Biostimulant and Fish Liver Cod Oil Used on Trees

A recent TV show featured lesser known jobs in Singapore, called Sherlock at Work and it was hosted by Pornsak Prajakwit. In episode 5, the topic was on arborists, and Pornsak followed an arborist around for a "day in the life of an arborist". The show was uploaded to Toggle Video on 23 Nov 2016.

In one segment, after showing Pornsak on the use of resistograph and reasoned that the tree she was examining seemed to be in good health, she proceeded to ask Pornsak to apply mulch at the tree base. Following that, biostimulants and fish liver cod oil was applied into the ground near the tree using a hollow probe.

Liquid tank from which the biostimulant and fish liver cod oil was pumped from. (Screengrab credit: Mediacorp)

Ta-da biostimulant. (Screengrab credit: Mediacorp)

The host of the show applying the liquid mixture into the ground and the arborist supervised. Note the girth of the tree being treated and distance from the tree that probe was inserted. (Screengrab credit: Mediacorp)

Liquid emerging from the ground, or did the liquid not go into the ground? (Screengrab credit: Mediacorp)

Root spread of trees

The rule of thumb in arboriculture states the following regarding root spread:
1. Tree root systems extend out several times of the tree's diameter (depending on the age of tree).
2. More than 60 percent of the absorbing root system is beyond the dripline.
3. Most roots are in the top foot (30.5 cm) of soil.

The hollow probe should be inserted further away from the tree, given the advanced age of the tree, as most of the absorbing roots that takes in water and nutrients are located at the edge of the root system (beyond the dripline). In addition, since a fancy concoction was being used, it should be applied deeper than the surface of the ground, in order to avoid being absorbed by the grasses, being evaporated, and flowing away.

What are biostimulants?

Biostimulants are a group of compounds that promote favourable plant responses and are non-nutritional. Common commercial biostimulants contain many, if not all of the following ingredients:
- Plant hormones/Plant growth regulators
- Humic compounds
- Sea kelp extract and/or organic matter

Some of the claims reported by biostimulant manufacturers include:
- Stimulate plant responses and work in all weather conditions
- Increase natural plant toxins, repelling pests
- Increase microbial root protection from soil pathogens
- Improve root development
- Improve drought tolerance
- Increases nutrient uptake
- Stimulate plant's immune system
- Produce deeper roots
- Improve stress tolerance
- Accelerate establishment
- Increases Cation Exchange Capacity
- Enhances fertilisation and reduces leaching
- Detoxify chemical residues and heavy metals
- Increase stomata opening and plant transpiration

University studies on biostimulants do not fully agree with the claims usually made by manufacturers especially with regards to reducing fertiliser and pesticide use. However, there are positive reports that biostimulants show potential uses in turf under stress conditions and promote favourable nutrient mobilisation, although the responses to biostimulant may vary depending upon the biostimulant formulation and among species.

Harris et al. (1997) concluded that biostimulants appeared to be not useful if good transplanting methods were practiced with burlapped trees. This is consistent with the principle that under normal growing conditions, plants are self-sufficient and do not respond to an exogenous supply of hormones.

Another group of researchers (Zhang and Schmidtt, 1999) found that biostimulants does not stimulate much plant growth. One could conclude that a balanced fertiliser and compost application produces biostimulant-like responses, i.e., shoot growth, increase nutrient uptake, and photosynthate ("food" made by the plant with photosynthesis) translocation.

References

Harris, J. R., Fanelli, J., and Knight P. 1997. SNA Research Conference. 42: 369-372

Zhang, X. and Schmidt, R. E. 1999. Biostimulating turf-grasses. Ground Maintenance. 34(11): 14-32

 Show credits (Screengrab credit: Mediacorp)