Seed coating technologies agriculture.pdf

Seed Coating technologies

1. BiopolymericSystem for Seed
Coating and Encapsulation
Antonio Di Martino
[email protected]

2. Seed coating : Introduction
Seed coating is the practice of covering seeds with external materials to:
improve handling(storage and sowing)
protection (e.gfungicides, pesticides, microorganisms, predators)
germination enhancement
crop yield
Seed coating is used to modify the physical properties of seed –
weight and size
Seed-coating technologies have been developed on crop and
vegetable species for the most while a lesser extent, on seeds of
turf grass, pasture, and flowers
There is a pressing needfor new approaches to seed-based
restoration and seed-coating for the restoration efficacy of native
seeds, most of which are collected from wild sources and represents a
finite resource not to be wasted

3. Seed coating

4. Seed coating : Ingredients
Liquid with adhesive proprieties
used to provide structural
support and retention of active
ingredients
Natural and Synthetic polymers
Methylcellulose
Ethylcellulose
Chitosan
PVA
Polyvinilacetate
Gum arabic
A powdery, inert material
used to increase seed
shape and size
Bentonite
Calcium carbonate
Talc
Diatomaceous earth
Sand
Wood dust
Binders and fillers must be compatible with active
compounds, and not impact the ability of a seed to
germinate and grow
Differences between the public and
private research
Industry: coloursand protectants (fungicides,
pesticides, insecticides, nematicides, predator
deterrents, and herbicides)
Academy: inoculants, nutrients, and
phytoactivepromoters

5. Seed coating : Technologies
film coating(usually < 10% of seed weight)
encrusting(weight increased up to 100–500% -
depending on seed morphology)
pellet(change in shape-oval or spherical)

6. Encapsulation VS Coating
Encapsulation = concept of synthetic seeds
Synthetic seeds are artificially encapsulated plant propagation material. This material could
be somatic embryos, shoot buds, cell aggregates, or any other tissue that we can use as a
seed for propagation. Synthetic seed technology primarily involves encapsulating somatic
embryos in a protective coating

7. Hydrogels for encapsulation
Hydrogels are three-dimensional (3D) cross-linked polymer networks, which can
absorb and retain large amount of water

8. Hydrogels for encapsulation
Nature Communications volume 10, Article number: 493 (2019)

9. Industry VS Academia
Industry Academia
Species
Ingredients
Industry Academia
Outcomes
scientific and industrial research sectors
have had limited interaction and that the
development of coating technologies
has followed separate paths

10. The issue related to the sowing
Sometimes is difficult to reach the sowing
area –especially in case of remote area
(forest)

11. Aerial seeding (aerial reforestation)
The technique of spreading seeds from an airplane, helicopter or any flying transport
Introduces seeds directly within the field and it's often not economical thanks to
the problems of germination, pests and seed predation by rodents or other wild
animals
Aerial seeding features a low yield and need 25% to 50% more seeds than
drilled seeding to realize an equivalent results

12. Seed bombs
The use of seed bombs, rather than simple seeds, to perform aerial reforestation
seems to possess produced desirable results
Many studies review report the use of seed pellets in agriculture however,
little work has been targeted for wildland restoration
The interestin the developing seed bombs is increasing either in industrial
or academic
The reasons for using seed pellets fall into four rough categories:
improved distribution
protection from seed predation and other disturbances
enhanced germination
enhanced establishment

13. Seed bombs -Advantages
Allows more species to be distributed with more kinds of equipment
Suitable for
very small seeds
plumose seeds (e.g. milkweed),
seeds with hairs or awns (e.g. cotton
top)
Once seeds have been distributed, they remain safelyin place until conditions
are suitable to promote germination, emergence, and establishment
The main threats to seeds are insects (often ants), small mammals, and birds,
although fungi can be a substantial threat to seed persistence in some situations

14. Not only sowing
The seed cover has to be designed with the potential to enhance
germination and establishmentin a variety of ways
Mechanisms thought to improve conditions include:
increased water holding capacity
decreased loss from evaporation
lower temperature and more thermal stability
and lower light conditions
Once seeds have been distributed, they need to safely remain in place until
conditions are suitable to promote germination, emergence, and establishment
The main threats to seeds are insects (often ants), small mammals, and birds,
although fungi can be a substantial threat to seed persistence in some situations

15. Importance of materials
Seed bombs are typically made of
clay
soil
water
seed
Additional ingredients :
rock dust, coffee grounds, sand, fertilizer, activated carbon, and mycorrhizal
fungi, repellant for predators
Ingredients are intended to
aggregate seed for efficient and effective mechanical distribution
protectseeds between the time of distribution and arrival of germinating conditions
amelioratedry conditions, soil crusts, and nutrient deficiencies that act as barriers
to seedling establishment

16. Hydrogel seed bombs : materials
Binder(bentonite up to 10%)
Support germination
–increase water content
Polysaccharides
Soil
Seeds
Sodium Alginate
Ethylcellulose
Carboxymethylcellulose
Chitosan Starch (corn)
Crosslinkers
Citric acid
CaCl2 MgCl2

17. Preparation
Bentonite
Mixing
&
shaping
Mixing
24h
Polysaccharides
solution
Soil
Seeds
Drying step
(room temperature)

18. Hydrogel Seed Bombs
Alginate/Starch/Soil-200 seeds
458 g wet –200 seeds
28g dried
Reswelling25-40%
Wet
Dried
CMC/Ethylcellulose/Starch/Soil
55g wet
6g dried –48h
Reswelling10-40%
Alginate/CMC /Ethylcellulose/Soil
Reswelling10-30%
4g
9g
Alginate/Starch/Ethylcellulose
Reswelling90-100%

19. Hydrogel Seed Bombs
Alginate/ Starch/ Bentonite
Alginate/ CMC/Ethylcellulose/Bentonite
Various weight and shape
Reswelling3-20% (depend on bentonite content)
Higher bentonite content –less reswelling
Higher bentonite content –more hard
No brittle

20. Hydrogel Seeds Bombs
Laboratory scale preparation
Limited volume (1 L )
Limited size and weight
Max wet weight 500g cc (alginate-soil)
Max wet weight 240g cc (alginate-bentonite)
Preparation time : 72h ( to obtain the dried
formulation)

21. Ongoing work…….
Germination
Seeds: lettuce
basil
parsley