Gypsum improves and maintains the health and hardwearing properties of all amenity turfs. It helps in two ways. It improves soil structure and it supplies calcium and sulphur, both essential plant nutrients.
The most significant problem for managers of most amenity turfs is the compaction of the underlying soil that arises from heavy foot traffic. A compacted soil leads to slow growth and slow growth means slow recovery from traffic damage – a vicious circle. There are a number of reasons why soil compaction slows plant growth. Root penetration is impeded (mechanically), drainage is reduced (in wet weather the surface is prone to flooding and the soil becomes anaerobic) and, in the summer, rain and irrigation water tends to runs off (rather than to penetrate through to the roots leading to earlier onset drought). In addition, during winter, a turf prone to waterlogging is less resistant to scuffing as it regains firmness more slowly after rainfall so that foot-traffic and mower damage is exacerbated.
Gypsum is well known to improve soil structure and drainage and to alleviate compaction so its regular use with turf reduces many of these problems. Gypsum is best applied following physical soil-aeration treatments (coring, verti-draining, vibra-moling etc) but can be sprinkled on at any time. As the pH of gypsum is neutral, excessive applications are not damaging so rates can be quite high – especially in areas having particularly acute soil problems.
Regular gypsum applications can minimise the ingress of shallow rooting Poa grasses and weed species. For new or existing turf areas, sprinkle ½-1 kg per square metre but for a heavy-clay soil up to 2 kg per square metre may be applied. Conveniently, 1 kg of gypsum has a volume of about 1 litre so it may be easier to use a volume measure, especially where spot treatment is being carried out.
Rapid growth for high health and quick repair means that the nutritional needs of the turf should be supplied. Gypsum is a good source of the plant nutrients, sulphur and calcium. Golf Course Sulphur is important for the production of green, protein-rich, leaves while calcium is important for plant health. The levels of both are high in leaves so are regularly removed from the sward by mowing. Used as a fertiliser, application rates will be lower than when used to remedy a severe soil condition (closer to 1 kg/2m2 each year). If, instead, gypsum is broadcast onto the turf surface at regular intervals during the year at about 1 kg/5m2, advantage is taken of the electrolyte effect of gypsum. This minimises the dispersion of clay particles but lasts only while the gypsum is present on the surface.
Gypsum increases soil microbial activity and encourages worms, speeding up the decomposition of organic matter. Where clippings are mulched and left on the turf rather than being removed, regular applications of gypsum will help speed up their breakdown and the eventual return of organic matter and nutrients to the soil.
It is difficult to exclude small children and wildlife from public areas so management should employ ‘friendly’ methods wherever possible. Gypsum is a natural, non-toxic mineral that is certified for use in organic production. Even when applied at very high levels it will not damage animals, soil or plants. Also, gypsum’s neutral pH means that where it is used in parks for high-traffic areas of turf lying close to rhododendrons and camellias it will not raise soil pH and so damage these acid-loving plants (lime would).
Application of gypsum to turf improves:
Playability of winter sports fields
Trafficability of lawns (especially after rain)
Durability of racetracks
Seedbed conditions for new turf
Efficiency of irrigation
Oxygen supply to roots
Plant health, growth and repair rates.