13 th esa congress25-29 august 2014, debrecen, hungary a delgado phosphorus fertilization: a global...

13th ESA Congress25-29 August 2014, Debrecen, Hungary A Delgado

PHOSPHORUS FERTILIZATION: A GLOBAL CONSTRAINT IN THE FUTURE?

Antonio DelgadoUniversity of Seville

13th ESA Congress25-29 August 2014, Debrecen, Hungary A Delgado13th ESA Congress25-29 August 2014, Debrecen, Hungary

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 Delgado13th ESA Congress25-29 August 2014, Debrecen, Hungary

Essential element for life

P source for fertilizers is phosphate rock (PR)

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


Expected negative P balance in soils in developed countries

Trends in the use of P

Ryan et al. 2012


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

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)


Production and consumption of P

China, Morocco and USA produce around 70 % of phosphate rock

Ryan et al. 2012

Ryan et al. 2012

China, India, and Brazil consume around 65 % of total P


STRATEGIC RESOURCE

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 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


Y = 79,1 - 0,039 x

Total P ( mg P / kg )400 500 600 700 800 900 1000 1100 1200

Org

anic

P to

Tot

al P

ratio

(%)

20

30

40

50

60

70

80

R2 = 0,43P < 0.001

% o

f T

ota

l in

org

an

ic P

0

10

20

30

40

50

60

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


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)


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 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


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 positiveThe role of manure as P source is determined by dominant P forms


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

0

5

10

15

20

25

9 14 23 31

Olsen P (mg/kg)

P u

ptak

e (k

g P

/ha)

P applied

P recovery


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)


Interaction with other nutrientsZ

n i

n p

lan

t (m

g k

g-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

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

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


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

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 coatingFoliar sprays

Strategy is not new (since 70’s); however it is gaining attention after P crisis


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


Efficient P recycling strategies at different scales

Europe depend on external P resources; use efficiency at a continental scale is low

00.5

11.5

22.5

33.5

44.5

5

kg P

per

hab

itan

t an

d y

ear

Ott & Rechberger (2012)

P surplus in agricultural soils Large 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)


Cordell et al. 2009

Recycling at smaller scales?


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 soilsMore efficient P fertilization schemes:

o More accurate P availability indexo New fertilizer productso New application methods


13th ESA Congress25-29 August 2014, Debrecen, Hungary A Delgado

PHOSPHORUS FERTILIZATION: A GLOBAL CONSTRAINT IN THE FUTURE?

Antonio DelgadoUniversity of Seville

13 th esa congress25-29 august 2014, debrecen, hungary a delgado phosphorus fertilization: a global...

Documents

available p

p geochemistry

problem of p

unpublishedorganic p

p olsen

unpublishedsoil p

p status

p crisisvaccari