1. 13 th ESA Congress25-29 August 2014, Debrecen, Hungary A Delgado PHOSPHORUS FERTILIZATION: A GLOBAL CONSTRAINT IN THE FUTURE? Antonio Delgado University of Seville 13 th ESA Congress25-29 August 2014, Debrecen, Hungary A Delgado 13 th ESA Congress25-29 August 2014, Debrecen, Hungary

2. Soils are inherently deficient in P P deficiency in soil solved with progressive strategy of soil enrichment Some key points on P fertilization P reactions implies low efficiencies of fertilizer A Delgado 13 th ESA Congress25-29 August 2014, Debrecen, Hungary Essential element for life P source for fertilizers is phosphate rock (PR)

3. P balance in the World (McDonald et al. 2011)  Excessive P supply in rich countries  Deficitary supply in many poor countries  At a global scale, P is an agronomic problem affecting food production A Delgado 13 th ESA Congress25-29 August 2014, Debrecen, Hungary

4. Expected negative P balance in soils in developed countries Trends in the use of P Ryan et al. 2012 A Delgado 13 th ESA Congress25-29 August 2014, Debrecen, Hungary

5. When does people begin to be worried (frighten?) with P? 2008 was the year: the “P crisis” Vaccari, 2009 Cutting Chinese exports Decrease in P rock production in USA

6. P comes from mining (phosphate rock) a NON-RENEWABLE RESOURCE Modeled P peak production (Cordell et al. 2009) Progressive depletion of known reserves Model for evolution of prices of P rock (Van Vuuren et al. 2010) A Delgado 13 th ESA Congress25-29 August 2014, Debrecen, Hungary

7. Production and consumption of P China, Morocco and USA produce around 70 % of phosphate rock Ryan et al. 2012 China, India, and Brazil consume around 65 % of total P A Delgado 13 th ESA Congress25-29 August 2014, Debrecen, Hungary STRATEGIC RESOURCE

8. Phosphorus scarcity linked to food security is emerging as one of 21st Century’s key global environmental challenges (Cordell and Neset, 2014) A statement regarding “the problem of P”: And only one recourse: The main challenge now for scientific community is how to use P resources more efficiently. A Delgado 13 th ESA Congress25-29 August 2014, Debrecen, Hungary

9. A relevant portion of global P reserves is in agricultural soils (“the P legacy”)  Accurate estimation of plant-available P in soil  Increased ability of plants to use soil P  Precise P fertilization schemes  More efficient P fertilizers  More efficient recycling strategies Strategies for efficient P resource management must consider: Fertilization schemes have not significantly change during the last decades; Innovation is possible A Delgado 13 th ESA Congress25-29 August 2014, Debrecen, Hungary

10. Adsorbed + soluble phosphates accounts for less than 25 % of total inorganic P, (Delgado, unpublished) Organic P can be the dominant form (Delgado, unpublished) Soil P: a small fraction of total P in soil is readily available to plants Can this large P reserve in soils be mobilized by plants?: biological resource manipulation A Delgado 13 th ESA Congress25-29 August 2014, Debrecen, Hungary

11. Rhizosphere manipulation Trichoderma asperellum T34 Use of free-living microorganisms able to provide additional benefits T34 increase P uptake (Delgado, unpublished) Bacillus subtilis increase P uptake from insoluble Ca phosphates (Delgado, unpublished) A Delgado 13 th ESA Congress25-29 August 2014, Debrecen, Hungary

12. Precise P fertilization schemes: looking for the maximum efficiency  Knowledge of P supply potential of soil  Adapted to P geochemistry and P status in soil  Adapted to other agricultural practices  Interaction with other nutrients A Delgado 13 th ESA Congress25-29 August 2014, Debrecen, Hungary

13. A simple experiment: 1 mg of P Olsen in growing media (34 soils); plants extract between 0.03 and 2.5 mg P!! Are P availability indexes accurate for fertilization schemes? (Modified from Sánchez et al. 2014)(Delgado et al., 2010) Other evidences of the lack of accuracy A Delgado 13 th ESA Congress25-29 August 2014, Debrecen, Hungary

14. Fertilization adapted to P geochemistry in soils Soils with high adsorption capacity  Banded application  Blocking P sorption sites Soils with precipitation of metal phosphates  Splitting of P rate  Slow release P fertilizers  Organic matter Soils with low P retention capacity  Splitting  Slow P release fertilizers The combined application of P and organic matter is positive The role of manure as P source is determined by dominant P forms A Delgado 13 th ESA Congress25-29 August 2014, Debrecen, Hungary

15. Fertilization adapted to P sorption capacity and soil P status  Efficiency of P fertilizer is low (10-25%)  Assessed using the ‘balance’ method it is higher (even > 80 %)  Efficiency decrease in high-fixing soils and in P-poor soils Critical value 23 for “full recovery” Rothamsted (Syers et al. 2010) Wheat yield (t/ha) 7.1 7.8 7.9 7.9 A Delgado 13 th ESA Congress25-29 August 2014, Debrecen, Hungary

16. P fertilization adapted to other agricultural practices Tillage  Incorporation to soil required  Deep banded for no-till Irrigation  Possibility of fertigation  Different P threshold levels in soils  Efficient use of soil P Amendments  Efficient sources of P  Enhance availability of applied P Foliar sprays Possibility of foliar fertilization (“feeding the plant”, not the soils) A Delgado 13 th ESA Congress25-29 August 2014, Debrecen, Hungary

17. Interaction with other nutrients Zn in plant (mg kg -1 ) Interaction with Zn (wheat, del Campillo et al. unpublished) High P rates increased incidence of Fe deficiency chlorosis (olive, Sánchez-Rodriguez et al. 2013)  P fertilization can affect the uptake of micronutrients  Micronutrient-enriched P fertilizers can have negative effects on P nutrition

18. New fertilizer products  Slow-release P fertilizers  Products dissolved under rhizospheric conditions  Fertilizers able to block adsorption sites  Biofertilizers Antonini et al. 2012 Products dissolved under rhizospheric conditions:  Metal phosphates (e.g. struvite)  Organo-metallic compounds Struvite

19. New application schemes to soil Banding (surface or deep)  Not always effective  It makes more complex P fertility management  Required if fertilizer incorporation to soil is not possible with tillage A Delgado 13 th ESA Congress25-29 August 2014, Debrecen, Hungary

20. Ben-Gal and Dudley, 2003 Fertigation  Higher P concentrations in the bulb  Decreased P precipitation rate High splitting, location near roots, water regime contribute to increased efficiencies

21. Other alternatives for P application are required  P balance for soils above threshold values to maintain soil P legacy Soil application with a build-up strategy is not the solution in  In high P-fixing soils with low P-status  P-poor soils under a perspective of increasing prices Why not “feeding the plants” instead “feeding the soil” (Withers et al. 2014) Seed coating Foliar sprays Strategy is not new (since 70’s); however it is gaining attention after P crisis A Delgado 13 th ESA Congress25-29 August 2014, Debrecen, Hungary

22. McBeath et al. 2011 Efficiency of foliar P in wheat soil Effectiveness depend on: soil P status, soil water status, crop type, fertiliser formulation and climatic conditions (Noack et al. 2010)  Basal application required  Seldom offset fertilization costs. (Mallarino et al. 2001) Unclear results with foliar sprays Economy can change with:  Increasing prices of P fertilizer  Combination with agrochemical treatments A Delgado 13 th ESA Congress25-29 August 2014, Debrecen, Hungary

23. Efficient P recycling strategies at different scales Europe depend on external P resources; use efficiency at a continental scale is low Ott & Rechberger (2012) P surplus in agricultural soilsLarge portion of P is lost Required:  Mass flow analysis  Recycling of P-rich wastes  Improved wastewater treatment  Recycling at farm scales Too much P in diet Recycling can provide different P sources: struvite, ashes, compost, or soluble P forms obtained from wastes (e.g. MAP) A Delgado 13 th ESA Congress25-29 August 2014, Debrecen, Hungary

24. Cordell et al. 2009 Recycling at smaller scales? A Delgado 13 th ESA Congress25-29 August 2014, Debrecen, Hungary

25. Conclusions  Phosphorus is a finite non-renewable and strategic resource  European agriculture relies on external P supply  Increased P recycling is required  More efficient use in agriculture is required Rational use of P legacy in soils More efficient P fertilization schemes: o More accurate P availability index o New fertilizer products o New application methods A Delgado 13 th ESA Congress25-29 August 2014, Debrecen, Hungary

26. A Delgado PHOSPHORUS FERTILIZATION: A GLOBAL CONSTRAINT IN THE FUTURE? Antonio Delgado University of Seville