Does The Soil Drain Well?
Most landscape plants come with the advice to put them is a soil that drains well. Drainage is important to the long term health of your plants.
The health of plants in the yard depends on the soil's ability to quickly drain away excess water from the its surface. If water fills all the pores in the soil and hangs around for days and weeks, there is no room for oxygen and the plants drown. There are very few, although there are some, plants that tolerate such boggy soil conditions.
Normal, healthy soil manages to simultaneously drain well, yet retain moisture for use by the plants later. It is able to do this only because its structure is loose--not compacted--and, because of its physical and chemical composition.
Observe Puddles After A Rain - While puddles may indicate compacted soil, they also indicate drainage problems. Even compressed soil, if has certain physical and chemical properties will drain halfway decently. So the puddles may be signaling deficiencies in the composition of your soil.
Check Water Run-off - Like puddles, rivulets of water that run off the turf when it rains rather than soak into the soil, are suspicious. Water flowing off the lawn in streams similar to the flow of run-off down the driveway when it rains suggest that soil under your grass may be just as incapable of absorbing water as the paved drive! Obviously, this soil needs repair if it is to support healthy landscape plants.
Hole Test - To be sure, use this drainage test. Dig a hole in the yard about the size of a gallon jug. Fill that hole with water and let it drain. As soon as the water has completely drained, immediately fill it again and keep track of how much time it takes to drain. If it takes more than 8 hours to drain, you have a drainage problem that needs attention. Serious drainage problems generally require a professional contractor’s services.
Evaluate Water Penetration
Examine a sample core of your turf after a good rain or after you’ve applied an inch of water to the lawn. If your soil's drainage is satisfactory, the core should be moist all the way through its 4 to 6 inch depth.
Another way to determine just how deeply an inch of rain has penetrated the soil is to use a houseplant water meter. Take it outside and insert the probe into the turf as you would into a container holding a plant. Do this at several spots over the lawn area. The meter will register the degree of moisture at each site. Where soil is dry, compaction may be the culprit.
Test Water Retention
While good drainage is essential, so is a soil's ability to hold water. This sounds like a contradiction, but it is not really. A sandy soil has excellent drainage, but is lacks the capacity to hold water long enough to make it available to plants. Good soil has both traits. As with compaction and drainage problems, adding organic matter can correct the situation. The loam acts as a sponge, absorbing water to serve plant roots.
There is no simple test to determine your soils water retention characteristics, but there is a good guideline—how often you need to water your garden or lawn. A healthy soil has a lot of sponge-like material in it that holds water until the roots of the plants need to use that water. If soil is not compacted, that water can be stored down many feet below the surface of the soil. If your garden, shrubs, or lawn need watering every 2 or 3 days, you have a water retention problem. It might be because the soil is compacted and the roots are only two inches deep. It might be because you soil is very sandy and needs more sponge-like material. A healthy lawn in the summer-time should not need to be watered much more than once a week to ten days if there has been no rain. The same goes for the vegetable or flower garden as long as it is well mulched.