Technical - Soil Biology
Seaweed extracts act as biostimulants on the microbes in the soil because of the carbon and carbohydrate content and diversity of nutrients that act as a microbial food source. Generally, potassium hydroxide extracted seaweed, which has a higher organic content than cold pressed solutions, is best for soil microbe growth and was shown to be a better biostimulant for bacterial and fungal growth than fish hydrolysate or complex sugars see photo 3. So, while seaweed itself does not make all the improvements attributed to it, the increase in beneficial soil biology does.
Seaweed extracts act as a biostimulant
Cold pressed seaweeds with a smaller molecular structure are more readily absorbed by the plant and work well on the plant, mainly due to the presence of plant hormones: auxins, cytokinins, gibberellins. Auxins are responsible for elongational growth of plant tissues, cell division, plant movements and plant aging; cytokinins help transport nutrients, regulate cell division and inhibit ageing of plant tissues, whilst gibberellins regulate growth and stem elongation, germination, dormancy and seed production and germination.
Amino Acids
There are twenty amino acids that form the building blocks of protein. In good conditions, plants can usually produce all the amino acids required but, when under stress due low cutting height, poor light and drought, photosynthesis is inhibited and amino acid production reduced at a time when more is needed. Amino acids tend to give the best results for turfgrass, applied during the early spring when the plant finds it hard to produce the proteins needed to start growth after the winter, and during times of heat and drought stress in summer. Amino acids are also a source of nitrogen.
Molasses Fish hydrolysate comes into its own when broken down “
Molasses is an extract of sugar cane and is available in many forms, but when used on turf grass it is usually best to use the complex carbohydrates produced after the simple sugars and salts have been extracted in the production process.
Fish hydrolysate is basically the parts of the fish not used for human
consumption, with the bones degraded by enzymes, though for turf use products that do not smell of fish should be used
Its primary function as a biostimulant is a food source providing carbon, sugars and carbohydrates for soil microbes, particularly bacteria. Most molasses based products also contain a quantity of trace elements which are also used by soil microbes that require trace minerals to act as catalysts to produce enzymes that make nutrient available to plants.
Molasses also works as a chelating agent to convert the soil’s tied-up nutrients into a form that is easily available to plants. Chelated minerals can be absorbed directly into the plant, so it is a good idea to add a complex carbohydrate and fulvic acid to liquid inorganic fertilisers to improve fertiliser uptake and efficiency and help the nutrient remain available and stable in the soil.
Molasses and concentrated molasses solubles give best results when applied in spring to get needed carbohydrate
132 I PC DECEMBER/JANUARY 2016
into the plant and as a plant nutrient and soil microbe biostimulant in summer.
Care should be taken when applying it in autumn, or at times of high disease pressure because, if applied onto newly active fusarium or other diseases, it may be used as a food source by the fusarium before the beneficial microbes can use it for their own growth.
Fish Hydrolysate
Fish hydrolysate is basically the parts of the fish not used for human consumption, with the bones degraded by enzymes, though for turf use products that do not smell of fish should be used. Whilst fish hydrolysate contains NPK when used in small quantities as a biostimulant, the nutrient content is negligible. It is as a microbial feed that it comes into its own and, when broken down, its high protein content is good for increasing protein in the plant in times of stress.
Fish Hydrolysate is another good cool season growth promoter that can be used through out the growing season.
Oxygen
The above compounds are the base raw materials for most biostimulants, and most of the products available to turf managers contain one or more of these products. But it is important to remember that all beneficial soil microbe and rootzone plant growth promotion takes place in aerobic conditions, which means that oxygen is the best biostimulant. Frequent aeration with microtines or sarrell rollers is essential for any biostimulant to work on a frequently compacted rootzone. However, there are now liquid products available that can be sprayed over the surface to release oxygen atoms to support even microbial metabolism and, in my next article, I will look at how soil microbes, biostimulants and frequent solid tine aeration may end the need for aggressive hollow coring and thatch removal.
Hopefully, this article will help managers to use the correct biostimulant to achieve the desired results. Biostimulant use is a very well researched topic and there is a wealth of information available for further study. Knowing which biostimulant to use, and when to apply it, can really improve conditions and reduce costs by improving nutrient and oxygen availability and uptake, disease resistance, soil friability and water retention.
Symbio is dedicated to researching solutions to restoring the natural biological activity in soils and growing media essential to ensure the long term sustainability of food production and amenity plant resources for the world’s increasing population.
www.symbio.co.uk
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