August 30, 2008

Fertilize Cool-Season Grasses in September

The best time to fertilize cool season lawns grasses, like tall fescue and Kentucky bluegrass, is in September, as they respond to shorter days and cooler temperatures with renewed growth.

Use a turfgrass fertilizer that is high in nitrogen, which appears as the first number in the three-number sequence called the fertilizer analysis that appears on the bag.

Distribute fertilizer according to directions on the bag; either a gravity flow (drop) spreader or a rotary/cyclone type can be used.

Remember that you must overlap each pass made with a drop spreader to compensate for the wheels; otherwise, conspicuous skips will result. The distribution pattern from a rotary spreader should overlap slightly with each pass because the pattern feathers out at the edge.

Spreaders may not distribute the same amount of fertilizer over an area, even if they are the same model, set at the same opening. The walking speed of the operator can also influence the distribution rate of some spreaders.

Rather than going through a complicated calibration process to adjust a spreader properly, some people simply put the required amount of fertilizer to cover a known area into the hopper, then adjust the spreader opening to a very low setting, then go back and forth over the measured area until the fertilizer runs out.

Using a low setting, combined with several trips across the lawn helps to ensure uniform application at the proper rate.

If fertilizer gets into the street, be sure to sweep it up before it gets into a storm drain where it could contaminate surface water downstream.

To receive a publication about fertilizing lawns in Kansas, call the Shawnee County Extension Master Gardener Response-Line at 357- GROW weekday afternoons.

Core aeration -- Fall is an excellent time to perform cultivation procedures that benefit established cool season lawns like Kentucky bluegrass and tall fescue.

Core aerators are used to improve the rooting environment of an existing stand of grass. These implements have hollow or open tines that pull out cores of soil.

This opens up channels into the soil improving the infiltration of air, water, fertilizer and pesticides.

Leave the soil cores on the soil surface after aeration. They will gradually break down, and as they melt back into the turf, they inoculate the thatch layer with micro-organisms that help to decompose thatch.

Note: So-called aerators, that consist of solid tines that simply poke holes into the ground, should be avoided for aerating home lawns because they create lateral compaction in the process.

September is an excellent time to core aerate cool season lawns. Aeration holes should be about 3 inches deep and no more than 3 inches apart. This may require several passes over the area with the aerator.

Adequate soil moisture is necessary for successful core aeration. It should be moist enough to permit penetration into the soil, but not so wet that the cores plug up the open tines.

Core aerators are available at equipment rental outlets, garden centers and some hardware stores.

Controlling broadleaved weeds -- Fall is the best time to control broadleaved weeds such as dandelions, plantain and bindweed in home lawns.

In the fall, the metabolism of the weed is downward -- food reserves are being accumulated in roots and crowns. Systemic herbicides are readily translocated throughout the plant during this time. And, sensitive garden and landscape plants are less susceptible to off target herbicide damage.

Scattered weeds can be spot sprayed using a canister type pump- up compressed air sprayer. Where weeds are more generally distributed throughout a lawn, a broadcast hose-end type sprayer can be used.

Granular herbicides can also be applied. These products are available individually or in combination with fertilizer as "weed and feed" materials.

For effective control of broadleaved weeds with herbicides, the weeds you want to kill should be in an active stage of growth and should have a lot of exposed leaf surface.

Skip a mowing or two before applying a herbicide, and don't mow immediately after making a herbicide treatment.

Granular herbicides for broadleaf weed control must be applied when the foliage of the target weeds is wet so the herbicide particles will stick to the leaves (pre-moistening may be required).

If winter annual weeds like chickweed and henbit have been a recurring problem, wait to treat until small seedlings of these species are present, usually in late October to early November.

Remember that an application of herbicide can interfere with successful seeding or overseeding. Make sure you understand the waiting interval that applies to herbicide application before and after planting grass seed.

Phil Sell is a retired agent emeritus with K-State Research and Extension.

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