soil and fixation is minimized. On soils with optimum to high levels of P, banding has less advantage and broadcast applications are adequate For rice (submerged) , Cereals - Broadcast method - immediately incorporated and plowed down, probability of root contact with the fertilizer is maximized. Placement/banding - Deep rooted and widely spaced crops, like cotton, tobacco.

44. References Amarasinghe , Thilini , Chamalki Madhusha , Imalka Munaweera, and Nilwala Kottegoda . 2022. "Review on mechanisms of phosphate solubilization in rock phosphate fertilizer." Communications in Soil Science and Plant Analysis 53 (8):944-960. Bhattacharya, Amitav. 2019. "Changing environmental condition and phosphorus-use efficiency in plants." Changing climate and resource use efficiency in plants :241-305. Blaise, Desouza , Venugopalan , Mv, Singh, and Geeta. 2018. "Phosphorus Management. ." Cordell, Dana, and Stuart White. 2011. "Peak phosphorus: clarifying the key issues of a vigorous debate about long-term phosphorus security." Sustainability 3 (10):2027-2049. Delgado, Antonio, Miguel Quemada, and Francisco J Villalobos. 2016. "Fertilizers." Principles of agronomy for sustainable agriculture :321-339. Foth , HD. 1990. Fundamentals of soil science . 8 ed: John Wiley & Sons, Inc. Hedley, Mike, and Mike McLaughlin. 2005. "Reactions of phosphate fertilizers and by‐products in soils." Phosphorus: agriculture and the environment 46:181-252. Khasawneh , FE, EC Sample, and Isao Hashimoto. 1974. "Reactions of ammonium ortho‐and polyphosphate fertilizers in soil: I. Mobility of phosphorus." Soil Science Society of America Journal 38 (3):446-451. Lambers, Hans, and NJ Barrow. 2020. Pervasive use of P 2 O 5, K 2 O, CaO , MgO, and basic cations, none of which exist in soil. Springer. Lindsay, Willard L, Paul LG Vlek , and Sen H Chien. 1989. "Phosphate minerals." Minerals in soil environments 1:1089-1130. Michele, ME. 2022. "US Geological Survey, Mineral Commodity Summaries, January 2022." Roberts, Terry L. 2019. "Phosphorus: past history and contributions to the global food supply." Better Crops Plant Food 103 (1):6-8.

45. References Russel, Darrell A, and Gerald G Williams. 1977. "History of chemical fertilizer development." Soil Science Society of America Journal 41 (2):260-265. Saeid , A, M Labuda , K Chojnacka , and H Górecki. 2014. " Valorization of bones to liquid phosphorus fertilizer by microbial solubilization." Waste and Biomass Valorization 5:265-272. Sample, EC, RJ Soper, and GJ Racz . 1980. "Reactions of phosphate fertilizers in soils." The role of phosphorus in agriculture :263-310. Samreen, Sayma, and Sharba Kausar. 2019. "Phosphorus Fertilizer: The original and commercial sources." Phosphorus-recovery and Recycling :1-14. doi: http://dx.doi.org/10.5772/intechopen.82240 . Tisdale, S.L., Nelson, W.L. and Beaton, J.D. (1985) Soil Fertility and Fertilizers. 4th Edition, Macmillan Publishing Company, New York. Wisniak , Jaime. 2005. "Phosphorus-from discovery to commodity." https://extension.umn.edu/phosphorus-and-potassium/understanding-phosphorus-fertilizers https://www.indorama.com/products/phosphate-fertilizers https://ifdc.org/2010/09/22/ifdc-report-indicates-adequate-phosphorus-resources-available-to-meet-global-food-demands/ https://pubs.usgs.gov/periodicals/mcs2022/mcs2022-phosphate.pdf

46. Thank You