Kelp, Humic acid and other bio-stimulants need to be used properly

Materials like kelp, humic acid and fish emulsion are not fertilizer. Each stimulates the activity of a different group of microbes in the soil.

For some time now, the number of products described as “Soil Conditioners” or “Soil Improvers” has been growing. Makers of things like Kelp Extracts, Humic Acid, Fish Emulsion make numerous claims about improving the soil and reducing fertilizer applications, but it has been unclear whether or not there is any real basis to these claims.

Some people have had amazing results with one thing or another, but for many the results have been slight or imperceptible and the reason for this variable effectiveness has remained elusive.

Recent research by SWEP laboratories, however, has begun to shed light on this issue. Since the release of their Complete Soil Balance Analysis, they have been able to look more closely at what happens when various materials are applied to soil. While still in its early stages, results from this research are pointing to real effects that should give more predicable results.

Kelp extracts

Kelp is amongst the oldest organic products on the market and, like most others, began by being marketed as a fertilizer alternative. Although containing a wide range of elements and possibly beneficial as trace element supplements, it quickly became apparent that there was too little of any nutrient (especially once diluted for application) for these materials to really be thought of as fertilizers. Some manufacturers have tried to compensate for this by fortifying their products with dissolved fertilizer, but this has seldom been entirely effective.

Another strategy has been to increase the concentration of the solutions applied. This did produce results, but contrary to most expectations, it often produces a negative response. In other words, it stopped plants growing!

Subsequent research confirmed a high concentration of plant hormones in kelp products. This explained the ‘overdose’ response and led to a change to foliar application in preference to soil treatment.

SWEP research has shown that these hormones also have strong effects on soil microbes. In particular, it has been shown that kelp extracts stimulate activity in Photosynthetic bacteria and especially Actino-bacteria.

The research also showed a critical concentration that appears to be related to the concentration of the product. For most established brands, this appears to be around 5 litres per hectare, with the response falling off rapidly both above and below this level.

Fish emulsions

These materials also have a long history, but with a number of different manufacturing methods. Again, they have been treated as fertilizer in spite of the low concentrations of most nutrients in the diluted solution applied and ‘fortified’ products have also been developed to compensate for this. However, they differ from Kelp extracts in being able to be used at higher concentrations and in usually having reasonable amounts of Nitrogen. The result is that they are more likely to ‘green’ things up and a fertilizer-like response.

This background made results from SWEP research something of a surprise. The most significant result came from the specialized Fungi termed ‘Cellulose utilizers’. This group was expected to be intolerant of added Nitrogen and so the result was the reverse of what was expected. Other Fungi also showed significant increases in activity.

However, unlike kelp there appeared to be two critical concentrations at which fish emulsions could be applied. Fungi and Cellulose utilizers responded at the lowest application rate – 2 litres per hectare, while at 10 litres per hectare the response was more like that of Kelp – Actino-bacteria and Photosynthetic bacteria.

Interestingly, the activity of Lactic acid bacteria appeared to be suppressed by Fish Emulsion, with this suppression increasing as the application rate decreased!

These responses would appear to make kelp and fish emulsion the most generally useful of all the bio-stimulant materials.

Humic acid

These materials are usually produced by liquefaction of Leonardite, although solid and soluble products have also appeared recently. These materials have never been regarded as fertilizers, but rather as “Soil conditioners”, due to their effects on soil structure. However, many criticisms about the use of Humates have pointed to the small amount of Carbon actually applied, compared with the increases in Soil Organic Carbon that manufacturers claim. Others dismiss these criticisms, saying that humates act as catalysts for biological processes which lead to accumulation of organic matter in the soil.

Research by SWEP may actually support this latter contention, as it showed humates produce a similar change in microbial profile to Kelp extracts, but with a strong suppression of Lactic acid bacteria and stimulation of Cellulose utilizers. In a sense, these materials appear to work as if they were some kind of ‘hybrid’ between kelp extracts and fish emulsions, but generally at higher application rates. This finding also appears to support the general feeling among both manufacturers and users that combination products between two or more of these three materials can be more effective that each alone.

Due to the wide range of product formulations, there is probably no single effective application rate, but again the lower application rates appeared to be the more effective.

Molasses

The use of sugar and molasses to boost soil microbial activity has been talked about for some time and the theory has been that it is an energy source that can be utilized equally by all organisms. However, field applications have often failed to produce many convincing responses.

SWEP research with Molasses has shown significant effects on soil biology, but they are more complex than expected.

Again, the best results appeared to be at the lowest application rate (2 litres per hectare), with fermenters such as Lactic acid bacteria and Yeast predictably giving the strongest response, but with Fungi and Cellulose utilizers also responding at the lowest application rate.

Interestingly, Photosynthetic bacteria showed the opposite response with activity increasing as the application rate increased.

The results show that, if used carefully, Molasses could be a useful general 'tonic' for the soil, but probably far less useful than kelp, fish and humate.

Worm leachate

This material is relatively new to the market, with comparatively little research to support it. However, when applied to soil it does produce changes in the microbial profile, but th result depends on the application rate.

At low rates, worm 'juice' also stimulates cellulose fungi, but at high rates, it is the photosynthetic bacteria that respond.

It is clear that each material has its own effect on soil biology. Indicating that there are both appropriate and inappropriate uses and application rates.

Unfortunately, there is unlikely to be any simple “Rule-of-thumb” to apply for the use of any bio-active material. The only way to know what will be effective for any soil is to base decisions on the results of a suitable soil test.