Best Technical Merit Award Answers- October 2003
Following the success of the Technical Merit Award 2003, sponsored by Tillers Turf. Pitchcare have been publishing some of the best answers submitted to the monthly scenario questions. Here are the best of the October answers. Next week the final November question will be published with the best answers provided by members.
October Scenario question
Soil pH can determine the choice of sport played; as turf grass species enjoy differing pHs, explain how pH tolerance and preference will affect the establishment, growth and recovery of different grasses suitable for use on sports surfaces.
Answer 1) Introduction: Turfgrass sports surfaces have different demands on them depending on the individual requirements for the sport being played. Achieving these demands and meeting the requirements vary from site to site, due to the localised growing conditions in which the sports are being played. Soil pH is one variable that may affect the turf management of individual sites, because it may influence the type of grasses grown to achieve the desired results, such as; optimum growth rates.
Soil pH causes changes in the soil that can affect growth, such as:
- Affecting nutrient availability for plant growth
- Increasing acidity, which causes a build-up of toxic Al 3+ (particularly at a low pH)
- Affecting the number and type of organisms in the soil environment.
Turfgrass growth: Most of the grasses in the UK will grow in varying conditions, but generally grasses are more successful growing in their own native environment. The most suitable pH for any site was once described as the one you've got! So any grasses that are already growing on the site are more likely to tolerate the ground conditions, including the pH.
Grasses, over a long period of time have adapted to their own local conditions, some grasses have adapted to the sandy soils of the coast with a low pH, low moisture and low fertility, whilst other grass species have adapted to inland heavier soils, with a neutral pH and higher fertility.
Bents and fescues are fine leaved grasses that can grow in a variety of soil conditions, but they appear to have adapted better to the sandy high pH conditions of the coastal links, which accommodate such sports as golf. Bents and fescues can thrive at low pH levels because they have adapted to them.
Low pH causes many nutrients to be leached from the soil, so successful grasses in this soil have adapted to be more efficient with nutrition. The other adaptations may include a greater tolerance to Al 3+; an element that becomes harmful to plants at low a pH. Winter games are generally played on harder wearing swards made up of such grass species as; timothy, perennial ryegrass, rough stalked meadow grass and smooth stalked meadow grass, which have adapted to living on heavier more fertile inland soils, with a pH at or just below neutral.
Perennial ryegrass is a common grass species found in the UK, but is more indigenous to the pastures and meadows, of what would now be considered as parkland golf courses, and rich farmland. These soils contain a higher percentage of clay than the more sandy soils found on the links. Clay particles in a soil can buffer pH levels; this means that a large quantity of acidic material would need to be applied to lower the pH significantly to affect growth.
Other benefits of clay soils are increased nutrient availability and moisture retention. Grasses that have adapted to these conditions are less-drought tolerant, require more nutrients, and are less successful at extremes of pH. These grasses do have advantages though, one of these is that they appear to tolerate damper conditions than bents and fescues, and are generally considered to be better at coping with wear and compaction. Annual meadow grass is a very common turfgrass weed that can thrive in many different types of soils, however their growth rates are encouraged by fertile, well irrigated, neutral to alkaline soil conditions.
Turfgrass management practices should be tailored to discourage the development of annual meadow grass in the sward, whilst still maintaining a high quality grass sward for sport.
Turfgrass establishment: It is possible for turfgrass managers to establish and grow grass species in conditions that would not normally allow for their optimum growth. Turfgrass maintenance programs can be tailored to particular grasses to increase their growth rates and provide better performance characteristics for the sport being played. Management techniques such as regular soil analysis and subsequent fertilising can assist ryegrasses to perform better on soils with a low pH, whilst a program of regular aeration and the careful application of fertilisers will encourage bents and fescues over more undesirable swards grown on heavier soils.
Turfgrass recovery: To aid and encourage the growth and recovery of bent and fescue turfgrass on sandy soils with a low pH, it may be advisable to fertilise on a little and often basis with a fertiliser that at the very least contains some nitrogen. This is because nitrogen in the form of nitrate is most easily lost from this type of soil. Swards containing perennial ryegrass will require a greater input of nutrients and irrigation water to aid recovery on sandy soils. It may also be advisable to use materials on the site that are not acidic, and therefore increase the acidity further. The recovery of grass species on heavier soils is best achieved with regular aeration. Bents and fescues are more sensitive to compacted soil conditions, so a regular program of aeration may need to be implemented to reduce or control compaction. Coarser grasses and weed grasses may be encouraged by compacted soil conditions, as they may be more suited to them, so a program of regular aeration may help to control these weed species.
Contamination: The pH can be high because of Calcium, but also Sodium. Sodium a constituent of salt is very bad for soils as it causes deflocculation (loss of structure to clay particles) and reverse osmosis. Sodium contamination can result due to coastal spray drift, and using cheaper, unwashed and contaminated sands.
When doing a pH test it is important on new areas to determine whether the excess alkalinity is caused by either of the elements. Treatment for sodium contamination is different than for soils with high calcium contents, and the identification of the problem element is vital for implementing the correct management technique.
Summary: Soil pH is only one of many variables that can affect turfgrass growth, and the quality of the surfaces that turfgrass managers produce. Measuring the soil pH is just one of many management techniques that can be carried out to aid the identification and implementation of a suitable turfgrass management system, that provides quality sports surfaces. "Change the management of the soil, not the soil to the management!"
Answer 2) Acidic soils have a low pH (potential Hydrogen) such as leached heath land sands, neutral soils have a pH of 7.0, and alkaline soils which can be chalky or high in certain clays have a high pH. PH is on a logarithmic scale, so that a pH of 8.0 means a soil is 10 times more alkaline than neutral and a pH of 9.0 is 100 times more alkaline.
The effect of pH on turf is primarily that it controls the availability of nutrients to the plant from the soil. The pH affects the solubility of mineral salts, and influences Cation Exchange Capacity in the soil, and therefore determines the availability to the plant of important nutrients.
In acidic soils the major nutrients N, P and K become increasingly unavailable; P availability declines most rapidly and is limited below pH 6.0; Ca and Mg also decline, typically because lime and related minerals dissolve and leach out in acidic conditions. In very acid soils Al can be present in toxic levels because it is very soluble at low pH. In alkaline soils P availability declines slowly as pH rises, but Mn (Manganese) is limited above pH 7.5 and Fe and Cu availability also decline.
The general rule is that most plants prefer a soil, which is slightly acidic, around pH 6.5 - this holds true for soils with a low organic content, e.g. less than 5%, but curiously for the same plants the optimum pH in peat is more acidic at around 5.8 due to its differing CEC and buffering behaviour.
The root zone of a cricket pitch table should be very low in organic content, e.g. no thatch, while it can be higher on outfields, golf courses etc but should still be quite low (for stability, drainage etc). Despite the general rule, different plants including grass species prefer slightly different pH conditions. All other things being equal, the establishment, growth and recovery of a plant is driven by root performance.
The performance of the root, which acquires water and nutrients, is catalysed by the symbiotic relationship between Mycorrhiza and the root hair itself. Mycorrhizas are fungi, which multiply the absorption and transport capability of the root hair system. Almost all plants depend on them, and fortunately there are millions of them in the soil. Each plant can require a specific mycorrhizal association for best performance, and the catalytic effect of each Mycorrhiza can have a specific optimum pH level. For example, most rye grass (Lolium perenne) cultivars prefer acidic conditions in the range pH 5.5-6.5, as do many bent and fescue grass varieties; whereas annual meadow grass Poa annua, other weeds and mosses prefer a higher pH. Maintaining a more optimum, typically lower pH will therefore help sports turf to compete better with unwanted species.
If you know the optimum pH for your grass species and cultivar, and provide that pH, you give it the best chance to compete, stay healthy and grow well. It is often the case that correct amounts of nutrient exist in the root zone, but are not sufficiently available to the grass due to wrong pH levels, and simply adding nutrient may help only slightly or temporarily - it isn't the right answer, modifying the pH is.
As pH is lowered the control of diseases is also improved, since fungi such as Fusarium do not like acidic conditions. Acidic conditions also limit the activity of other microorganisms, and a big bonus for cricket pitches, bowling greens and tennis courts is that acidifying the rootzone will also control earthworms. For this reason we apply sulphate of iron, because it acidifies the root zone. But!!! Don't overdo it, and do it at the right time.
Since the major nutrients NPK decline in availability below pH 6.0, acidifying in the summer could end up starving a growing turf or you may find yourself over-fertilising to try and compensate. Sulphate of Iron is commonly added in autumn when moss needs to be controlled, and at the time when the plant is becoming dormant and so its requirements for NPK have declined.
During the growing season it would be better to keep pH levels of 6-6.5. (In my opinion). You can play football, rugby etc on a pitch with a mix of bents, fescues, ryes and meadow grasses so if the soil is a bit alkaline it won't matter too much, even though a dominant percentage of rye is preferred. But cricket must be played on a table, which is dominated by fine tufted grass, rye and sometimes fescue and bent, these days we go for 100% rye. And fine turf for golf and bowling greens typically uses a fescue/bent mix. The soils here must be at least slightly acidic.