Gardening on Silty Soil

I think you should consider yourself lucky if you’re growing or gardening with silty soil. Next to loamy soil silty soil tends to be fertile. The irregular shape and small size of its soil particles (between 0.002 and 0.02mm) allows for good aeration. At the same time, it can hold on to water like clay soil but drains better than sandy soil.

Silty soil is often found in river valleys, so if your garden is sitting beside a river or was once a riverbed, the chances are you may be working with this soil type.

Improving Silty Soil

Hang on if you say silty soils are so good and naturally fertile, why would you need to improve it?

That is because the strength is also its greatest weakness. The ground is prone to compaction and this can cause the soil to become waterlogged and this retention of water results in poor air circulatation, choking the roots and preventing them from absorbing much needed nutrients, similar to a clay soil.

The first aid to compacted soil is good soil structure—good aeration, better water drainage, and dynamic soil biology for beneficial microbes such as mycorrhizae to thrive.

The question then is how do you improve a silty soil? Two main ways:

1. Add organic matter.

Yearly, amend silty soil with a good layer (3cm or 1 inch) of organic matter like compost, thoroughly decayed sawdust, or wood shavings. Add organic fertilisers when needed and cover the soil with 5 to 10 cm (2 to 3 inches) of mulch. The compost will encourage beneficial soil biology to thrive for healthier, hardier plants; the organic fertiliser will act as plant food; and the mulch will protect the plants from drought, erosion and weeds.

Make sure you turn over several inches of the top layer of the soil every so often to keep the soil crumbly and easily manipulated.

2. Avoid compaction.

Because silt is almost as fine as clay, its soil particles could get densely and tightly packed if mishandled.

Minimise walking on garden beds to prevent compacting the soil. One trick is to use narrow boards as pathways between plots or beds, especially in vegetable gardens, where you can walk or stay on when taking care of your garden.

You can also consider planting on raised beds so you won’t need to step on the soil at all.

Some gardeners amend silty soil by adding clay or sand but this won’t help much in improving it and perhaps is a practise that should be avoided. 

Watering Silty Soil

Silty soil has numerous tiny air spaces where water can pool and as such it is better at water retention than sandy soil. However since it is good at holding on to water, like clay soil, silty soil tends to become waterlogged. To prevent this, avoid overwatering your beds and plots.

The effect of overwatering is you clog up the air pockets, and the lack of breathing space chokes the roots the effect is the roots rot (appear as brown, black, grey, or slimy). The consequence of this is the nutrients needed by the plants to survive are not available and the plants die. The symptoms of overwatering are your plants have light green to yellow leaves and the foliage is wilted despite the fact that you’ve been watering regularly. Whereas if underwatering is spotted in time it is usually possible to save the plant the same is not true of overwatering.

Just as with clay soil, working silty soil while it’s too wet can damage it and it can take a very long while to recover.

Overwatering is usually due to repeated watering but if you’re too wary of drowning your plants, there’s a chance that you might be watering too lightly as well. When plants don’t get enough water, the roots don’t burrow deep enough into the soil so they become prone to drought stress and are usually competing with weeds for nutrients.

How do you know when it’s the right time to water? When you pinch the topsoil, it’s dry to the touch. Lastly, make sure that you give the soil time to dry in between watering sessions. This will allow the roots to dig deeper into the soil, avoiding shallow rooting.