Soil additives – which way to go

More and more is expected of golf courses today. Stress increases with play on wet soils, increasing all-year round use, added fixtures, close mowing, removal of grass cuttings and moisture and temperature extremes. Hence the performance of the golf green is becoming increasingly dependent upon frequency and degree in a standard routine maintenance programme. What this means varies with course managers and unfortunately much depends on the annual budget available.

Now included as standard are extra inputs incorporating better aeration, a revised approach to nutrition and an ever-increasing number of supplements both of organic and inorganic origin. The demands made on golf courses have encouraged commercial production of an array of organic products including organic fertiliser formulations, biotic stimulants, soil conditioners, humic substances, amino acid formulations, microbial and enzyme innoculants and micorrhizal fungi – all seemingly well researched and soundly promoted based on scientific facts. This wide variety of products brings confusion to many a course manager – so which way does he/she go?

Why is there the need?

Situations have simply arisen where there has been an inability or failure to sustain suitable physical and chemical conditions for healthy microbial activity and properly nourished grass growth.

The symptoms are there for all to see in poor moisture penetration, faster meadowgrass encroachment, excessive thatch and organic matter, black layer accumulations, weak top and root growth, greater dependency on fungicides to control disease, reliance on high levels of nutrition and poor drainage performance.

This may appear damming and all the symptoms are not normally present together, but few golf courses do not exhibit any of these shortfalls. Notwithstanding the added stress to grass cover, these conditions are generally due to the absence of a systematic and structured maintenance programme and/or inheriting physical and environmental conditions that severely restrict performance and over which little can be done.

Surely, the first step must be to go back to the basics. A specific audit or factual assessment brings to light the magnitude of the weakness(es): physical analysis of the rootzone, grass cover density, root depth and density, compaction, depth of thatch, organic matter content in the top 100mm, drainage design (surface and underground), water infiltration rate, water holding capacity, hydraulic conductivity, degree of shade and barriers to air circulation, form and degree of aeration treatments and the basic nutritional status of the rootzone.

The reasons may or may not be readily apparent, but with determination many of the factors can be improved with persistent effort – in many cases without applying additives.

Inorganic and organic

The turfgrass plant is one of the greatest organic matter producers in the top 50mm of the soil. It is primarily dependant on the availability of essential mineral nutrients in the soil solution to ensure uptake by the roots. In the presence of an adequate oxygen supply, a vast beneficial microbial population develops naturally in the organic soil, giving rise to many of the essential nutrients and organic substances now commercially available.

Tom Bruulsema of the Potash and Phosphate Institute recently stated, “Commercial fertilisers supply nutrients in the inorganic form – the form that plants actually absorb – to boost the growth of plants. Plants are the only original producers of organic materials that structure and cover the soil and feed its organisms. So inorganic nutrients are vital to the ecology and health of the soil ecosystem.”

It is clear that the mineral nutrient supply from organic matter in the soil goes a long way to provide plant nutrition. Any deficiencies existing in the soil or arising from the removal of grass cuttings must be supplemented in inorganic form either in the form of commercial fertilisers or selective organic products containing these minerals.

Every golf course is different. In the region of 70 hectares there is a wide range of circumstances occurring, all of which exhibit factors that can have a significant affect on maintenance requirements. Only a fool does not listen to a genuine sales promotion – or to anyone offering comment. Acceptance of what is offered is another matter – but some remedies are sure to give promise of improvement. A golf course offers ample scope to try out a treatment or remedy that shows interest but including a control area in the same location is vital if a meaningful comparison is to be made of the benefit.

Now attracting more attention are microbial innoculants, micorrhizal fungi, amino and fulvic acids, zeolite and compost tea. One or other are ascribed to improve the microbial performance in the rootzone, increase root growth, restrict mineral leaching from the rootzone, reduce the occurrence of disease and make better availability of existing minerals in the soil so reducing fertiliser requirements. Yet so often treatments are judged without any consideration of the physical, chemical and weather conditions at the time. Unreliable judgement is certain to follow when a treatment is not properly evaluated relative to the prevailing conditions and a control treatment.

Balanced nutrition

Though standard NPK formulations are generally used many managers are unaware of the cumulative application of relevant minerals and see little need for periodic soil analysis. There are established ‘sufficiency levels’ of dependable mineral nutrients in the soil below which plants will respond to added fertilisers and above which they will not respond. This basis in making recommendations is generally accepted but an alternative approach aimed at creating ideal ratios between calcium, potassium and magnesium content in the soil solution is receiving wider acclaim. These approaches can lead to significantly different recommendations which again becomes confusing to many.

With the overall objective to reduce the amounts of mineral nutrients applied – especially nitrogen – and the use of chemicals, trials with appropriate organic additives have their worth particularly if circumstances warrant their use. However the first move surely must be to reinstate optimum physical conditions and ensure a balanced nutrition supply of the main mineral elements is available to the plant amidst a thriving microbial population and within a well-drained environment.

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