1. World Phosphorus Use Efficiency in Cereal Crops Guilherme Torres, Natasha Macnack, Bee Chim, Jeremiah Mullock, and William Raun Oklahoma State University, Plant and Soil Science Department World demand for phosphorus Phosphorus (P) is the second most limiting nutrient in crop systems and positively correlated with world food production. Batjes (1997) estimated that P deficiency can be found in 67% of the world land designated for crop production. Soil orders with potential P deficiency account for approximately 51% of the world soils (Brady and Weil, 2008) (Table 1). Based on current consumption, P reserves have been estimated to last from 100 years (Heffer et al., 2006) to 343 years (Roberts and Stewart, 2002). Table 1. Global distribution, potential macronutrient deficiency and nutrient toxicity associated with major soil orders†. †Adapted from Baligar et al. (2001). ‡ Brady and Weil, 2008. Objective Macro data was used to estimate mean and current global P use efficiency of cereal crops based on harvested area, fertilizer consumption, and production quantity. Global Phosphorus Use Efficiency 50 years (1961 to 2011) of world fertilizer P consumption, cereal harvested area, and production were obtained from the FAOSTAT database (2011) to estimate phosphorus use efficiency (PUE). Crops included maize, rice, wheat, sorghum, barley, millet, oats, rye, triticale and minor cereal crops. Cereal harvested area represents 55% of the total harvested area. Cereal P consumption = World P consumption x 55%. Figure 1: Global phosphorus fertilizer consumption and fertilizer phosphorus consumption by cereal crops from1961 to 2011. Grain P uptake and P removed from the soi l Cereal grain P uptake was calculated by multiplying the crop specific grain P content by the production of that given crop. It was assumed that 79.3% of the P found in the grain came from the soil and not the fertilizer. This value was computed from averaging data found in literature for P removal. PUE was calculated as: Cereal Production and P Consumption Over the last 50 years, world fertilizer P consumption has been increasing at a rate of 212,855 Mg yr -1 (Figure 1). There was a 346% increase in P fertilizer usage in 50 years. 50-year cereal production average was 1,704,807,560 Mg. Cereal production was 2,432,818,753 Mg in 2010 World cereal yield increased from 1.35 to 3.57 Mg ha -1 between 1961 and 2010. Phosphorus Use Efficiency 50 year and current world PUE for cereal crops was 15.7% and 19.2% PUE ranged from 12.0% in 1980 to 20.2% in 2008 (Figure 2). Figure 2: Historical estimates of world phosphorus use for cereal crops. Conclusion Global PUE is low (12-20%), indicating that P fertilization methods need to be improved in order to preserve the longevity of P reserves. References Baligar, V.C., N.K. Fageria, and Z.L. He. 2001. Nutrient use efficiency in plants. Commun. Soil Sci. Plant Anal. 32:921-950. Batjes, N.H. 1997. A world dataset of derived soil properties by FAO–UNESCO soil unit for global modelling. Soil Use Manage. 13:9-16. Brady, N.C., and R.R. Weil. 2008. The nature and properties of soils. 14 th ed. Prentice Hall, Upper Saddle River, NJ. Food and Agriculture Organization. 2011. FAOSTAT: Statistics database. [Online.] Available at http://faostat.fao.org/ (verified 9 Jul. 2012).http://faostat.fao.org/ Heffer, P., M.P.R. Prud'homme, B. Muirheid, and K.F. Isherwood. 2006. Phosphorus fertilisation: issues and outlook. Proc. Int. Fert. Soc. p. 1-32. Roberts, T., and W. Stewart. 2002. Inorganic phosphorus and potassium production and reserves. Better Crops 86:6-7.