March Hints

Fertilising turf.

If there’s one time of year when you get more benefit from fertilising your lawn than any other, it’s autumn. That’s because autumn is when Mother Nature works with you instead of against you. For example, days are getting shorter and nights cooler. Dews are heavier, and the pattern of rainfall starts to be more favourable to the needs of grass. As a result, grass plants start to increase their natural production of rhizomes. A single grass plant can send out many rhizomes, resulting in many new plants…all knit together to form thick green turf. Although the length of day and the weather trigger the growth process, how many rhizomes are produced (and therefore how thick the lawn will be) depends on the nutrients that are available to the grass roots. There is no reason why summer active lawns should deteriorate over winter months. The growth rate slows down, but with a controlled fertilising program lawns can stay green and healthy over most of winter.

The objective is to keep lawns active and this can be achieved by stimulating the grass. Start with a very light application in late summer, and a slightly heavier application in early autumn. Follow this with light applications every 5-6 weeks through winter.

The thicker and healthier the lawn is in winter, the better chance you have to control the annual weed problem. If fertilising this month, keep nitrogen and phosphorus applications to the minimum needed for the main summer-active turf grasses. This will reduce vigorous growth in annual weeds.

To intensify the green colour without increasing vigour, apply a soluble iron fertiliser such as sulphate of iron but be sure to water it in.

Couchgrass stops growing when temperatures fall below 15oC and will initiate dormancy when temperatures drop below 10oC for an extended period. Dormancy can last from a few weeks to several months depending on conditions. How you manage couch in autumn will determine its ability to tolerate cold-temperature stress and survive through winter.

In early autumn, as growth slows prior to the onset of dormancy, the plants convert soluble sugars to starch. They then store these starches in stolons, rhizomes and roots to serve as food reserves to ensure winter survival. Autumn management of any turfgrass should incorporate practices that increase food reserves and thereby increase stress tolerance.

Autumn fertiliser applications should be low in nitrogen and high in potassium. Try to use a fertiliser where the amount of potassium in the NPK analysis is equal to or greater than the amount of nitrogen.   Your local ALMA contractor can apply Potassium Nitrate which is the ideal autumn fertiliser.

Dry patches in turf are often caused by water repellence. The grains in sandy loams sometimes become water repellent by being coated with organic residues from some plant materials. Decomposition of the thatch produced by turf growth can produce hydrophobic materials that accumulate in the thatch and upper part of the root zone.

Testing for water repellence may be simply assessed by placing a drop of water on the dry soil and observing how long it takes for the drop to disappear.  Times under 8 seconds indicate no water repellence. Times over 4 minutes indicate severe repellence.

The best way of overcoming water repellence and dry patch is by the use of agricultural wetting agents. It has been found that three light applications, spread through the dry season, give better results than one large application early in the season.

Apply the wetting agent towards the end of the winter wet season (in September). Repeat applications should be made in November and March.

After each application, irrigate at a low rate, about 5-10mm per hour, so that the water can penetrate deeply into the affected area.

Dry spots in a lawn will be very evident by this time of the year. Before you race out and buy a beetle spray, look at some of the reasons why the dry patches may have developed.

The primary problem is thatching, that is the lawn grows above itself and the taller growth shades the lower leaves which die. The decaying vegetation creates a water repellent barrier between the surface and the root system, preventing water from penetrating the soil and the lawn dies of thirst.  Your local ALMA contractor can scarify your lawn to reduce the thatch build-up and produce a healthier lawn.

Most Native Plants will be in active growth over the rainy winter months. Like any other plants, natives need feeding and it makes sense to have the nutrients available just before their growth period. Fertilising plus mulching keeps them in good health. Alma No 4 fertiliser is low in Phosphorus and ideal for natives. Well composted horse, cow or pig manure or true blood and bone manure helps to condition the soil. Avoid poultry manure or manufactured organic fertilisers made from poultry manure because of the high phosphorus content. Coated slow release fertilisers or very low rates of lawn fertilisers are good. Do not use Complete D because it contains too much phosphorus.