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Winter soil testing for turf

Winter is an ideal time to have your soil tested. Before things get hectic in spring, now is the time to plan for turf renovation. It’s the best time for your laboratory, too, because testing work slows down in winter. You’ll get your results faster too.

Many turf managers worry that winter is too early for testing, and wait until spring before sending off their samples. This has the disadvantage that they squeeze themselves out of enough time to get the best turf results. Surprisingly, soil characteristics (pH, salinity, organic matter content, CEC and so on) change only slowly over a timescale of months (even though they can change rapidly from day to day). So testing in winter will return virtually the same results you’d get in spring, only you get them back faster and with plenty of lead time to plan. You also get the opportunity to shop around and get the best price for the materials the testing has identified as needed.

Renovating

Conventionally, sports turf is renovated in late winter to early spring – around August–September in NSW. This is a very narrow window of opportunity in which to scarify and remove the thatch (to reduce disease, sponginess, water-repellency and water retention), core the soil, topdress and fertilise before the changeover of sports codes or the return of players after the cold weather. Ideally you need 6 weeks; often you have only 1 or 2. In this situation, being ready with your soil test results well before time is essential.

The role of soil testing

Renovating is the time to add fertiliser, topdressings and ameliorants, but how much and what? This is what a soil test can help you decide. Rather than tell you how much fertiliser to apply, the role of soil testing is to help ensure that the soil properties remain within the correct range so that a feeding program has the best chance of giving good results. Keep in mind that the mere presence of a nutrient in the soil is not a guarantee that the turf will be able to take it up – the pH could be preventing this, for example. A soil test shows where soil properties need to be adjusted with ameliorants such as lime, gypsum or acidifying agents to optimise nutrient availability.

Collecting samples for chemical analysis

1. Divide the ground off into management units – any area which has been treated in the same manner and has the same or similar soil properties. It could be a green, a fairway, or half an oval with a different soil type from the other half.
2. Use a spade or sampling corer to take subsamples from 0 to say 100 mm – but always the same depth.
3. From each management unit, take 6 to 12 equal-sized subsamples and combine them. Take 6 in a very uniform management unit such as a sand table green, up to 12 in a natural soil, which is inherently more variable.
4. Remove turf and thatch, being careful not to lose too much soil.
5. Break up the combined cores and thoroughly mix them in a plastic bag.
6. Take out about 200 g (2 cupfuls) to send to your preferred laboratory.

Collecting samples for physical analysis

Taking samples for physical analysis is very different. Permeability, infiltration rate and density have to be tested in undisturbed soil cores, preferably in the field. If you are not confident that you can get an unbroken sample to your laboratory, call the lab and arrange for someone to visit you.

Fertiliser program

Designing a fertiliser program needs comprehensive information on climate, cultivars, expectations of the field, past fertiliser history and response, foliar analysis, the longer-term reaction of the soil to the fertiliser program (e.g. is it acidifying?) and a good knowledge of the release characteristics of the fertiliser. Developing fertiliser programs requires an integrated approach using actual growth observations, soil and leaf analysis, and a skilled and experienced interpreter. Some labs (usually fertiliser labs) use special software to recommend fertilisers (usually their own). But given that soil testing cannot predict nutrient requirements, this approach is of doubtful utility. The best solution is for an experienced turf consultant or analyst to use the combined information to produce an integrated soil management program. This may or may not involve changes to your fertiliser program.

Retesting after amending

A month or two after your spring renovation, consider having your soil retested. If your maintenance program is on track, the results will show this. If not, they will indicate where improvements are still needed.

Keep records

The longer you can keep records of the management of your turf, the better: Building up a history of soil test results, topdressings, fertiliser applications and so on allows any turf consultant to interpret the long-term response of the field to management and to identify any gradual changes such as acidification or salinisation.