Soil salinity is not a commonly discussed topic when it comes to vegetable gardening but it is something that we should be aware of as gardeners.
Soils naturally contain salts in them but the amount of salt contained in the soil is different at each location and can change over time. Arid, semi-arid and coastal areas naturally contain saline soils, while changes in the weather can also naturally affect the amount of salt in the soil.
Soils can also become salinized as a result of human actions including adding excessive chemical fertilizer applications and changes in sea level due to climate change.
Vegetable plants are negatively affected by high levels of soil salinity. Plants affected by soil salinity show signs of water stress and nutrient deficiencies. This is because a high amount of salt in the soil reduces the amount of water and the amount of essential nutrients, such as nitrogen, potassium and calcium, that plants can take-up.
Due to the large negative impact that high soil salinity can have on your vegetable garden, it is important that you use techniques that prevent the soil in your garden from becoming too saline. This is especially important if you are gardening in a coastal, arid or semi-arid area and during drought times.
- Ensure that your garden soil has enough drainage
Salts can easily accumulate in soil that doesn’t have enough drainage. Water from most sources naturally has a certain amount of dissolved salts. If the water used to water your vegetable garden isn’t allowed to flow out of the soil due to poor drainage, the salts dissolved in the water will make your garden soil even more saline.
On the other hand, proper drainage will make the soil less saline over time. Salts in the soil can dissolve in water that is added to the soil. If this water with dissolved salts can easily flow out of the soil, it will carry away salts from the soil, making the soil less saline.
- Water your garden using water with low levels of salts
If you live in a coastal area or other area in which the groundwater has a high-level of salts, you should not use well water to water your vegetable garden. Instead, you can use tap water/mainline water for your vegetable garden, as mainline water usually has low levels of dissolved salts.
- Add enough of organic matter to your soil
Adding organic matter to your soil, especially through applications of compost, will over time help make your soil less saline. This is because organic matter can trap salts and slowly release them over time in quantities that plants can take-up.
- Mulch your vegetable garden
Soil salinity increases under drought conditions because there isn’t enough water flowing through the soil to carry away salts. Mulching your vegetable garden when it’s very warm and under drought-like conditions will help keep your soil moist at all times. This will allow salts to be continuously carried away rather than accumulate in the soil.
- Grow vegetables and varieties that are tolerant of saline conditions
In certain coastal and arid areas removing excess salts from the soil may not be possible. A way of adapting to these conditions is to grow vegetables and varieties that are more tolerant of saline conditions.
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- High Salt Tolerance: Beets, Bell Pepper, Broccoli, Spinach and Tomato
- Moderate Salt Tolerance: Carrot, Cauliflower, Potato, Sweet Corn
- Low Salt Tolerance: Beans, Celery, Cucumber, Radish
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Source: Salt Tolerant Vegetable Gardening, University of Florida
Even among types of vegetables that are more tolerant there will be certain varieties that are more tolerant of saline conditions and others. You can ask vegetable gardeners and farmers in your area or your local agricultural extension office to help you identify these varieties.
- Add gypsum and lime to your soil
Adding gypsum and lime to your soil will help you remove any excess salts from your soil. The gypsum or lime that is added will only help excess salts in the soil become more soluble and water must flow through the soil after application to remove the soluble salts.
This method works best for more sandy soil because of the ease of water to move through these types of soils. In addition, gypsum will add calcium and sulphur, while lime will add calcium and magnesium, all of which are micronutrients needed by plants. As with any soil amendment, you should only add a little at a time.
- Grow vegetables in containers or raised beds
If you have tried all the methods mentioned above and have not seen any improvement or can’t wait to start your own vegetable garden, you can always use containers or raised beds that are not connected to the soil to grow your vegetables. You will then be able to grow your vegetables in potting soil or a soilless medium, such as cocopeat, so that you won’t have to worry about your saline soil for a while.
Soil salinity can create problems in any vegetable garden, especially under drought conditions. Taking steps to minimize the build-up of salts in your garden soil requires only basic practices such as adding enough organic matter and mulching.
Coastal, arid, semi-arid, and other climate change affected areas, getting rid of excess salts from the soil is not possible. Despite this, more salt tolerant vegetables may be able to be grown in these areas, while the soil can be ameliorated using gypsum or lime. If all else fails, you can grow your vegetables in containers or raised beds that are disconnected from the soil.