Pr

1
Phosphorus in manures and other organic products
What limits proper recycling of this resource in
agriculture?
Sylvain PELLERIN, Christian MOREL, Thomas NESME,
Bruno RINGEVAL
NOM DE LAUTEUR
03 / 12 / 2013
2

• Outline
• Background
• Four barriers / issues for optimal recycling of
  P from manures
• Geographical segregation between livestock and
  crop production systems
• Inadequate N/P ratio
• Mismatch with temporal crop requirements
• Uncertainties in P fertilizing value assessment
• Conclusion

Phosphorus in manures and other organic products
02 Sept 2014
3

• P in organic products
• 4 - 40 mg P per kg dry matter
• Swine slurry gt Urban sewage sludge gt Beef/Cattle
  manure gt Urban composts
• High variability (due to variability of animal
  diets, manure processes,)
• Inorganic P ? 55-95 of total P

Morel et al., unpublished
Phosphorus in manures and other organic products
02 Sept 2014
4
Organic fertilisers are as effective as mineral
fertilisers for mid-term soil P fertility
build-up
? Poultry litter
? Triple superphosphate (TSP)
? Poultry litter TSP
P balance (kg P ha-1)
Shepherd and Withers, 1999
Phosphorus in manures and other organic products
02 Sept 2014
5
At the global scale, the amount of P in manures
represents 17 Tg P.y-1 (more than P in mineral
fertilizers) But P budget calculations suggest a
non-optimal use of this resource ? Assuming an
 optimal  manure P recycling, the need for
additional mineral P would be much lower than
actually observed (2 instead of 14 Tg P y-1)
P, Tg.y-1 (year 2000)
P manure 17
P fertilizers 14
Total P input 31
P withdrawal 19
Bouwman et al., PNAS, 2011
Phosphorus in manures and other organic products
02 Sept 2014
6
Only partial substitution of mineral P by P from
organic products is also observed at local
scale Ex of France 76 agricultural districts,
approx. 5000 km2
Nesme et al., 2014
Phosphorus in manures and other organic products
02 Sept 2014
7
What limits proper recycling of this P resource?
Phosphorus in manures and other organic products
02 Sept 2014
8

• Farm specialisation and increasing geographical
  segregation between livestock and crop production
  systems
• hamper the use of manure as a P fertilizer source
  in specialised arable farming regions
• are responsible for excess P in animal farming
  regions

Livestock density (LU ha-1) P manure (kg P ha-1)
P mineral fertilisers (kg P ha-1)
Source Eurostat
Phosphorus in manures and other organic products
02 Sept 2014
9
P budgets for two contrasted French agricultural
regions
Brittany
Centre
Phosphorus in manures and other organic products
02 Sept 2014
10
Intensive animal farming region (Brittany)
?The soil P budget is highly positive ( 18.9 kg
P ha-1 yr-1) ?High P inflows due to feed imports
(28.9 kg P ha-1 yr-1) and fertiliser use (7.9 kg
P ha-1 yr-1) ?Even without P fertiliser use, the
soil P budget would remain positive
Senthilkumar et al., 2012
Phosphorus in manures and other organic products
02 Sept 2014
11
Intensive arable farming region (Centre)
? The soil P budget is close to the equilibrium
(1.1 kg P ha-1 yr-1) ? However, crop exports
are supported by massive mineral P fertiliser
imports (12.9 kg P ha-1 yr-1)
Senthilkumar et al., 2012
Phosphorus in manures and other organic products
02 Sept 2014
12
2. Organic fertilising materials have low N/P
ratio. If used for N targeted fertilisation they
lead to soil P excess ? this P accumulates in
soils ? and is no longer available as a
substitute for mineral P elsewhere
N/P ratio
Leaf N/P ratio (TRY global database, Kattge et
al., 2011)
N/P ratio of harvested organs (15 arable and
forage crops)
Crops (15)
Morel et al., unpublished
.03
Phosphorus in manures and other organic products
02 Sept 2014
13
Example of a N-P budget for wheat fertilised with
cattle manure
Target yield Mg dry matter ha-1 N content in grain mg g-1 dry matter P content in grain mg g-1 dry matter N exports kg N ha-1 P exports kg P ha-1 Amount of cattle manure required to compensate N exports kg DM ha-1 Amount of P supplied kg P ha-1 N budget kg N ha-1 P budget kg P ha-1
8 20 3 160 24 6400 44.8 0 20.8
.03
Phosphorus in manures and other organic products
02 Sept 2014
14
3. Questions remain about the ability of P from
organic fertilizers to match crop requirements in
time Ex of the early  critical stage  on
maize Mineral P  starter fertilisers  are
often used by farmers to supply high P
concentrations close to the roots during this
critical stage This questions the ability of
organic products to act as an effective
substitute to soluble mineral fertilisers in this
context Moreover, scheduling applications of
organic fertilisers is often constrained by
practical aspects (trafficability, etc)
P demand (mg P km-1 d-1)
Mollier, 2013
.03
Phosphorus in manures and other organic products
02 Sept 2014
15
POF
PMF
0 P
4. Methodological issues and uncertainties in P
fertilizing value assessment
Classical approach Standardized plant P tests
This approach may be misleading because it
assumes that the amount of P taken up by plants
originating from the soil is not modified by
experimental treatments (Puptakecontrol) ?
Standardized plant test using labelling
techniques (32P or 33P) are more reliable, but
require dedicated laboratory facilities.
.03
Phosphorus in manures and other organic products
02 Sept 2014
16
Fertilising value ( soluble mineral fertiliser) Fertilising value ( soluble mineral fertiliser)
Labelling No labelling
Farmyard manure 68 207
Poultry manure 43 407
Soluble mineral fertiliser 100 100
Mohanty et al., 2006
.03
Phosphorus in manures and other organic products
02 Sept 2014
17
Reliable studies show that the short term P
fertilising value of animal manures is generally
high
Relative efficiency ( of soluble mineral fertiliser)
Organic sources Range
Pig manure 84-102
Beef manure 68-111
Poultry manure 43-88
But it remains that the short-term dynamics of P
after manure application may be affected by many
factors (e.g. P immobilisation by microbial
biomass if high C/P ratio)
? Standardized plant tests are useful tools to
rank organic products in standardized
conditions ? We need a better understanding of
the short term fate of P after manure application
in field conditions
.03
Phosphorus in manures and other organic products
02 Sept 2014
18
Summary and Conclusion

• Organic fertilisers are as effective as mineral
  fertilisers for mid-term soil P fertility
  build-up.
• Reliable results suggest that short term P
  availability in manures is generally high,
  although variable
• Optimal substitution of mineral P by P from
  organic products is limited by
• the increasing geographical segregation of animal
  and crop farming regions,
• inadequate N/P ratio,
• Questions about the ability of P from organic
  fertilizers to match crop requirements in time
• Uncertainties in P fertilizing value assessment
• Practical constraints (storage, handling,
  trafficability) may also act as barrier

.03
Phosphorus in manures and other organic products
02 Sept 2014
19
Summary and Conclusion

• Innovations are needed
• To reconnect livestock and crop production
• Regulation on maximum livestock densities?
• Exchange markets of manures
• Technologies to reduce volumes and transportation
  expenses (granular, pellets,)
• Recovery options (struvite precipitation,)
• to get a NP ratio better adapted to plant
  requirements
• Reduce P content in manure by re-aligning P diets
  on animal requirements,
• Increase N content by reducing N gaseous losses
• A research effort is still needed to better
  understand and predict short term P release and
  availability for plants after application

.03
Phosphorus in manures and other organic products
02 Sept 2014
20
Thank you for your attention
.03
Phosphorus in manures and other organic products
02 Sept 2014
21
(No Transcript)
22
Today, the lack of robust references about short
term P fertilising value of organic products may
partly explain why farmers do not fully take into
account manure application as mineral dose
diminishing factors
.03
Phosphorus in manures and other organic products
02 Sept 2014
23
More reliable approaches are based on labelling
techniques
(4) Calculation of the fraction of the P taken up
by plants which derives from the fertilizer
(Pdff, in )
(3) Determination of the 31P and 32P quantities
in aerial parts
Control (0P)

• (2) 50 mg P kg -1 soil applied as
• Organic fertiliser (OF)
• or Triplesuperphosphate (MF)

(1) Isotopic labelling of plant-available soil P
with 32P-PO4 or 33PO4
.03
Phosphorus in manures and other organic products
02 Sept 2014