The document discusses the history of understanding phosphorus use in agriculture and its importance as a nutrient for plant growth. It examines world phosphate reserves and how applied phosphorus interacts with soil properties, becoming either available or unavailable to plants over time. Several strategies are presented for improving phosphorus use efficiency in soils and maximizing the availability of phosphorus for crop uptake.

3. Hinning Brand is boiling Urine Krafft German Chemist

4. Robert Boyle

5. Phosphorus extraction from Phosphate Rock John Bennett Lawes Rothemsted Experimental Station

7. waxy white (yellow cut), red (granules center left, chunk center right), and violet phosphorus

8. 2. World Phosphate Reserves 18,000,000 World total (rounded) 1,200,000 77,000 260,000 25,000 6,600,000 100,000 90,000 180,000 900,000 5,700,000 200,000 50,000 1,500,000 100,000 30,000 100,000 800,000 United States Australia Brazil Canada China Egypt India Israel Jordan Morocco Russia Senegal South Africa Syria Togo Tunisia Other Countries (including Pakistan 7.45 million metric tons) Reserves (*000 Metric tons) Country

11. 4. When fertilizer is applied to soil, it dissolves in water and gives phosphorus ions, which have negative charges while the clay mineral in soil have also negative charges then how it is adsorbed and retained in soil?

12. Schematic diagram of the phosphate cycle

14. How Can organically complexed metals affect P adsorption? P is complexed with OM through metal bridges? OM interferes with Ca-P and metal oxide precipitation by coating the calcite surfaces?

23. Roots Interception

26. Percentage recovery of three amounts of applied P at two levels of Olsen P, sandy clay loam soil, saxmundham Data are the mean of two 4-year rotations, 1969-1972 and 1970-73. Rotation: sugar beet, barley, potatoes, barley Total P applied in 4 years was 55, 110 and 165 kg P/ha. Ditto Formula 50 39 Ditto Fromula 4 24 82.2 63.8 165 Ditto Formula 72 52 Ditto Formula 4 31 79.4 57.2 110 46.9/55 *100 140 85 (46.9-23.3)/55 *100 3 43 77.0 46.9 55 75.2 23.3 0 Formula used % recovery by the balance method Formula used % recovery by the difference method P uptake in 4 years (kg p/ha) 33 4 33 4 33 4 P applied (kg/ha) Olsen P (mg/kg)

27. P offtake 1856-2001 by arable crops growing on plots that had received no P or a total of 1410 kg/ha from 1865-1901 and none since, Exhaustion Land, Rothamsted 1 P in winter wheat and spring barley grain plus straw and in potato tubers. 2 Except 1902-1940 when no N was applied. 531 (56-2001) 170 (02-48) 308 (56-1948) 138 (56-01) Total of the variable period 5.45 4.18 42 1115 (56-2001) 9.63 96 Wheat 10 92-2001 4.38 4.06 65 8.44 135 Barley 16 1976-91 5.08 4.46 116 9.54 248 Barley 26 1949-74 4.1 4.9 39 307 (02-48) 9 72 Barley 9 1941-48 2.66 3.36 131 636 (56-1948) 6.02 235 Barley 39 1902-40 4.77 1.73 45 329 (56-01) 6.5 169 Potatoes 26 76-1901 3.35 4.65 93 8 160 wheat 20 1856-75 Per year Total Per year Total Difference in annual P offtake Plot 7 (N)2 p offtake Total of the variable period Plot 7 (NPK)2 p offtake Cropping No of Years Period

28. Cumulative recovery by arable crops of P applied between 1856 and 1901, Exhaustion Land, Rothamsted. 1115/1410 *100 636/1410 *100 329/1410 *100 Formula 41 23 14 Difference Method (1115-531)/1410 *100 79 1115 160+169+235+72+248+135+96 W+P+B+B+B+B+W 1856-2001 (636-308)/1410 *100 45 636 160+169+235+72 W+P+Barley+Barley (B) 1856-1948 (329-138)/1410 *100 23 329 160+169 Wheat (W)+ Potato (P) 1856-1901 Formula Balance Method Kg/ha Kg/ha Recovery (%) Total P offtake Individual offtake by crop Crops Period

29. Percentage recovery by the balance method of the residue of P applied between 1856 and 1901that remained in the soil in 1901 and 1948, Exhaustion Land, Rothamsted. Formula 62 28 Recovery (%) 479*100/774 248+35+96= 479 1410-479 774 1949-2001 307*100/1081 235+72= 307 1410-307 1081 1902-1948 Formula & Recovery % P offtake (kg/ha) Formula Used P residue (kg/ha) Period

30. Immediately High Low Very low Accessible Accessibility Accessibility Accessibility In Solution Readily extractable Low extractability Very low extractability Immediately Readily low Very low Available available availability availability Soil Solution Surface- adsorbed P Strongly-bonded Or Absorbed P Very strongly-bonded Or inaccessible or mineral Or precipitated P 8. Conceptual diagram for the forms of inorganic P in soils categorized in terms of accessibility, extractability and plant availability.

34. Thanks