June 23rd, 2020 by Sarah Miles

Growing your own vegetables can be extremely satisfying, whether you fancy becoming more self-sustaining, want more control over the quality of the food that you eat, or just for a project with the children. If you are a keen grower of vegetables or just getting started, you’ll no doubt be looking for tips on improving your crop. You may already be aware that iron sulphate can be used on your lawn to make it lusher and greener, as well as stronger and more resistant to pests, but can it also be used on your veg patch?

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What does iron sulphate do for plants?

In order to understand the range of applications, it is interesting to first of all look at how iron sulphate works in terms of helping plants grow. It’s all about soil quality. You don’t have to be green-fingered to realise that the soil in which your plants grow, provides everything they need in terms of nutrients. Look after the soil and you will look after your plants.

Soil has a pH level which tells you how acidic or alkaline it is. As you probably remember from those school chemistry lessons, a pH of 7.0 is neutral. pH 6 and lower are increasingly acidic. pH 8.0 and higher are increasingly alkaline. Most vegetables and flowers grow best in soil that has a pH between 6.0 and 7.0, so slightly acidic to neutral. Vegetables such as potatoes, aubergines, tomatoes, peppers, squash and kale all thrive well in slightly acidic soil.

Plants need iron: it is vital to functions such as enzyme and chlorophyll production. While iron can still be present in alkaline soil, the alkaline binds iron particles and this makes it unavailable to plants.

Adding iron sulphate to the soil will make it more acidic and therefore allow plants to absorb iron more effectively.

Is iron sulphate suitable for vegetable patches?

The answer to the question, therefore, is yes it can help but it’s important to approach it scientifically. That means using it in an appropriate way according to the pH level of your soil. This isn’t as complicated as it sounds as it’s quite easy to measure the pH level using a soil testing kit which is readily available for just a few pounds. If your soil has a pH level of 8.0 or over, and therefore alkaline, you can use iron sulphate to increase the acidity to an appropriate level.

Signs that you may need iron sulphate

Before you even test your soil, there may be some visual clues that your plants are lacking in iron. Yellow leaves are a common indicator that this may be an issue. Iron chlorosis is caused by iron deficiency. While there can be other causes of yellow leaves, such as insufficient nitrogen, iron chlorosis is characterised by the yellowing beginning with new plant growth rather than existing leaves turning yellow.

How to apply iron sulphate

Always check the pH level of your soil first so you know how much more acidic you need to make it. You don’t want to make it too acidic; aim for a pH of 6.0 to 7.0. Iron sulphate comes in granule or powder form which can simply be scattered over the soil and then watered in. The amount you need can be determined by following the manufacturer’s instructions in line with the acidity you are aiming to achieve.

Iron sulphate can be caustic so ideally wear gloves and eye protection.

The best time to apply iron sulphate is from the spring onwards, to prepare your soil for the growing season. Keep checking the pH level of your soil and, if required, you can reapply every 4-6 weeks.

This may seem like quite a lot of effort but you will be truly rewarded in the quality and size of the vegetables that you produce!