Critical Area Planting

Bare ground does not stay put: rain lands with nothing to break its fall, crusts the surface and runs off carrying soil. Critical area planting gets living cover back on ground cut, filled, scoured or stripped bare - a new swale berm, a dam face, a track scar - before the first heavy rain. Cover need not be complete: full cover all but ends runoff and erosion, and even three tenths cuts erosion by about seventy percent. The figures come from ordinary farmland; this practice treats worse, so read them as the direction of the gain.

What decides whether seed takes is contact with soil. Sowing too deep, or onto loose cloddy ground, is the commonest reason a planting fails; most small seed wants 6 to 13 mm (a quarter to half an inch) of cover on a fine firm bed. Soil temperature governs timing, not the calendar: cool-season plants germinate best at 7 to 13 degrees C (45 to 55 F), warm-season ones at 13 to 18 degrees C (55 to 65 F). Sow early and disease takes the seedlings; sow late and they meet drought and weeds at once. On degraded ground lime and fertiliser want six to twenty-four months of lead time, which rarely fits ground disturbed last week.

The characteristic failure is the gap: a sowing protects nothing until it has come up and knitted, so a storm then takes seed and soil together. Mulch covers that gap and is part of the work, not a finish. On slopes too steep to hold anchored mulch, a biodegradable blanket keyed into a shallow trench along the top does the same and rots into the stand. Weeds and early grazing also cause failure, so stock and traffic stay off until the stand closes. Look two weeks after sowing and patch thin places at once: a sparse patch becomes a rill, then a gully. No planting holds a slope steeper than the soil will stand at, or a bank undercut by running water. After a season or two of watching and patching, the stand looks after itself.