Researching Maintenance

Old sprinklers Where do you obtain data on sprinklers that are older than 20 years or are no longer made?--California

I contacted several major sprinkler manufacturers and all of them told me they could supply specifications for old or discontinued sprinkler models. The companies archive this information, so it may require some time for retrieval, but it should be accessible. To obtain this information, simply call the company's customer-service number. They should also be able to tell you what, if any, available parts might still work with the older sprinklers.

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If for some reason you can't obtain manufacturer information (perhaps the company no longer exists), you easily can determine most aspects of performance on your own. Gallons per minute, coverage area and even a rough distribution curve are fairly easy to determine with simple tests you can perform yourself (see "Choosing a sprinkler: the ABCs of DRCs," in the June 1997 issue of Grounds Maintenance, for more information).

Synthetic oil Are synthetic oils better for small engines? How are they produced?--Nevada

Manufacturers create synthetic oils by reacting lightweight molecules together to form heavier molecules (oils) with the desired lubrication qualities. They blend several of these together for the final product. In contrast, conventional oils are simply refined from crude oil.

Anecdotes for and against synthetic oil abound, so the issue is not without some controversy. However, more or less general agreement exists on certain points.

First, synthetics perform well in cold conditions. In fact, it's one of the reasons they were first developed, and some engine manufacturers of both diesel and gasoline units specifically recommend synthetic oil in sub-zero temperatures. Although most grounds-care equipment is stored away during winter, snow blowers or generators might be good candidates for synthetic oil.

Synthetics also perform better in unusually hot conditions because they better resist heat-induced breakdown. In actuality, even average engine heat breaks down oil (but typically not before your next oil change is due). This is why synthetic oils last longer than conventional oils and why some synthetic-oil manufacturers recommend oil changes only every 20,000 or more miles in automobiles.

Finally, the claim that synthetic oil simply is a better lubricant-that it is "slipperier"-seems to have some merit. Engines with synthetic oil may run several degrees cooler due to slightly less friction and reportedly get better fuel economy.

As you can see, synthetic oils offer definite advantages. So why doesn't everyone use synthetic oil? One of the reasons is that you don't change oil only for the sake of getting fresh oil back into the engine. You also remove the contamination that has accumulated in the oil and filter. True, some of the contaminants are oil-breakdown products of which you get less with synthetics, but not all. Therefore, mechanics suggest that, even if you do use synthetics to extend the time between oil changes, you should still change your filter as often as you always have (or at least more often than you change the oil).

However, that is a strategy best reserved for on-road vehicles. Grounds equipment often operates in much more dirty or dusty conditions. In such situations, you're wise to change the oil and filter often to eliminate environmental contaminants. Thus, the lifespan of the oil may be less of an issue than with automobiles.

This brings up an important point: You may be voiding your engine's warranty if you don't follow recommended maintenance intervals. Therefore, it's best to stick with manufacturer recommendations regardless of the oil you use.

Even if synthetic oil is a better overall lubricant, some (but definitely not all) mechanics feel that, in normal operating conditions, you can gainas much benefit by simply changing conventional oil more often. Increasing oil-c hange frequency still might not cost as much as switching to synthetic oil, which is two to four times more expensive than conventional products.

Finally, if you have an older engine that leaks or burns oil, it will leak or burn even more oil if you use a synthetic. In this case, it's better to stick to conventional oil.

What is "compost"? Is leaf compost a topsoil or should it be used as an amendment?--Connecticut

Terminology can be confusing in cases like this. "Topsoil" and "compost" refer to materials, whereas "mulch" and "amendment" refer to the use of the material. Leaf compost is not "topsoil," a much-misused term that refers to the humus-rich, dark-colored surface layer of a natural soil profile. If, by "topsoil," you're implying "mulch," then the answer to your question is no, leaf compost is not typically used as mulch. "Mulch" refers to any substance applied on top of the soil surface to conserve water, suppress weeds and provide decorative value. Such material can consist of anything from plastic or fabric, to wood or bark chips, leaves, grass clippings, rocks or even shredded paper. Mulch should stay put (that is, resist washing out or blowing around), it should not decompose quickly and it should be able to suppress weed growth.

Compost, then, does not have the qualities that would make it a good mulch. However, it does (if it's been composted properly) have qualities that make it an excellent soil amendment, such as being reasonably free of weeds and pathogens, rich in nutrients and possessing good physical qualities such as moisture retention and good aeration and tilth.

Arborists frequently tout the benefits of mulching around trees, and rightly so. They point out that mulch reduces soil compaction, suppresses weed growth, conserves moisture and--by eliminating the need to mow and trim around trunks--stops equipment damage. Unfortunately, some maintenance contractors apply excessive--sometimes enormous--amounts of mulch around trunks, and the practice seems to be getting more common.

Chris Carlson, a horticulturist at Kent State University (Salem, Ohio), recently compiled a list of the possible negative consequences of over-mulching. Among them: * Oxygen starvation of shallow roots leads to decline of the root system * Phloem death (due to lack of oxygen exchange) occurs in the buried portions of the trunk * The risk of fungal and bacterial infections increases due to constant moisture around the trunk * Excessive heat from decomposition of the mulch can directly kill stem and trunk tissue * Depending on the material, mulch can make the underlying soil's pH extremely acidic (such as with pine needles) or extremely alkaline (as with some hardwood bark), which can lead to nutritional problems * Deep mulch provides hiding places for rodents that can chew extensive swaths of bark from the trunk, even completely girdling trees * Microbes present in the decomposing mulch can compete with the tree's roots for nitrogen.

Carlson provides a few guidelines for preventing problems with mulch. First, and most obviously, keep mulch layers thin. No more than 2 inches if soil is not well drained; up to 4 inches if drainage is good. More finely textured mulches should be no thicker than 1 or 2 inches. This is because fine-textured material allows less oxygen penetration than coarser materials (such as nuggets). If a site is very poorly drained, avoid mulch altogether and use herbicides for weed control.

If a client wants a finished, "fresh" look, simply rake the surface. Mulch dyes also are available to create a newer, more tended look.

As a general rule, Carlson suggests keeping mulch 3 to 5 inches away from trunks of young trees and 8 to 12 inches from trunks of older specimens. If you "inherit" a heavily mulched tree, inspect the mulch's depth. If the root collar (the junction between the stem and the roots) is buried, excavate around the tree until the collar is exposed. This will allow the collar to dry out and can rapidly improve vigor and appearance of trees suffering due to mulch-related problems.

Thatch accumulation is the natural result of intensive management of certain turfgrasses. Golf greens are probably the most intensively managed turf sites in existence, so it's not surprising that superintendents must constantly address thatch problems. However, opinions vary about how to best reduce thatch in bentgrass greens. To clarify the effects of various practices, University of Tennessee researchers examined the effects of several mechanical and chemical treatments.

The researchers included vertical mowing, topdressing and core aerating as well as applications of lime, supplemental potassium (K) and a wetting agent, individually and in various combinations. These are all practices superintendents perform to reduce thatch, or at least for which claims of thatch reduction have been made. The treatments were applied for 6 years, and the data was analyzed for the last 3 years of the study, during which the investigators measured resulting thatch levels.

The researchers found that supplemental K (in addition to the 6-12-12 maintenance nutrition supplied to all plots, including the control) actually increased thatch thickness. The same was true of the wetting agent, which may have sped drying of the thatch layer, reducing decomposition.

Other studies have suggested that calcium may aid thatch decomposition, but the lime (CaCO3) treatments in this study did not affect thatch depth. However, the lime did increase pH significantly, which could have counteracted any benefit from the calcium (thatch decomposition occurs most readily within a certain pH range).

So which treatments worked? The tried-and-true methods: mechanical treatments--vertical mowing and core aerating--and topdressing. These practices, especially in combination, provided the greatest reduction in thatch. Topdressing (6 times a year) combined with vertical mowing (4 or 8 times a year) or with vertical mowing and core aerating (both 4 times a year) provided the greatest benefits. Topdressing by itself reduced thatch compared to non-topdressed plots, but not as much as the combined treatments.

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