Feed the Soil - Not the Plants

Fertilisers are something that most of you will have a strong opinion on, whether you're in favour or against, however it's a term that can cause some confusion.

The first thing I want to clear up is that a fertiliser is anything that you add to the soil specifically to provide one or more nutrients essential to plant growth.  It can be an organic or an inorganic compound and can be natural or synthetic in origin.


However, commercial fertilisers are required to meet certain nutrient levels before they can claim to be a "fertiliser".  As a result, certain products with lower nutrient levels tend to be referred to as "tonics".  They still provide the nutrients that your plants need and, unless you've been neglecting your soil, they'll be fine for the home gardener.

Plants need a range of macro and micro-nutrients (otherwise known as trace nutrients / minerals) for healthy growth and reproduction.  These nutrients are available in all soils to a greater or lesser degree, depending on the parent materials of the soil and the processes it has undergone.  The macro-nutrients are generally available in larger quantities and are also required in larger quantities, the micro-nutrients are usually available in lesser quantities and less is generally required by the plants.

Fertilisers are used when there is a shortage of a particular nutrient, or group of nutrients, required for growth.

When a plant or a crop looks crook, many of us are guilty of giving them a good dose of synthetic N:P:K fertiliser without really understanding what the plant needs or how we should really go about treating it.

But what it is important to understand is that any plant health problems, whether it's a nutrient deficiency or an attack from a particular pathogen or pest, will have it's roots in the soil.

If you feed and nurture the soil, then it will create a healthy, balanced, nutrient rich environment in which to grow your plants.  Some will never need any additional fertilisers as a result.

For those that do, organic fertilisers can be used to both feed your soil and your plants.

Examples of organic fertilisers that you can try, both at home and on the farm are:

• manure - cow, goat, horse, pig, poultry, sheep and mixes of the lot are all available to purchase commercially.  In some places, you can even by Zoo Poo, for a more exotic manure mix:)
• Blood and bone meal - various mixes of this are available, including meat and bone, or on their own.  Occasionally these include added synthetic nutrients, so read the packet;
• Fish meals, or liquid emulsions - often have added nutrients and are great for feeding the soil and well as the plants. My favourite is Powerfeed, which also includes humic acid so works well as a soil improver, and it doesn't smell too bad!
• Seaweed products - there are loads of these on the market and they're generally referred to as plant tonics.  Seasol, the sibling to Powerfeed, is a great when establishing new plants, for maintaining health and vigour, promoting flowering and fruiting etc;
• Compost - I like to consider this more of a soil improver than a fertiliser, as it's main purpose is to add organic matter to the soil, but it does of course add nutrients available for plants;
• Compost teas / manure teas - these are something everyone should be doing at home!  Allowing a bag of compost or manure to sit in a bucket of water for a couple of days and then using the resulting tea on your garden is a great way to provide readily available soluble nutrients, and of course improve your soil with the addition of organic matter at the same time.  Makes a good foliar feed too :)
• Worm castings / vermicompost - another source of organic matter for your soil, but also one that is rich in nutrients.  Sprinkling this around your garden beds is a great way to give plants a boost;
• Worm "wee" - use in the same way as compost / manure teas, but can be stronger so remember to dilute!
• Urea - actually available as a manufactured product, honest, but you can try peeing on your garden if you're not concerned about the neighbours...
• Molasses - not something I would consider as a fertiliser, but it does provide valuable soil microorganisms with a great food source, giving all the important processes taking place in your soil a huge boost.  I use this in combination with Seasol and Powerfeed on a regular basis, and also add some when making compost teas as well as watering my compost heaps with it.

Read the post on organic matter to find out more about how adding organic matter can help improve your soil's fertility.