A few thoughts on fertiliser

There's a lot of do's and don't with fertilisers and many ways to save money on what can be outrageous prices.

Very basically, (as this is a complete science):-  (organic growers look away now)

N, P & K - the constituent and basic parts of a fertiliser.

N is Nitrogen - plants need this for leafy, green, lush growth

P is for Phosphorus and this gives plants what they need for germination and root growth

K is Potassium and this is needed for flowering and fruiting.

Nitrogen can get washed out of the soil with rain and watering quite easily whereas the other two can remain in the soil or compost from one season to the next.

If you're serious a soil test will tell you how much or how little you have in your own soil.

Apart from NPK you need trace elements, of which there are many, for really good, healthy plant growth.

We all know nitrogen because we feed our lawns with nitrogen fertilizers and this gives that quick, green, lush growth.  Fine for lawns but too much green lush growth on fruiting vegetables and flowers will overpower the plants and stop them producing what it is it's supposed to produce - food and flowers.

Phosphorus sounds like something explosive but good root growth means a healthy plant able to take up the other nutrients and water from the soil.  The advent of products like Nutrimate and Rootgrow Mycorrhizal Fungi which aid the plant to maximise it's uptake of nutrients is revolutionizing growing gardening, especially vegetable gardening.  Strong roots = healthy plant = maximum chance for a top crop.

So, we're adding root development fertiliser with root development aids/products/substances.

Healthy plants potted on using Rootgrow and planted in soil treated with a general fertiliser.

Potassium is essential for fruiting and flowering and fertiliser rich in potassium are used in the latter stages of growth to enhance colours and to aid fruiting.

A general fertiliser like Growmore has equal parts of N, P & K and these are expressed as percentages of the total, so maybe 7:7:7 meaning 7% nitrogen, 7% phosphorus and 7% potassium.  General fertilisers like this are a good starting point to cast at a handful per square meter a week or so before planting or sowing.

Of course, some 'general' fertilisers can be expressed as 17:17:17 meaning the percentages are higher as a part of the overall product.  Heaven only knows what the remaining ingredients are - I must Google it and find out.

This is where things get interesting because once you move on you will get fertilisers higher in phosphorus than the other two ingredients (quite rare but available) and ones higher in potassium.  These are what are sold as the specialised fertilisers for Strawberries, potatoes, onions etc. and are sold at extreme premiums which is daft, daft, daft.

I found I was paying a fortune for 'potato fertiliser' and decided to see the NPK of a typical one.  I found it to be almost exactly that of Vitax Q4 (5.3:7.5:10 +TE) which is considerably cheaper.  TE are trace elements - the metals etc needed in vital but tiny quantities.

A typical 2.5 kilo pack of 'potato' fertiliser is about £15 whereas the same size Q4 is £6-£8 - half!

I'm not saying they will compare exactly but I do say to look carefully before buying what they market as specialist fertilisers for special crops - other cheaper fertiliser are almost the same.

A good general guide is to start off with a general balanced fertiliser (equal parts of NPK) and once the plants are in flower or ready to fruit switch to a higher potassium feed.  Liquid feeds are better in the latter stages as the uptake is more easily available.

A good green plant is a healthy plant and look out for signs of yellowing - this is either incorrect watering (too much or too little) or a deficiency in something so you need to fertilise/feed.  A soluble seaweed feed sprayed on is great as a pick me up for ailing plants.

As a result of all the farting around of grow bags I'm starting an experiment using Coir (the compressed dust from coconut shells) which is totally lacking in nutrients until nutrients such a Nu-Gro are added.  Commercial growers use this medium in their grow bags and I'm going to give it a try.  A packet of lawn seed mixed with Coir recently cost me cost £20 for 750gms which seemed madness.  I've done my own for under £1.50, giving rise to this little experiment.  I'm going to plant up a raised bed using Coir and Nu-Gro and see what happens.  This will be in a later post.