Fertilising your lawn can be a simple task that brings great benefits however it’s surprisingly easy to get it wrong. Homeowners and turf professionals alike tend to fall for the same four fertiliser no-nos.
Avoid these mistakes and you’ll save money, be rewarded with greener grass and fewer weeds and as a bonus you’ll be helping the environment.
1. Not knowing your soil
Understanding the type of soil that lies beneath your lawn will help you use fertilisers effectively and efficiently. Different soil types respond in different ways to fertilisers so this means you’ll need to adjust what you apply and how you apply it. To know your soil type you’ll need to dig a few small test holes to around 10cm deep and remember that the type of soil may vary from spot to spot. Soil types fall into three main categories – sandy, loam, clay – with crossover between all of them.
SANDY SOIL will clearly contain sand and tends to fall apart if you take a handful and try to squeeze it together. Although excellent under lawns as it doesn’t compact it has the highest potential to lose nutrients when you apply water as the water will run through quickly taking nutrients with it.
Reduce this by avoiding excessive watering after fertilising, using liquid fertiliser that will be absorbed through the grass leaves and regularly applying a hose-on seaweed tonic to help develop more natural organic matter in the soil by stimulating soil micro-organisms. Using an organic lawn fertiliser is good idea too for the same reason.
LOAM tends to loosely clump together when you squeeze a handful but will fall apart pretty easily afterwards. Although it is excellent soil for grass growth and water and nutrient retention it can be prone to compaction. Using a quality slow-release fertiliser or an organic-based fertiliser supplementing either with regular applications of hose-on seaweed helps to maintain good soil structure.
CLAY will stick together as a definite lump when you squeeze a handful. Will feel sticky or slimy if moistened. Clay-based soils are highly prone to compaction and this can lead to problems with grass growth and drainage. Clay soils are also often quite high in natural mineral nutrients however these nutrients can be ‘locked up’ in the soil structure. Apply hose-on gypsum, often sold as ‘clay-breaker’, to start to open the soil up and release these nutrient goodies. Use a quality slow-release fertiliser and regular applications of liquid seaweed.
pH testing
Measuring the soil acidity and alkalinity through pH testing can be useful especially if you have problems that seem unsolvable. If your lawn is growing well then there’s really no need for a pH test.
Ideal pH is around 6 to 7, if the soil is outside of this range then your lawn may not be able to access nutrients. You can buy a simple pH test kit from the nursery or hardware store. Just remember that pH can vary dramatically from one end of the lawn to the other so always test each sample individually, never mix the samples together.
If you get an extreme reading from one spot take another sample and test again.
If your soil reads as too acid, which is not unusual if old-fashioned or cheap fertilisers have been used before, then add garden lime or dolomite at the recommended rates.
If alkaline then you’ll need to look at adding sulphur. This process is trickier and potentially expensive.
Remember that any treatment required will relate to the tested area, not the entire lawn unless of-course results were consistent across the lawn.
2. Applying too much
It is very important to stick to the fertilising rates recommended and to spend a little extra money on a quality fertiliser, preferably slow-release.
If you apply too much fertiliser, especially where the soil is sandy, a fair amount of it will leach through the soil and eventually make its way into groundwater, wetlands, lakes and streams so apart from wasting money you are polluting your local environment.
Over-fertilising can also lead to surge growth, a situation where grass puts on too much growth too quickly resulting in weak grass blades and stress on the lawn by over taxing its metabolism. This also makes it more susceptible to attack from pests and diseases.
You’ll find it also means that you’ll be mowing more frequently than necessary, potentially resulting in increased soil compaction, engine exhaust and noise pollution, wear and tear on your mower not to mention extra work for you.
3. Feeding at the wrong time
If you only fertilise once a year, apply it in late winter or early spring depending on your local climate. This is when your lawn is at its hungriest after the stress of winter and will respond best to the nutrients it receives.
Fertilising at this time will help your lawn to repair itself after a long, cold winter that in most parts of the country will see grass browning off or looking patchy.
Ideally it is best to feed three times a year – late winter/early spring, mid-summer and early autumn.
If you’ve had problems with summer lawn prickles like bindii then use a suitable ‘weed & feed’ product in autumn as this is when those pesky little plants start growing. Just ensure that any selective herbicide product you use is safe for your lawn type especially if you have a buffalo lawn.
In between feedings pamper those all-important soil micro-organisms with regular applications of a hose-on seaweed based product as it’s these little soil workers that really help keep your lawn healthy.
4. Using it carelessly
Fertiliser is the easiest way to keep a lawn healthy, dense and green, but it can also create environmental concerns if not used responsibly.
Ensure you apply the right amount for your lawn size as more is not better it just means wastage.
As well as helping our environment by using less fertiliser, we can do even more by ensuring it stays where it’s intended. Take care when using it so it doesn’t get washed off your lawn into the street.
Never apply any type of fertiliser close to wetlands, rivers, streams, lakes and ponds. Heavy nutrient loads in these bodies of water will create excessive weed growth and algae blooms. Stay at least 2m away from water when applying fertiliser.
After fertilising, sweep up and collect what remains on hard surfaces, such as the driveway, or rain will wash it into water features, water ways and storm drains.
Using a quality slow release fertiliser helps to reduce the risks of nutrient run-off or leaching and healthy soil, one with lots of micro-organisms, is much better at retaining nutrients so keep those soil workers happy and healthy with regular applications of an organic seaweed based product. You can also rotate fertiliser applications to include an organic slow release fertiliser.
Dos and Dont’s
TEST the soil to learn its type before fertilising.
pH can matter when you are seeing problem spots.
USE any test results to choose the right fertiliser or other treatment.
Amend pH a few weeks before applying fertiliser and test again just before applying.
SPEND time accurately measuring the size of your lawn.
TRY an organic type of fertiliser and seaweed products to improve soil quality.
Only use quality, modern slow-release fertilisers.
BUY a quality fertiliser spreader that best fits your needs.
CALIBRATE the spreader to make sure you apply the right amount.
ENSURE that the spreader is well maintained.
KEEP records of what and how much you apply, and when.