Infiltration of irrigation water

Choosing the right irrigation design is critical for achieving optimal irrigation scheduling.

You might have the most sophisticated tools and technology, but if your irrigation system does not place water where it is needed – or fails to account for how water infiltrates into the soil and where roots develop – your irrigation scheduling will fall short. These considerations are also vital when determining where to monitor soil moisture.

While many factors come into play, I will use the following three pictures as examples to highlight common issues and provide practical solutions (without redesigning the infrastructure):
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1. Micro sprinklers hanging too high (+- 70cm).

– The higher a sprinkler hangs above the ground, the wider its wetted width, and the greater the evaporation losses (especially on hot, windy days).
– If water is placed in the tractor row, where there are minimal tree feeder roots, the soil will saturate quickly leading to surface run off. As a result, the grower stops irrigating.
– In reality, there is poor water infiltration in the active root zone, and the subsoil dries out, resulting in plant stress.
– This issue is aggravated on heavier ridged soils.
– The depicted farm has limited water supplies and it is wasting water due to evaporative losses, runoff and water being placed in the working rows.
Recommendation : Extend hanging pipes so that the spitters are about 30cm above the ground. Ensure the correct spreader is used to avoid water in the tractor rows.
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2. Micro sprinkler placed in line with tree trunks on a terrace.
(image shows the correct placement).

– On steep terrain, terraces are often built, and the “drop-off” typically starts just beyond the tree’s stem.
– If a sprinkler is placed in line with the trunks (as is common practice), half the water is applied on the slope of the terrace, where it runs off into the tractor row – resulting in poor infiltration in the root zone.
– As with the previous example, water is wasted and the plant suffers from water stress due to a dry subsoil.
Recommendation : Move sprinkler to a position halfway between the tractor wheel track and tree trunks. Use a narrow-range spreader to focus on wetting the active root zone.
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3. High delivery micro sprinkler and compacted soil with poor water infiltration.

– A narrow range spreader has been used, delivering water at a rate that exceeds the infiltration rate of the compacted soil.
– The soil in the ridge is compacted and has a low infiltration rate.
– The result, water infiltrates poorly on the ridge, runs into the tractor row and accumulates,  while the ridge and subsoil remain dry, resulting in plant stress.
Recommendation : Test the soil chemistry, consider applying a soil conditioning product to improve infiltration, use mulching and consider decreasing the emitter delivery.

When in doubt, dig a hole. Or contact MuddyBoots.