Simply put, well-drained soil is soil that allows water to run off at a moderate rate, without stagnation or puddles. “Well-draining soil” is soil that contains enough pores, spaces between soil particles, to allow air and water to flow freely.
Well-drained soils allow water to move through them easily. Well-drained soil fails to retain water, and it also struggles to absorb it. As a rule, well-compacted soil is synonymous with poorly-drained soil. Many plant species grow well in drained soil because water would otherwise drown their roots.
Well-drained soil has a loose structure that allows water and air to move quickly through the soil particles because, along with moisture, plant roots need a lot of oxygen to survive.
Excess water due to soil drainage problems can limit the amount of oxygen reaching plant roots. When the soil does not drain quickly enough and the plants remain in the collection water, their uptake of oxygen from the soil is reduced and the plants may die. The roots of your plants need oxygen just like they need water, but if they are in damp soil their oxygen uptake from the soil is reduced and they may suffer from root rot, they are more susceptible to disease and damage, insects and may eventually finally die.
The Growth of Roots in Soil
The roots can still get the water they need, but the water doesn’t stay in the soil long enough to cause problems like root rot. Too much water and not enough air is a common cause of root rot and many other problems. In heavy clay, you may have the opposite problem, where the water takes a long time to drain, causing root rot due to lack of air. If you have too much air in your soil, it will deplete quickly and your plants won’t have enough time to absorb water.
Well-drained soil is very important for most plants because it means the plants won’t be stuck in the pool and the soil will have enough time to absorb the water. Well-drained soil will ensure that the plant’s roots do not submerge in water and allow air and oxygen to reach the roots. Well-drained soil can hold water long enough for the roots to take up the water the plants need, and dry long enough between rains or waterings so the roots can absorb oxygen without rotting from too much water.
When soil drains well, it means that the soil retains water, but the water in the soil does not consistently exceed its intake.
Gravity pulls water out of the pores, deep into the soil, and ultimately away from where the plant’s roots are—mostly around the tops of the feet—and down deeper, eventually draining into surrounding streams, rivers, lakes, and oceans .Once these channels – pores – on Earth are filled with water, the old gravity comes into play. When you aerate the soil, you create more space between soil particles so water can move more easily. A good soil mixture drains well and the spaces between soil particles are evenly distributed between water and air.
How Water Retention Is Improved
To improve water retention in sandy soil or drainage in clay, it is often easier to simply cover with a layer of good quality garden soil (about 20 cm is sufficient). For example, for succulents and cacti that don’t need much water, sandy soils that drain well and dry quickly are preferred. If you have rough, sandy soil, you may notice that water drains quickly through the rough soil, so your plants dry out and wilt more quickly.
On the other hand, if you have really sandy soil and a lower water table, water can run out of the root zone so quickly that our houseplants lose the benefit of water entirely. Unless your garden is flat or along water, if you have sandy or loamy soil, your natural drainage is almost certainly good. If your garden is located in an area that is prone to floods or heavy rains in the spring or summer, there are some steps you need to take to improve soil drainage.
If you have an area in your yard where the soil stays wet for a long time, it’s best to just choose plants that do well in poorly drained, damp soil.
In poorly drained soils, most of the pore space is filled with water for a long time and there is too little air. Poorly drained soils can also cause runoff, where soil and nutrients are lost when washed away by rain or irrigation.
The Effects of Soil Compaction
When soil is compacted, it prevents water from flowing freely through the soil, resulting in poor drainage. Even good soil that has been compacted by heavy machinery or constant foot traffic also has no space between the particles for water to flow. The spaces between the solid particles of any soil are filled with oxygen and water, which are essential for healthy plant growth.
Soils with good porosity throughout the rooting depth allow substantial amounts of water to pass through the soil profile without affecting plant roots unless the site has a naturally high water table. Although soil replacement is difficult, you can replace the site to minimize poor physical drainage.
It is curious that when the clay soil dries out over time, which usually happens only during a drought, cracks, hardens and even repels water, then the poor plants growing there pass through the soil so dense and moist that their roots can hardly breathe at such a temperature. so dry water is difficult to penetrate. Difficult, clay soils can crack at the surface when dry, creating cracks that expose roots to sun and dry heat. As the clay dries, it uses reverse osmosis to extract water from plant roots to maintain moisture levels.
Yes, plants need water of course, but the roots that bring water to plants need something else: oxygen. If there is too much air, there is not enough water for photosynthesis and nutrient transport. You can improve soil drainage by adding organic materials such as compost or aged manure.