Long-term no-tillage practices can impact legacy phosphorus in soils. No-tillage increases the total phosphorus stock in top soils over time compared to conventional tillage. Both inorganic and organic phosphorus pools are larger under long-term no-tillage as it favors the release of phosphorus from these pools. Case studies show higher levels of plant-available and labile phosphorus under no-tillage. While no-tillage can help manage legacy phosphorus for crop uptake, more research is needed to understand how tillage impacts different forms of phosphorus. Pairing no-tillage with residue retention and organic amendments can effectively manage legacy phosphorus stocks.

1. Impact of Long-term No-tillage Practices on
Legacy Phosphorus in Soils
Agricultural Chemistry and Soil Science
Faculty of Agriculture
Bidhan Chandra Krishi Viswavidyalaya
Speaker: Jaison M
Chairman: Prof. Biswapati Mandal
Seminar II Course No. ACSS-849 Date: 13/02/2020
Seminar Committee: Prof. P.K. Mani
Prof. P.K. Bandyopadhyay
Prof. S. K. Patra

2. Legacy phosphorus
• Phosphorus which got accumulated in soil as a result of past
management practice is called as Legacy Phosphorus.
• This accumulated P can leak for decades to downstream
lakes and coastal areas where it contributes to environmental
problems. (Kleinman et al., 2011).

3. Background: Global phosphorus cycle (Past)
i. Tectonic uplift and exposure
of phosphorus-bearing rocks to
the forces of weathering
ii. Physical erosion and chemical
weathering of rocks producing
most of bio-available P in
terrestrial regions
iii. Riverine transport of
phosphorus to lakes and the
ocean
iv. Sedimentation of phosphorus
associated with organic and
mineral matter and burial in
sediments Filippelli, 2008

4. Phosphorus inputs have increased at
least fourfold through the use of
fertilizers
(Chen and Graedel, 2016)
Over the same period, P
Sedimentation to coastal oceans have
increased at least threefold
(McCrackin et al., 2018)
Change in P Inflow-Outflow

5. Pédro, 2012
Altered global P cycle post-industrial revolution
The P cycle in biosphere is misbalanced because P tends to accumulate at a rate of 1 to
1.55×107 t P per year in soils (Pédro 2012)
Phosphoric rocks:
4 x 109 Tg
Soil :
2 x 105Tg
(2000 years)
Fertilizer:
17 Tg yr-1
Bioavailable: 3000
Tg yr -1
(47 years)
Rivers and lakes
Algae and fish: 140
Tg (0.13 yr-1)
Ocean surface: 2700
Tg (2.6 yr-1)
Deep ocean: 8.7 x
104 Tg
Ocean sediments: 4 x
109 Tg
(2 million years)
Increased rate: 10-15.5
Tg yr -1
Potentially extractant:
10-15.5 Tg yr -1
Increased rate
of addition of
P in soil
Sedimentation
of P got
increased
Very slow
process

6. Time lags causing accumulation…
Sharpley et al., 2014
Decline in crop
uptake of soil P
Higher P fixation by
soils
Slow release of
fixed P from soils
Soil
processes

7. Planetary boundaries
Rockstorm et al., 2009

8. P Imbalance all over the world
Filippelli, 2008

9. Finite P reserves…
Cordell et al., 2009
Phosphate rocks are also very
limited concentrated in few places
all over the world.
Phosphorus is a non-renewable
resource, like oil. Studies claim at
current rates of extraction, global
commercial phos- phate reserves will
be depleted in 50–100 years.

10. Strategies for
utilization of
legacy P
Fertilizer
management
Breeding
approaches
Legacy P
activators
Crop
management
practices
Blackburn et al., 2017
Options for legacy Phosphorus management

11. Fate of P in Conventional Tillage
Fixation
Mineralization
Immobilization
Soil
solution
PCa, Fe and Al
minerals
Labile and
moderately labile
Pi
Microbial
biomass P
Labile Po
Inositol and
Humic P
Assmilation
Death
Adsorption/
precipitation
Desorption/
Solubilization
Enzymatic
hydrolysis
Enzymatic
hydrolysis
Erosion
Runoff losses
Microbial
activity
affected
Eutrophication
Fertilizer
application
Intensive Tillage
Puddling
Higher
fixation
of P
Li et al., 2017

12. Mineralization
Immobilization
Soil
solution
PCa, Fe and Al
minerals
Labile and
moderately labile
Pi
Microbial
biomass P
Labile Po
Inositol and
Humic P
Assmilation
Death
Adsorption/
precipitation
Desorption/
Solubilization
Enzymatic
hydrolysis
Enzymatic
hydrolysis
Fertilizer
application
Root biomass
retained
Reduced or No-
tillage
Mineralization
Desorptionor
solubilization
Enzymatic
hydrolysis
Enzymatic
hydrolysis
Assimilation
less Run off
losses
Reduced
fixation in
less soluble
forms
Organic P
Utilization
Fate of P in Reduced/ No-tillage
Li et al., 2017

13. Case studies

14. Total P budget (kg P ha-1) in the topsoil for the
period 1979–2002 in loess soils of Australia
Bunemann et al., 2007
Treatments
Total P output
(kg ha-1)
Input output
budget
(kg ha-1)
Total P in top soil(kg ha-1
)
1973 2003 Change
WL-M-C 197b
+283bc 779n.s. 965n.s. 186n.s.
WL-B-C 256a
+224bc 791n.s. 970n.s. 180n.s.
WW-B-C 177b
+303b
780n.s.
999n.s.
219n.s.
WS-M-N 144c +336a 756n.s.
1054n.s. 297n.s.
WS-M-C 139c +341a 720n.s.
905n.s. 184n.s.
p (treat.) <0.001 <0.001 0.059 0.21 0.073
Total input with fertiliser 480 kg P/ha in all treatments.
W-Wheat, L-Lupin, S-Subterranean clover, B-Burning, M-Mulch, C- Conventional
tillage, N-No tillage,

15. Phosphorus balance after 23 years of different soil
management and winter crops of a Brazilian Oxisol
Teicher et al., 2012
Tillage Cropping
P
Applied
(kg ha-1)
Exported
(kg ha-1)
Available
(kg ha-1)
Recovered
(kg ha-1)
Recovered
(%)
NT O-M-S 660 260 197 457 69
NT V-M-S 660 252 141 393 60
NT W-M-S 660 278 123 402 61
CT W-M-S 660 232 84 316 48
NT-No tillage, CT- Conventional, O-Oats, M-Maize, S-Soyabean

16. Distribution of Inorganic P pools in arable top soils (0–20 cm) of four
Brazilian Oxisols under different tillage management
Rodrigues et al., 2016

17. Effect of soil tillage on different Inorganic P pools in
top soils of Spanish Vertisols
0
50
100
150
200
250
300
350
400
450
labile P moderately labile P Non labile P Residual P
Pmg/kg
Inorganic P
No-till Conventional tillage
Saavedra et al., 2007

18. Distribution of Organic P pools in arable top soils (0–20 cm) of four
Brazilian Oxisols under different tillage management
Rodrigues et al., 2016

19. Effect of soil tillage on different Organic P Pools in
top soils of Spanish Vertisols
0
20
40
60
80
100
120
labile P moderately labile P Non labile P Residual P
Pmg/kg
Organic P
no till Conventional tillage
Saavedra et al., 2007

20. Soil phosphatase potential activities in Oxisols under
different tillage and residue management
Margonet et al., 2017T+: Conventional tillage, T- : No tillage

21. Maximum phosphorus adsorption capacity (Pmax) in the
three soils under Different tillage system
Lowercase letters compare soil management systems and Uppercase letters soil layers.
Fink et al., 2016a

22. Adsorption of phosphorus (Pads), desorption with water (PW)
and desorption with Mehlich-I solution (PM) after different
times in Oxisols of Brazil
Fink et al., 2016b

23. Adsorption of phosphorus (Pads), desorption with water (PW) and
desorption with Mehlich-I solution (PM) after different times in
Ultisols of Brazil
Fink et al., 2016b

24. Phosphorus desorbed by resins as a function of time
for the different tillage treatments in Vertisols of Spain
Saavedra et al., 2007

25. Teicher et al., 2018
Relationship among soil P forms in organic and inorganic
pools in soil under 23-yrs of conventional tillage.
Bubbles indicate the P-pool size. Black arrows indicate significant paths.

26. Relationship among soil P forms in organic and inorganic
pools in soil under 23-yrs of No tillage.
Teicher et al., 2018Bubbles indicate the P-pool size. Black arrows indicate significant paths.

27. Conclusion
o Management of legacy Phosphorus towards crop uptake is
crucial in both agricultural and environment point of view.
o Total P stock in top soils is increased by Long-term no-tillage
practices.
o Inorganic P and organic P pools are improved by long-term
practice of no tillage/ reduced tillage.
o Long term no-tillage is found to favour release of P from both
inorganic and organic pools of P in soils.
o More research directed towards the process level changes that
happens on different forms of P affected by tillage is needed.
o Coupling no-tillage with residue retention, organics application,
optimum rate of fertilization will be effective way of
management of P- legacy.

28. Thank you