The grass may be greener, but the lawn could be in trouble

When many people set about greening their lawns in the spring, they might just as well be redecorating a structurally flawed house that could collapse at any moment. That, anyway, is the problem lawn care specialists have seen emerging over the past several years; and they blame the exclusive use of weed killers and artificial fertilizers.

Lawns treated this way are ``structurally flawed'' because these methods have led to compacted soil and the now-common problem of thatch -- a dense mat of living and dead root tissue on the soil surface. Once these twin conditions become established, the lawn becomes vulnerable to more-obvious surface-marring conditions. The thatch sheds rather than absorbs water and leads to soil compaction, which further resists water penetration.

The response of recently established lawns (particularly those on soils rich in humus) to artificial fertilizing can be dramatic. Lawns will green up within a matter of days even in cool spring weather. But these highly soluble nutrients do their work at the expense of deep, penetrating roots. Consequently the lawn is more vulnerable to drought.

The answer is to strike a balance: to adopt a system that boosts soil quality so that it can absorb moisture and promote the deep rooting that is a feature of all healthy lawns.

To this end, recent findings at Michigan State University are most encouraging. When leading turf specialists there began evaluating a new biologically enriched organic lawn fertilizer -- a blend of natural ingredients that also includes soil bacteria and enzymes -- some unexpected results were forthcoming.

The product was found to promote a healthy, green turf and to steadily do away with thatch build-up (the principle aim behind its formulation). But in addition -- and this was totally unexpected -- the fertilizer also reduced and eventually eliminated other associated lawn problems such as dollar spot, fusarium, yellow patch, and the like.

Further testing confirmed the initial observations. These lawn problems were not so much destroyed as overwhelmed. By introducing beneficial bacteria along with slow-release natural plant foods into the lawn, the hostile microorganisms were no longer a dominating presence. In simple terms, once a more natural, balanced situation was established, the turf problems disappeared.

Improving the soil while greening up the lawn doesn't automatically mean abandoning the use of all chemicals for either feeding or judicious weed control. But soil quality must be adequately maintained by including natural fertilizers in the maintenance schedule.

Fully half of all lawns exclusively fed artificial fertilizers develop thatch within three to five years. Today special lawnmower attachments are available that will mechanically rip up that thatch. But the point remains, thatch is a man-made condition, not a natural one, and need never occur.

Lawns with heavy thatch or with other entrenched problems will not necessarily respond simply to the application of a basic organic fertilizer. The soil life is often too far out of kilter for that. The need in these situations is for biologically enriched lawn foods -- those containing microorganisms and enzymes as well as plant foods -- so that a balance can quickly be restored. Another option is to try spreading a quarter inch of rich garden soil that has not been heavily treated with chemicals in recent years over the surface of the lawn.

Sources for bio-lawn fertilizers include: Ringer Research, Eden Prairie, Minn. 55344 (makers of the products tested at Michigan State); and Natural Gardening Research Center, Box 149, Sunman, Ind. 47041.