Successful lawn maintenance involves a number of cultural practices that are used throughout the growing season. Proper implementation of mowing, irrigation, thatch, weed, insect and disease control, and fertility can prevent a lot of the problems experienced in home lawn care to produce a dense, healthy, high quality turf that requires less water.
The importance of good mowing practices is often overlooked but has a major influence on turf density, uniformity and aesthetic quality of a home lawn. It is the most repetitious and time-consuming maintenance practice, but is also the most abused.
The frequency and height of cut are two important considerations and will vary depending on species of grass and growing conditions. Turf grasses can be mowed frequently, provided that no more than one-third of the grass blade is removed in a single mowing. Bluegrass and fine leafed fescue should not be cut lower than 4-6 cm. Cutting shorter than this means the grass plant has to use carbohydrates from the root reserves to initiate new growth. Repeated scalping of the turf weakens the root system, directly affecting the ability of the turf to obtain water and nutrients. Lower mowing produces a shallow root system, making the grasses more succulent and susceptible to heat and drought stress and disease injury.
A higher height of cut gives a better safety margin, because the grass is hardier, more drought resistant, less disease susceptible, requires less water and remains green longer than at a lower height of cut. Grass clippings are not normally removed from a home lawn unless they are excessively heavy. Clippings have a high nutrient value, breakdown rapidly and do not contribute significantly to thatch. If clippings are removed on a regular basis, then fertilizer, particularly nitrogen, have to be increased by 20 to 35 % to compensate for their removal. It may be desirable to remove clippings in some instances, such as around pool areas, but in most cases, clippings can be returned without causing any problems.
Lawns mow better when dry than wet. Dry grass cuts more cleanly and clippings tend to distribute much more evenly.
Mowing equipment should have the capacity and power to handle the area to be mowed. Other considerations in equipment selection should be weight, maneuverability, ease in starting, ease of adjustment of height of cut and safety features providing protection from mower blades. Reel type mowers provide a better cutting action than rotary mowers, but are seldom used on home lawns because of their high initial cost and maintenance requirements, and also because they are more difficult to use than rotary mowers. A rotary mower will provide adequate mowing if the cutting blade is kept sharp; otherwise, it tears or shreds grass blades, producing a dull, gray-brown overcast appearance that can be misinterpreted as symptoms of other turf problems. Grasses with shredded leaf tips are also more easily infected by disease organisms. Debris such as sticks, stones, wire, etc. should be removed before mowing to prevent possible injury.
Thatch is a layer of partially decomposed organic matter that builds up in between the lawn and soil surface. It is a common problem on home lawns, particularly for lawns that have been established for several years.
An excessive thatch layer, as shown in Figure 1, can restrict grass roots penetration into the soil root zone, resulting in a lawn with shallow root systems. Thatch can also interfere with water infiltration as it repels water, therefore increasing the potential for damage during dry periods.
Thatch provides a perfect winter survival and growing environment for insects and diseases. If thatch is kept to a minimum, then insect and disease-related problems are also reduced. When a thatch layer is present, the lawn feels very spongy upon walking. By cutting a triangular patch of turf with a sharp knife and lifting it back, the thickness of the thatch layer can be measured. More than 2.5 cm of thatch indicates that steps should be undertaken to reduce this layer.
Cultural practices such as frequent mowing, avoiding over-watering and preventing over-fertilization can minimize thatch development. If excess thatch is present, mechanical removal by vertical mowing using a dethatcher should be done gradually. Another method of controlling thatch is aerating or coring. The hollow steel tine core aerator removes cores of soil which physically breaks up the thatch as well as bringing up beneficial soil microorganisms that help break down the thatch. Dethatching or aeration is recommended in spring and fall during periods of good growth, allowing for quick lawn recovery.
Figure 1: Excessive thatch layer
A thick vigorous lawn is the best prevention against weed invasion. A dense stand of turf can compete successfully with weed seedlings for light and nutrients.
Potential weed invasion may occur when there are thin or damaged areas in the turf. Areas exposed to heavy foot traffic are usually sites of weed invasion, as many weeds require light to germinate and can thrive in compact soil conditions more successfully than most turf species.
Problem weeds include both broad-leaved and grass weeds that can be controlled by a number of methods including hand pulling, hand raking, mowing to prevent seed formation, and application of selective herbicides. A combination of methods may be the best way to control most weeds.
Before attempting any weed control, weeds should be properly identified.
Insects that infest home lawns are generally difficult to notice and their presence goes undetected until significant damage has been done.
Symptoms associated with drought stress can sometimes be caused by insects. If the lawn remains brown or show signs of thinning out despite watering, then closer examination for insects should be done. Inspection of the leaves, stems, roots, thatch and soil will help to determine if the problem is insect-related.
If good management practices are used, disease problems in home lawns are minimal. Excessive use of fertilizers can cause succulent growth that is more susceptible to diseases. When establishing or renovating a lawn area, select varieties that are resistant to various diseases. If the lawn has a history of disease, it may be advisable to apply several preventative sprays to avoid damage.
Understanding and implementing a well balanced fertilizer program is one of the most important factors in maintaining an attractive healthy lawn. Factors that will determine the most suitable fertilizer regime for an individual home lawn are soil type, climate, irrigation, mowing practices and species of grass.
The three main nutrients required by turfgrass are nitrogen, phosphorus and potassium. Nitrogen promotes dark green color, leaf and blade development and density of the turf. Phosphorus is important for good root and rhizome development and promoting plant maturity. Potassium contributes to the general vigor of the plant and promotes wear and drought tolerance and hardiness against winter injury.
The amount of nutrients required by a home lawn is most accurately determined by soil testing. A soil test will provide levels of phosphorus, potassium, pH and lime requirements. Nitrogen has to be replenished every year, while phosphorus and potassium are relatively stable in the soil. On newly established lawns, higher levels of phosphorus and potash may be required. If the lawn is on sandy soil, higher potash or more frequent applications may be required as it may be subject to leaching under these conditions.
Various forms of nitrogen are used in lawn fertilizers for homeowners. Water soluble or inorganic nitrogen fertilizers such as ammonium nitrate and ammonium sulfate supply a form of nitrogen that is immediately available to the plant. The response of turf is a quick greening. However, this form of nitrogen is readily leachable and can cause lush growth if applied in hot or dry conditions. It also has high potential to burn the turf.
Natural organic fertilizers such as activated sewage sludge rely on soil microorganisms to break down the organic compounds into a nitrogen form that can be taken up by the grass roots. These forms of fertilizers depend on soil temperature to release nitrogen and the rate of release may vary with the product. Although urea is sometimes referred to as an organic form of nitrogen, it reacts similarly to water soluble carriers in the soil and is therefore referred to as a water soluble nitrogen form.
Synthetic organic forms of nitrogen such as IBDU, ureaformaldehyde and sulfur coated ureas provide slow release properties that reduce nitrogen leaching and have lower potential for burning turf due to a low salt index. These forms are generally more expensive than the water soluble or organic forms of nitrogen. However, their slow release characteristics coincide with soil temperature and moisture conducive to good turf growth.
Fall fertilization with slow release nitrogen fertilizers has proven to be beneficial to home lawns. Late fall fertilization when the vertical shoot growth has ceased increases fall and spring root growth and encourages active tillering, therefore promoting a thicker stand. The lawn comes out of the winter in a green condition and does not give the rapid flush of shoot growth that occurs with spring-applied nitrogen.
Application of lawn fertilizers is very important in achieving uniform results. If using a drop type spreader, operate it the long way of the lawn. First apply header strips at each end of the lawn to provide room for turning. Overlap one wheel's width when spreading the fertilizer and shut off the spreader when reaching the header strips. With a centrifugal type spreader, make two split (half rate each) applications at right angle to each other. Always make sure that the spreader is properly adjusted, otherwise you could end up with striping or uneven color that would detract from the overall appearance of the lawn.
Ontario Ministry of Agriculture, Food, and Rural Affairs, www.gov.on.ca (permission pending)