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By Jerry Spencer in {CATEGORY} on 24 Aug 2012

Part 2 of Jerry Spencers Nutrition of Sand Greens
To read the first part click Here - www.pitchcare.com.au/magazine/article/756

Grass species
Not all grasses are the same and in the turf industry the choice can be either warm or cool season grasses depending on the situation of the site.

Cool season grasses include bent grass; perennial ryegrass and fescue grasses and these have differing nutrient and pH demands in contrast to the warm season grasses such as couch grass or kikuyu.

Table 2. Characteristics of common Australian turf grass species

This can be further demonstrated by looking at the actual N requirements per 100m2/growing month although this will also vary depending on time of year etc.

Table 3. Cool season grasses. N requirements g per 100m2/growing month (Carrow et al, 2001)

These differences extend beyond nitrogen as differeing grasses have differing requirements. For example perennial ryegrass has a much greater requirement for phosphate than browntop bent or fine leaved fescues. (STRI,1996).

The role of pH also plays an important role. Different species prefer different pH levels and in conjunction with this different fertilisers have differing effects on soil pH.

Table 5. Optimal pH ranges for common Australian turf grass species

These effects will be exaggerated on the pure sand constructed areas that you possess and have a low buffering capacity.

Table 6. Liming/acidifying properties of common fertilisers

MATERIAL	NITROGEN %	CACO3 EQUIVALENT PER 9KG OF NITROGEN
UREA	45	-16.4
AMMONIUM NITRATE (NITRAM)	33.	-16.4
AMMONIUM SULPHATE	20.5	-16.4
C.A.N	20.5	0
MAP	11	-48.6
DAP	18-21	-32.3
POTASSIUM NITRATE	14	+16.4
MAP	48	-9.5
DAP	46-54	-12.7
POTASSIUM CHLORIDE	60-62	Neutral
POTASSIUM SULPHATE	50-53	Neutral
POTASSIUM NITRATE	44-46	+5

In Table 6 a minus sign indicates that the material tends to acidify the soil and a positive sign indicates that the material is basic and use will increase soil pH over time.

Cool season grasses achieve optimal growth within the range of 16-24C and are severely restricted by periods of prolonged or severe high temperature or drought.

Nature of the rooting medium
Sandy soils have very little in the way of inherent nutrient reserves. The very nature of the AGCSA specification for greens construction is that it drains extremely well and contains a minimal amount of organic matter. This characteristic further means that they are actually unable to retain soluble nutrients derived from fertilisers. The high rate of leaching means that nitrates, potassium and ammonium tend to pass through the profile into the underlying drainage water.

Soil nutrient status
Regularly soil tests are carried out in order to determine the nutrient status of your greens and this is especially important in the early days when you are attempting to establish the turf surface.

Timing of fertiliser applications
This is crucial and has a huge influence on the programme to adopt. Basically the considerations can be divided into pre and post establishment.
Map 1 shows the range of climatic zones within Australia. It can be seen that a wide range of macro and microclimates exist and these all have a direct influence.

Canberra can be classified as being in the cool temperate zone having mild/warm summers and cold winters.

Establishment
Once an area has been satisfactorily prepared the nutritional regime must be aimed at establishing a strong, vigorous sward as quickly as possible. Unfortunately this is a time where commonly turf managers fail to apply enough nitrogen and as a result see poor establishment.
For quicker establishment of 'Crenshaw' creeping bentgrass, liquid fertilizers tended to work better than the granular fertilizer. However, quality was highest at the end of the growing season for plants treated with the granular product. Plants grown on plots treated with lighter, more frequent applications provided higher visual quality ratings. This could be attributed to the higher N, P, S, Mo, and Zn concentrations in tissue of plants grown on plots treated eight times per month compared to those treated only twice (Michael B. Faust, Nick E. Christians, and Barbara R. Bingaman, 1998)
In the case of constructions with a high percentage of sand the initial problem is one of moisture retention. In order to overcome this organic amendments are added such as peat moss or poultry manure. Problems exist with both of these.

Peat moss is acidic possessing a pH of 4.5 and takes a considerable time to breakdown. Consequently if this is not incorporated thoroughly throughout the profile it can lead to a build up of a highly moisture retentive layer at depth and so encourage anaerobic soil conditions to develop.

An analysis of poultry manure shows that it does in fact contain low levels of organic matter and also can contain sodium in worrying levels depending on the source of manure. Preferable to both of these options is dried seaweed, composted sewage sludge or humic acid derivatives.

In relation to nutritional benefits from these amendments it is unlikely that these alone will lead to optimal growth of the respective grass species. To achieve this additional nutrients have to be added. Zontek (1990) showed that new sand based constructions required 500gN/100m2 in a soluble form and 500g N/100m2 in a slow release form to achieve optimal growth. If using soluble nitrogen sources other rates suggested are around 450g N/100m2 every 10-14 days (Davis. 1973).

Bearing this in mind if staffing or time is an issue slow release forms of nitrogen are preferable as Nelson 1987 showed that most of the nitrogen applied in a soluble form had gone within 72 hours of application with 50% having gone within the first 24 hours.

Bentgrass
Use soil test results as a guide to determine how much starter fertilizer to incorporate into the seedbed. A rule of thumb is to incorporate a 1-2-1 ratio starter-type fertilizer at a rate of approximately 450-500gN/100m2 of turf into the upper root zone just prior to seeding. Remember too try and use fertilisers which are safe to germinating seeds and have a low salt index. (Vavrek, B, 1999)

Post Establishment Fertiliser strategies

Once established, nutrition of bentgrass greens is aimed at encouraging strong disease and stress tolerant growth exhibiting a strong and vigorous root system.

Bent responds in different ways to different nitrogen fertilisers (Skogley, 1967) and also variations in behaviour occur between cultivars. For example browntop bent favours ammonium sulphate rather than sodium nitrate.

Extensive research carried out in the UK (Escritt and Lidgate, 1964) showed that ammonium sulphate applied at an equivalent rate to 1.1 kg N/100m2 applied in three dressings, was perfectly acceptable for satisfactory growth of a mixed bent/fescue turf. However, over time the acidifying nature of the ammonium sulphate lead to a build up of thatch. This rate of 1.1 kg N/100m2 should now be regarded as a minimum rate of application, and now the application rate is more likely to be in the range of 1.1-2.0 kg N/100m2 especially with some of the newer turf cultivars on the market.

On pure sand greens Lawson (1987) proposed an annual rate of 2.5 kg/100m2 provided adequate cover.

As a general rule Penncross and Pennlinks will require around 1.5kgN/100m2/season in Canberra and the surrounding areas. These figures are supported by the figures given out by Barenbrug (2001) for Regent and Bardot. They state four applications of 500g N / 100m2 / annum.

Green and Beard (1969) looked at changes in the carbohydrate reserve of creeping bentgrass in relation to nitrogen applications and found that any one application of more than 630g N/100m2 lead to a significant decrease in leaf carbohydrate. The significance of this is that grass uses this carbohydrate to recover from wear stress and for cold tolerance over the winter. This points to the final dressing of the year therefore not exceeding 600g N/100m2.

With newer constructions the aim is to produce pure bentgrass surfaces. However, over time wintergrass will undoubtedly invade the surface and if this does occur the options then are to manage it or adopt an eradication programme. With wintergrass the key is regular light applications of nitrogen at a rate of 250gN/month as this will encourage growth and recovery without the associated lushness that occurs with heavier applications.

As discussed in the 'establishment' section the low nutrient holding capacity inherent with sand-based systems makes it difficult to provide adequate nutrition to turf.

In an attempt to deal with this some course superintendents have adopted 'spoon feeding'. This means frequent applications of liquid fertilisers at low rates. This approach offers versatility and a high degree of control. However it can be extremely labour intensive.

Liquid fertilisers have been used for this purpose as they avoid the problem of 'speckling' that can occur with granular materials. When the latter are used at low rates they can cause in irregular green dots over stimulated turf.

Research has however been carried out into dry "spoon-feeding" using low analysis granular fertilisers. These can be produced in low nitrogen concentration formulations with other nutrients incorporated into the fertiliser, such as iron and magnesium.

Tissue analysis revealed that all the solid fertiliser treatments had total nitrogen contents higher than the liquid fertiliser treatment which is not surprising when by mowing and removing leaf tissue the main access point for liquid fertilisers into the plant.

While turf grown in the solid fertiliser treatment plots can take up more nitrogen from the rootzone, no nitrogen is available to the turf grown in the liquid fertiliser plots until subsequent applications of foliar sprays are made.

Nutrient applications

Table 7. Recommended annual phosphate (P) applications (Bray P1- Extractable

SOIL TEST G/M2	GENERAL TURF KG/100M2	HIGH MAINTENANCE TURF KG/100M2
VERY LOW <0.74	1.5	2
LOW 0.79-1.22	1.0	1.5
MEDIUM 1.27-1.97	0.5	1
HIGH 2.01-3.45	0	0.5
VERY HIGH >3.45	0	0

Based on figures supplied by Michigan State University Soil testing Lab


Table 8. Recommended annual potassium (K) applications

SOIL TEST G/M2	GENERAL TURF KG/100M2	HIGH MAINTENANCE TURF KG/100M2
VERY LOW <1.4	2.0	2.5
LOW 1.4-9.4	1.5	2
MEDIUM 9.4-16.3	1	1.5
HIGH 16.3-23	0.5	1
VERY HIGH >23	0	0.5

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Read more articles in {CATEGORY}, by Jerry Spencer or from August 2012.