... I tell them it’s the other way round, “the greenkeeper made holes in the greens and then they were brilliant”
couldn’t all be 10,000. They agreed the levels could not all be the same. As they measured up to 10,000, and all the samples exceeded this level, they had shown them all to be the same! Further research showed that the greens had been built on crushed shells from the cockle industry. These shells, whilst being virtually pure calcium, are insoluble, so the levels were not harmful to the turf. In fact, they assisted with providing a high quality free draining surface.
The additional testing that we did on this occasion included a soluble paste test, whereby a paste is made with the rootzone and the irrigation water from the site. This is then tested to see what is soluble and, therefore, available to the plant. The calcium was not soluble, and a leaf tissue analysis showed a deficiency within the plant. Again, this was not the course manager’s fault and it was easy to resolve.
Justus von Liebigs drum
As explained in the preceding article, Justus Von Liebig, generally credited as “the father of the fertiliser industry” formulated the law of the minimum. If one nutrient is missing or deficient, plant growth will be poor, even if the other elements are abundant. Liebig likens the potential of the plant
barrel with staves of unequal length, the capacity of this barrel is limited by the length of the shortest stave (in this case phosphorus) and can only be increased by lengthening that stave. When that stave is lengthened, another one becomes the limiting factor.
The deficiency tests at Yara
In trials conducted by Yara UK, a global plant nutrition company, on dwarf rye, each pot was deprived of a different nutrient (as shown in the images). This shows in a graphic way that shortages of nitrogen, potassium, sulphur and magnesium had the most dramatic effect, but a shortage of any nutrient had an impact.
What they all do
pH - Knowing the pH level is an essential aspect of managing turf. The finer grass varieties, such as fescues and bents, require an acidic rootzone of around 6. However, if the rootzone becomes too acidic, it will start to affect the availability of the nutrients. At a pH of 4-4.5, the availability of nitrogen, phosphorus, potassium, sulphur, calcium, magnesium, manganese, boron, copper, zinc and molybdenum are all reduced.
cec - This is the abbreviation for cation exchange capacity, the measure of the rootzones ability to store nutrient. A clay or organic soil will have a high cec of up to 20; a sandy soil will have a cec as low as 2 or 3.
Many turf managers ask me “What is the optimum cec?”. There is no ideal cec, there is only the cec that you have, and you must work with that level. So, if your cec is low, feed little and often. There are several ways of increasing your cec, which will increase the benefit you receive from your applied nutrition as less will leach. Organic matter and clay are the main methods of increasing the cec, however, it is important that you do not adversely affect the drainage by applying the wrong solution. The most commonly used methods of increasing cec are shown in the table below.
Product
Organic matter Seaweed
Clay Granule Zeolite
Improvement Short/medium Short/medium Long term
Long term
Organic matter - Extensive research has been conducted as to the optimum levels of organic matter. The majority of this research indicates that a level of 5% is correct.
My own opinion on this is that a level of 5% is ideal in Florida where most of the research has taken place but, for the United Kingdom, the level should be between 3 and 4%. The reason for the difference is that the
microbial activity in the soil is far greater in Florida due to the higher temperatures there than in the UK. The increased microbial activity breaks down the organic matter. If the levels are allowed to increase too high, this will increase the thatch and provide an environment where disease can flourish.
Nitrogen (N) - Nitrogen is a unique element, as optimum levels should vary dependent on the season. Nitrogen is required for topical growth within the plant and is such an essential nutrient because, without growth, you cannot get recovery from damage. It is also impossible to achieve a ‘surface’ without growth. The levels in the spring and summer should be greater when the plant is more actively growing. Nitrogen is probably the most used and abused nutrient in turf management, and the following factors should be remembered when specifying your fertiliser:
• There are four main sources of nitrogen - nitrate NO³, ammonia NH³, urea (NH2
)2CO and methylene urea • The plant only takes up nitrogen through the roots in the form of nitrate
• All forms of nitrogen, other than nitrate, have to break down to nitrate before they can be taken up by the plant, this is what leads to the different release times of different fertilisers
• The release times of the main sources of nitrogen are: nitrate - four weeks, ammonia - six weeks, urea - ten weeks and methylene urea - twenty weeks
• Nitrate is acidic, as are most forms of ammonia. Sulphate of ammonia will form sulphuric acid. Urea is slightly alkaline
Application Easy Easy
More complex More complex Comments
Can reduce drainage Also contains nutrients
May break down and harm drainage
Does not break down
If a fertiliser contains high levels of nitrate it will have high impact, but it will not last as long as a fertiliser that contains high levels of urea.
When the dormant season is
approaching, I will always recommend a fertiliser that is reasonably rapid release as this will ensure that, if the weather turns cold, there is not unreleased nitrogen in the soil that could be released if a warm period occurs during the winter. The choice of form of nitrogen can benefit the turf in other ways. If you have a potassium deficiency, opt for potassium nitrate as you will be getting two benefits in one. Conversely, if you have a black layer issue, caused by high levels of sulphur and iron, avoid the use of sulphate of ammonia as this contains sulphur and will make the problem worse.
As a general point, plants cannot absorb granules, they can only take up liquids, so ALL fertilisers are liquid but some are applied in the form of a granule.
Phosphorus (P) - Phosphorus is required for root development in both mass and length. It is also involved in the process of photosynthesis. Other benefits that the plant achieves from phosphorus include an increased ability to withstand stress. Phosphorus is, however, very insoluble and does not move freely within the soil. A plant can only draw phosphorus from 1mm away so, if the plant has poor root development, it cannot locate and absorb the phosphorus. Therefore, it cannot develop roots and you end up with a vicious circle which results in poor root development. If this problem occurs I would
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