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
A Delgado13th ESA Congress25-29 August 2014, Debrecen, Hungary
Expected negative P balance in soils in developed countries
Trends in the use of P
Ryan et al. 2012
A Delgado13th ESA Congress25-29 August 2014, Debrecen, Hungary
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)
A Delgado13th ESA Congress25-29 August 2014, Debrecen, Hungary
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
A Delgado13th ESA Congress25-29 August 2014, Debrecen, Hungary
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 Delgado13th ESA Congress25-29 August 2014, Debrecen, Hungary
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 Delgado13th ESA Congress25-29 August 2014, Debrecen, Hungary
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
A Delgado13th ESA Congress25-29 August 2014, Debrecen, Hungary
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 Delgado13th ESA Congress25-29 August 2014, Debrecen, Hungary
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 Delgado13th ESA Congress25-29 August 2014, Debrecen, Hungary
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 Delgado13th ESA Congress25-29 August 2014, Debrecen, Hungary
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
A Delgado13th ESA Congress25-29 August 2014, Debrecen, Hungary
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
A Delgado13th ESA Congress25-29 August 2014, Debrecen, Hungary
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 Delgado13th ESA Congress25-29 August 2014, Debrecen, Hungary
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
A Delgado13th ESA Congress25-29 August 2014, Debrecen, Hungary
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
A Delgado13th ESA Congress25-29 August 2014, Debrecen, Hungary
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 Delgado13th ESA Congress25-29 August 2014, Debrecen, Hungary
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)
A Delgado13th ESA Congress25-29 August 2014, Debrecen, Hungary
Cordell et al. 2009
Recycling at smaller scales?
A Delgado13th ESA Congress25-29 August 2014, Debrecen, Hungary
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
A Delgado13th ESA Congress25-29 August 2014, Debrecen, Hungary
13th ESA Congress25-29 August 2014, Debrecen, Hungary A Delgado
PHOSPHORUS FERTILIZATION: A GLOBAL CONSTRAINT IN THE FUTURE?
Antonio DelgadoUniversity of Seville