In protecting ourselves against pathogen attack we leave ourselves open to harm from the very substances used for defence
at alternatives for producing and managing high quality playing surfaces. Many are looking at, and actively trialling, a more organic, or environmentally sensitive, approach. Brews of
compost tea, seaweed and carbon based materials are all being tried and
drawn criticism from some quarters as being of the ‘green’ fringes of turf care, but this is consistent with general criticisms of organic land management. This article briefly highlights
some history of the organic management of land, and also outlines some of the research currently going on into alternative turfgrass nutrition practices
By Andrew Turnbull BSc Hons evaluated. This has also
With the cost of fertiliser rocketing this year, many turf managers are looking
The Law of the Minimum
Justus von Liebig, a famous agricultural chemist, is usually credited with having first published (1840) the concept of the Law of the Minimum, but the essence of the law, in reference to soil fertility, was first conceived by Carl Sprengel around 1828.
The Law of the Minimum is an ecological principle that considers the proper balance among factors required for the growth of a living organism. If, for example, plant growth is constrained because phosphorus is the most limiting factor, adding more of some other less-limiting nutrient will not increase plant growth until the need for phosphorus is satisfied. Even when other nutrients are in good supply, plant growth will not be greater than the amount permitted by the level of available phosphorus.
An analogy used to illustrate the Law of the Minimum concept is that of a barrel in which each individual stave is a soil mineral. The lowest stave will cause water to leak from the barrel, which needs to be topped back up to stop the barrel emptying. The research of Carl Sprengel showed that a major benefit of humus to soil fertility was that it could supply mineral nutrients to plants but, at the same time, plants could be grown without humus if the necessary inorganic minerals were supplied. Once it became known that plants could be grown without soil organic
matter, or humus, so long as there was an adequate supply of all essential mineral nutrients, Liebig used his fame as a chemist to devalue the important role of humus to soil fertility and promote inorganic mineral fertilisers as all that was necessary.
The Law of Return
The Law of Return was a teaching principle that Sir Albert Howard (1873- 1947) used to encourage the adoption of farming practices that would follow nature’s example of recycling all natural and organic waste products back to the soil. Howard was a mycologist who worked as a research agriculturist and is regarded, by most, as the founder and pioneer of the organic movement.
Drawing on his many years of agricultural research experience, he wrote several widely read books espousing his concepts and theories of composting, soil fertility, and health and disease. In 1943, he published the book, An Agricultural Testament, in which he described a concept that was to become central to organic farming - the importance of utilising available waste materials to build and maintain soil fertility and humus content. According to what he called “the Law of Return” he strongly advocated the recycling of all organic waste materials, including sewage sludge, back to farmland. Howard’s concept of soil fertility was
SOIL Biology or Chemistry?
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