How to Fertilise a Vegetable Garden
Vegetable fertilising should be approached for two different purposes, each working towards the same goal. Healthy, vigorous and productive plants. This is either fertilising in preparation for planting, or, fertilising maturing plants to improve growth and health. Depending on the plants, different approaches are needed.
Basically, we need to fertilise the vegetable beds in preparation for planting. This is done in advance of planting and then we need (in some circumstances) to fertilise plants when they are growing/producing. This page will deal with different types of fertilisers suitable for vegetable gardens and fertilising beds in preparation. Fertilising specific crops is dealt with on the plants page under each type as well as in crop rotation.
Natural v.s Chemical
Fertilisers basically come from two sources, either natural sources such as animal manures, compost bins (not strictly fertiliser), worm farms and naturally occuring minerals etc or from artificial chemically produced sources. Both are readily available at any good garden supplier or hardware store.
I'm not going to lecture you on the pro's of organic vegetable gardening and natural fertilisers versus the perceived "evils" of chemical fertilisers. What you choose to use is entirely up to you. What do I prefer? Well I mostly stick to natural sources. Why? well in my opinion, if used properly, they are just as effective and generally cheaper.
Let's look at why we fertilise first, then what job each does.
Plants use minerals in the soil, often referred to as trace elements, water and nitrogen, phosporus and potassium to grow. Most chemical fertiliser packets display the ratio of the contents of these by their chemical symbols (NPK) and show them as the NPK ratio. Don't worry, there's no chemical/science lesson coming here.
The basics you need to know are that Nitrogen encourages green leafy growth and potassium, also called potash, promotes flowering. So anything you want to grow, where the main part you eat is the leaf, like say a lettuce or silverbeet, spinach etc loves nitrogen and anything that needs a flower to produce the part you eat, such as tomatoes and other fruits, also need nitrogen, but a reasonable dose of potassium, to encourage the flowers to make the fruit.
Natural sources of vegetable garden fertilisers basically come from the following:
Blood and Bone mixes
Now these sources naturally have differing levels of strength and get used for different reasons.
Chicken manure is typically high in Nitrogen and can be quite strong so it has to be used with care. Cow and Horse manure are weaker and are generally used as soil conditioners and aren't usually a great food source for plants. Care has to be used if you source Horse manure from a stable as it is usually saturated in urine and can burn plants. It should be left in a pile to compost down for a few weeks. Sheep Manure, often affectionately referred to as "garden marbles" because of their shape is somewhere in the middle. Blood and bone mixes are sold commercially as a powder and can vary in "nutritional value" so check the labels and compare brands.
How much to use depends on the size of your bed, what you're planting and when.
Let's look at my vegetable garden beds as an example.
Each is around 10ft x 5 ft.(2.4mtr x 1.5mtr) If I was preparing a bed for spring/summer planting of leaf crops, like lettuce, cabbage, broccoli, cauliflower etc. I would use the following:
1 sack of sheep manure Around 1-2 kg's pelletised chicken manure About 500g to 1kg of blood and bone. spread evenly over the top of the bed, lightly raked in, watered and then heavily mulched.
As we have so much information related to fertilising, we have broken the details into two further pages depending on the type of fertilier