Planting Into 200 mm of Rain: Gel Strategy for Dryland Restoration Crews

Dryland restoration is a different discipline from landscaping. The planting window is short, the sites are far from water, and the crew that puts a seedling in the ground will not see it again for months. Gel is one of the few inputs that travels with the plant and keeps working after the truck leaves, which is why it has earned a permanent place in arid programmes. It only pays back when the dose and the depth are matched to the rainfall the site actually receives, not to the rainfall in the project proposal.

Start from the rainfall number, not the species list

Two sites twenty kilometres apart can differ by 150 mm a year, and that difference changes the dose more than the choice of species does. The bands below assume a planting hole of 2 to 3 litres, granulated polymer mixed through the backfill, and no irrigation after establishment.

Under 200 mm annual rainfall: 8 to 10 g per seedling
200 to 350 mm: 5 to 7 g per seedling
350 to 500 mm: 3 to 5 g per seedling
Deep-tube container stock on exposed sites: add 2 g to the figure above

Above 10 g in a 2 litre hole you are no longer buying survival. A 2 litre hole holds roughly 2 litres of soil. Ten grams of polymer at 300 times its weight is 3 litres of gel, more than the void it sits in. The pocket stays saturated, the root plug drowns in its own planting hole, and the first hot week finishes the job.

Depth, and the wick problem nobody warns you about

Place the gel 12 to 18 cm below the surface, mixed evenly through the backfill around the root plug, and leave the top 5 cm free of granules. There are two reasons.

The first is that granules near the surface intercept the small showers that would otherwise reach the root plug, then give that water back to the air within a day. A 6 mm shower is worth a great deal to a new seedling and worth nothing once it is held in the top 30 mm.

The second is stratification. In gravelly or cracking soils, a concentrated band of gel at one depth becomes a barrier rather than a reservoir. Water arrives, spreads sideways along the band, and never moves down to the roots below it. Mixing through 20 cm of backfill avoids the layer and gives roots something to grow into rather than something to sit on.

Plant into a hole at least twice the width of the tube and no deeper than the plug. Set the collar 1 to 2 cm below grade inside a shallow dish, so a 15 mm shower funnels toward the plant instead of running off the mound.

The planting window and the single follow-up watering

Plant with the season, not ahead of it. Seedlings put in three weeks before reliable rain sit in warm dry soil and lose condition before the gel has ever swelled, because dry granules compete with the root plug for the first water that arrives. The window opens when the subsoil at 20 cm is damp to the touch, not when the calendar says so.

At planting, give 3 to 5 litres per seedling, poured slowly in two passes so it soaks in rather than running off the dish. If the forecast holds, that is the only water the plant receives. If 21 days pass with less than 10 mm, a second 3 litres is worth the trip. A third is usually not: a seedling that has not rooted by week six will not be rescued by a schedule that arrives in week twelve.

Set a realistic target before the season starts. On harsh sites with good stock, correct depth and the doses above, 70 to 85 percent survival at twelve months is a reasonable expectation, and anything above 85 percent suggests the site was easier than the plan assumed. Measure it properly, in fixed transects, so next year’s dose is set by data rather than by habit.

For programmes buying by the tonne, fix the grade against the site before comparing prices: coarse granules for gravel and cracking clay, a potassium-based polyacrylate where the planting has to last three seasons, and absorption quoted in local water rather than distilled. The grade specifications give those figures side by side, which is what a tender document should be quoting.