When it comes to Houston soil drainage problems, we’ve just about got them all. Water is an essential soil ingredient for plant growth. However, too little or too much water will result in the decline or death of your garden plants.
Other than having the consistency of lake bottom “muck,” Houston soils stay wet for several reasons:
Compaction (foot traffic as well as the effects of the climate)
A limiting subsurface layer, like clay
High water table (even though the soil survey report for my city lot indicates the water table is “about 48 to 72 inches,” we dug a shallow hole and watched water drain into it from the sides of the hole)
When soils retain too much water, for whatever reason, roots suffocate, are susceptible to disease and will eventually die.
Symptoms of excess water include:
Yellowing of the leaves (chlorosis)
Defoliation (leaves drop off)
Marginal scorching (brown edges on leaves)
Any time plants are subject to stress, such as under-watering, as well as over-watering, mother nature calls in an army of “pests” to put the plants out of their misery. Healthy plants naturally repel non-beneficial insects as well as diseases.
Oxygen is another essential ingredient in healthy soils. Roots absorb oxygen from the soil and expel carbon dioxide back into the spaces between soil particles not filled with water. Without this normal exchange of O2 and CO2, plant roots die.
A good soil that drains well is 50% soil particles, 25% water and 25% oxygen. Within the air space in soil, you’ll find large pores and small pores. Under normal rainfall and irrigation, the small pores hold onto water while gravity pulls water down and out of the large pores and refills them with air. This maintains a good balance of air and water in the soil.
A soil percolation test is simple to perform and will tell you how well your soil drains.
Soil Percolation Test
- Dig a hole 18 o 24 inches deep; width is not important, but should be at least 6 inches wide for ease in taking measurements.
- Fill the hole with water all the way to the top and let the hole sit overnight.
- In the morning, refill the hole to within a couple of inches of the top.
- To aid in measurement, place a stick across the top of the hole and insert a second stick down into the water in the hole. Mark the water level on this stick and wait 30 minutes.
- Mark the water level after 30 minutes and again after 60 minutes.
- Measure the water level again the next day.
- Determine the average drop in water level per hour and refer to the table below to interpret your results.
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If the water level in your hole drops less than one half inch per hour, your soil drains poorly.
If the water level in your hole drops one half inch to one inch per hour, your soil drains moderately well.
If the water level in your hole drops more than one inch per hour, your soil drains well.