Seaweed is often used as a soil conditioner or fertiliser in the world of gardening. The range of benefits it brings are so great, though, that it’s a great addition to any plant growing activity. Seaweed contains a huge amount of minerals and trace elements and brings with it with numerous bio stimulants.
Seaweed can be used as a fertiliser or soil conditioner in many forms. It can be dug into your soil straight off the beach, or it can be dried and granulated or powdered. You can even extract the goodness from seaweed to form a concentrated fertlising liquid. In modern fertilizer use liquid seaweed makes a highly efficient base for the nutrition of a wide variety of plants as it can be safely mixed with most of the commonly used sources of nitrogen, phosphate and pottassium, along with supplements like iron.
The seaweed stimulates the soil bacteria which helps release much of the nutrient content which is in many cases fixed in the soil and not available to the plants, whether it is grass, tomatoes, vegetables or flowers, to make the most of any nutrients being applied, reducing the quantity required for healthy growth. The seaweed is also valuable in helping to break down organic matter, particularly in turf where thatch can be a serious problem if not managed properly.
Creating Your Own Seaweed Compost
The seaweed collected was used to build large heaps as pictured below, with a layer of seaweed around thirty cms thick, then a layer of our own dune sand around ten cms thick. These layers were repeated until the heap was around two metres high. Each heap was then turned over four times in the following year, then taken into the first of the three composting bays to dry out.
After a few weeks of drying the compost was then put through the Royer shredder, straight into the second bay and left for a further few weeks before the final step of screening into the third bay. At this stage it was ready for use as a nutritious compost for topdressing and for divotting. Fantastic material prepared from beach collection to usable form in just over a year.
Seaweed contains a wide range of nutrients and trace elements, along with alginates, which combine in such a unique manner that when seaweed is added to heavy clay soils it acts as a floculator, which means it breaks down the heavy soil into a friable crumb structure thus providing a vastly improved free draining growing medium. This, of course, does not happen overnight but is one of the greatest benefits of long term applications on these types of soils.
On the other side of the coin seaweed is an excellent addition to sandy soils, adding to the humous content and nutrient levels, and increasing drought resistance. Because of my experience I do believe in fact that adding seaweed to the rootzone mix in any USGA green construction does alleviate the many problems, such as take-all patch and nematode discolouration, that are inherent in a high sand content material because of the lack of a healthy microbial and bacterial population.
Raw seaweed should only be used in situations where it can be dug directly into the soil. For example it is fantastic with potatoes, giving a great flavour, and has the added advantage that the iodene content in the seaweed prevents diseases such as scab. The salt content is minimal and so it does not add a salty flavour to any vegetables.
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Duncan Gray is a lawn and turf care expert with 30 years of experience in the grass care and golf greenkeeping industry. He now runs Lawns For You, a specialist lawn care company based in Scotland and sells lawn fertliser and other products in the Lawns For You shop.