Food production requires application of fertilizers in the form of N, P and K on agricultural fields to sustain crop yield. Last year 50 million metric ton of phosphatic fertilizers were used worldwide by this sector and their demand is increasing on average @ 1.6% from last three decades. Current intensive cropping systems remove significant chunk of P from soil, so now almost 43% of the world’s soils are P deficient. There is a dire need of continuous application of P fertilizers to the soil to cope up this deficiency. Rock-phosphate is a finite resource and current reserves are 71 billion metric ton. Compared to 1.6% annual increment in their consumption, it is possible that these resources will be depleted in 150-200 years.

1. Smart Phosphorus Fertilizers for Sustainable
Agriculture
Ahmad Kamal
2015-ag-6508
AGR-720
PhD. Agronomy, 2nd Semester
Department of Agronomy
1

2. Outline
• Introduction
• Why need Smart Fertilizers for Sustainable Agriculture?
• Slow or Controlled Released P Fertilizers
• Phosphorus Bioformulations
• Biochar Coated Fertilizer
• Nanofertilizer
• Constraints to achieve Smart Fertilization
• Conclusion
• References
2

3. Introduction
• Food production requires application of fertilizers in the form of N, P and K on agricultural fields
to sustain crop yield
• Last year 50 million metric ton of phosphatic fertilizers were used worldwide by this sector and
their demand is increasing on average @ 1.6% from last three decades
• Current intensive cropping systems remove significant chunk of P from soil, so now almost 43% of
the world’s soils are P deficient
• There is a dire need of continuous application of P fertilizers to the soil to cope up this deficiency
• Rock-phosphate is a finite resource and current reserves are 71 billion metric ton. Compared to
1.6% annual increment in their consumption, it is possible that these resources will be depleted in
150-200 years
(Cordell et al., 2009)
3

4. Introduction
• Efficiency of mineral P fertilizers is 20-25% all over the world, the available P to the plant is as
low as 1 mg kg-1
• This triggers the excessive P fertilization which lead to increased fixation, leaching and
environmental hazards such as eutrophication of lakes
• To check P fixation in the soil and environmental pollution caused by excessive usage of P
fertilizers, there is a need to develop fertilizers that cater above challenges
• Smart phosphate fertilizers could offer practical solution in this regard
(Cordell et al., 2009)
4

5. Introduction
Factors affecting P
fixation on soil
Soil
minerals
Soil pH
Soil OM Temperature
(Foster, 2013)
Cation and
anion effect
5

6. Introduction
• According to Foster, “Smart fertilizer is any single or composed nanomaterial, coating or
bioformulation containing one or more nutrients that through physical, chemical and biological
processes can adapt the timing of nutrient release to plant nutrient demand, thus enhancing the
agronomic yields and reducing the environmental impact at sustainable costs compared to
conventional fertilizers”
(Foster, 2013)
6

7. Introduction
Why we need Smart Fertilizers?
Eradication
of hunger
and poverty
Preservation
of
environment
Cure for
cultivation
within
urbanization
(Foster, 2013)
7

8. Slow or Controlled Released P Fertilizers
• Fertilizers that contains nutrients in a form that either delays its availability for nutrient uptake and
use after application or is available to the plant for longer period than the reference fertilizer
Criteria for CRP
at 25 °C
< 15% of applied nutrient
released in 24 hours
< 75% of applied nutrient
released in 28 days
75% of applied nutrient is
released at stated release
date
(Naz and Sulaiman, 2016)
8

9. Slow or Controlled Released P Fertilizers
• Two types of coating materials are used for coating of CRP fertilizers
• First one is the synthetic polymers such as polysulfone, polyacrylonitrile, polyvinyl chloride,
polyurethane and polystyrene
• Synthetic polymers are mostly used to encapsulate water soluble fertilizer granules
• The second type of coating material is biodegradable polymer such as biopols, polylactic acids,
alginates, starches and agar
• Though biodegradable polymers are cheap and environment friendly, but they still need to be
blended with synthetic polymers to increase their performance
(Du et al., 2006)
9

10. Slow or Controlled Released P Fertilizers
Core
Chitosan-
clay inner
coating
Outer coating
of paraffin wax
Fig: Structure of double coated DAP granule (Assimi et al., 2020)
10

11. Slow or Controlled Released P Fertilizers
• Dissolution from CRP fertilizers depends upon coating thickness, solute permeability, granule
properties (density and solubility), humidity and temperature
• Reduce the ineffectiveness of conventional P fertilizers by lowering effective surface area available
for contact with aluminum, calcium, iron and other cations which immobilize P
• Prevent P fixation in soil via sorption, complexation and precipitation. They also check rapid
dissolution and loss of surface runoff and subsurface flow
• CRP fertilizers, releases P according to the demand of the plant, which not only improves PUE and
crop yield but also reduces the environmental risk posed by the excessive use of fertilizers.
Ensuring food security by sustainable utilization of land and fertilizer resources
(Roberts and Johnston, 2015)
11

12. Release Mechanism of Slow or Controlled
Released P Fertilizers
12
 H2O entry into
granule
 Nutrient dissolution
 Coating material
 Steep conc. gradient is
developed inside coated
product and soil P
solution
Interior granule is dissolved and
P conc. gradient becomes in
equilibrium with soil solution and
release rate ceases
Withering Phase
Release Phase
Lag Phase
(Weeks et al., 2019)

13. Phosphorus Bioformulations
• These are the substances that contain active phosphorus solubilizing microorganisms
• Different types of phytate-mineralizing, phosphorus solubalizing bacteria (Pseudomonas spp. and
Bacillus spp.) and fungi (Pencillium spp. and Aspergillus spp.) are used as carrier materials or
bioformulations
• Different coating materials like alginate gels, vermiculites, polysaccharides, biochar, charcoal, peat
and humics are used for immobilization and preservation of microbes
• Microorganisms are encapsulated in these materials for storage, to protect them from
environmental hazards (temperature and pH), and rendering a gradual slow release effect
(Calabi et al., 2018)
13

14. Phosphorus Bioformulations
Temperature
pH
H2O
PSM
Ca-aliginate
coating
Rupture of
coating and
release of PSM
(Calabi et al., 2018)
Fig: Schematic representation of model
encapsulated microbial formulation 14

15. Phosphorus Bioformulations
• Bio Gold is a liquid formulation that contains
native isolates of Pseudomonas fluorescens
• It may be applied by spraying around the root
zone, by drip irrigation and as a seed inoculant
• It also produces secondary metabolites that are
effective against rot and wilt diseases of
nursey seedlings
(Mehnaz, 2016)
15

16. • AgriVAM is a bioformulation based on spores
and fragments of VAM (Glomus spp.) with
vermiculite as carrier
• Applied to soil, seed and nursery bed at
planting stage
• It increases water absorption, phosphorus
solubilization, micronutrient availability,
drought tolerance and resistance to soil borne
fungal pathogen
(Mehnaz, 2016)
Phosphorus Bioformulations
16

17. Phosphorus Bioformulations
Mechanism of P Solubilization
(Kalaya, 2019)
17

18. Biochar Coated Fertilizer
• Biochar is a product obtained through pyrolysis of agricultural or other lignocellulosic biomass at
temperature ranging from 350 °C to 700 °C
• When biochar material is employed as coating around fertilizer granules to render them slow
release characteristics, the resulting product is called biochar coated fertilizer (BCF)
• Feedstock (wood, rice and wheat residues, bagasse and manures)
• Natural binders (clay, starch, lignin and bentonite)
• Pyrolysis temperature
(Zhao et al. 2016)
18

19. Biochar Coated Fertilizer Granules
(Rombel et al., 2021)
Fig: Biochar coated TSP and
Urea granules
19

20. Biochar Coated Fertilizer
P bound by chemical
(covalent) bonds is
released
P release mechanism of BCF
Release of labile
form of P from
granule and
dispersion on biochar
coated surface
P bound through
intermolecular forces of
attraction and H-bonds
with BC is released
(Sim et al., 2021)
20

21. Nanofertilizer
• Nanofertilizers are powder or liquid formulations that involve the synthesis, design, and use of
materials at the nanoscale level
• Synthesized by top down (Physical), bottom up approaches or green synthesis
• Have small particle size and high surface to volume ratio that renders high nutrient bioavailability
and uptake
• Natural materials such as nano clays, zeolites, laponite, saponite and vermiculite are used as
coating
• Their crystalline layers are filled with macro and micronutrients so that nutrients slowly release on
requirement
(Panpatte et al., 2016)
21

22. Nanofertilizer
(Saleem et al., 2021)
Fig: KFeO2 NPs coating on DAP to promote slow release of N and P
Slow release
of HPO4
-2
and H2PO4
-
22

23. Constraints to achieve Smart Phosphorus
Fertilizers
Bottlenecks
for Smart P
Fertilizers
Financial
Resources
Shelf Life
Technical
Knowledge
Small
Holdings
23

24. Conclusion
• Declining phosphate rock resources and their burgeoning prices on horizon is major threat to
global food security
• Smart phosphorus fertilizers have showed the capability to improve crop yields, reduce soil
pollution and lower fixation losses compared with conventional fertilizers
24

25. References
• Assimi, T., Lakbita, O., El Meziane, A., Khouloud, M., Dahchour, A., Beniazza, R., ... and M.
Lahcini. 2020. Sustainable coating material based on chitosan-clay composite and paraffin wax for
slow-release DAP fertilizer. Int. J. Biol. Macromol. 161: 492-502.
• Calabi-Floody, M., Medina, J., Rumpel, C., Condron, L. M., Hernandez, M., Dumont, M., and M.
de la Luz Mora. 2018. Smart fertilizers as a strategy for sustainable agriculture. Adv. Agron. 147:
119-157.
• Cordell, D., Drangert, J. O., and S. White. 2009. The story of phosphorus: global food security and
food for thought. Glob Environ Change. 19(2): 292-305.
• Du, C. W., Zhou, J. M., and A. Shaviv. 2006. Release characteristics of nutrients from polymer-
coated compound controlled release fertilizers. J Polym Environ. 14(3): 223-230.
• Foster, A. 2013. Development of Biocompatible Aptamer Films as Smart Materials for Novel
Fertilizer Systems (Doctoral dissertation, Carleton University).
• Kalayu, G. 2019. Phosphate solubilizing microorganisms: promising approach as biofertilizers. Int.
J. Agron. pp: 1-7.
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26. References
• Mehnaz, S. 2016. An overview of globally available bioformulations. Bioformulations: For
sustainable agriculture. Springer, New Delhi. pp: 267-281.
• Naz, M. Y., and S.A. Sulaiman. 2016. Slow release coating remedy for nitrogen loss from
conventional urea: a review. J. Control. Release. 225: 109-120.
• Panpatte, D. G., Jhala, Y. K., Shelat, H. N., and R. V. Vyas. 2016. Nanoparticles: the next
generation technology for sustainable agriculture. In Microbial inoculants in sustainable
agricultural productivity. Springer, New Delhi. pp: 289-300.
• Roberts, T. L., and A.E. Johnston. 2015. Phosphorus use efficiency and management in agriculture.
Resour Conserv Recycl . 105: 275-281.
• Rombel, A., Krasucka, P., and P. Oleszczuk. 2021. Sustainable biochar-based soil fertilizers and
amendments as a new trend in biochar research. Sci. Total Environ. 816: 151588.
• Saleem, I., Maqsood, M. A., ur Rehman, M. Z., Aziz, T., Bhatti, I. A., and S. Ali. 2021. Potassium
ferrite nanoparticles on DAP to formulate slow release fertilizer with auxiliary nutrients.
Ecotoxicol. Environ. Saf. 215: 112148.
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27. References
• Sim, D. H. H., Tan, I. A. W., Lim, L. L. P., and B.H. Hameed. 2021. Encapsulated biochar-based
sustained release fertilizer for precision agriculture: A review. J. Clean. Prod. 303: 127018.
• Weeks Jr, J. J., and G. M. Hettiarachchi. 2019. A review of the latest in phosphorus fertilizer
technology: Possibilities and pragmatism. J. Environ. Qual. 48(5): 1300-1313.
• Zhao, L., Cao, X., Zheng, W., Scott, J. W., Sharma, B. K., X. Chen. 2016. Copyrolysis of biomass
with phosphate fertilizers to improve biochar carbon retention, slow nutrient release, and stabilize
heavy metals in soil. ACS Sustain. Chem. Eng. 4(3): 1630-1636.
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