What's the difference between compost & fertilizer?

Hi Sprout

Someone will come along with a better definition, but I think compost is organic matter that has broken down.

Manure is, well, manure...

Fertiliser is anything that makes your soil more fertile - I guess it could be organic or inorganic.

Manure and compost are both types of fertiliser, as is bonemeal, or any of a wide range of chemicals you can buy, organic or artificial.

Coffee Grounds can be used as a fertiliser directly, but it can also be used in the composting process.

In my mind (which isn't necessarily a good thing) fertilizer is something which feeds plants or soil and compost is a soil alternative.

Manure if fresh can be used as a feed (be careful as it can burn young plants and cause scab on spuds and forking of root veg), but you could make a plant tea which could then be diluted. Homemade compost can be used to feed the soil/ make it nutrient rich. Decaying plants and plant tea can act as a fertilizer, worm poo, blood fish bone.

Well rotted manure can be used as a soil alternative, as well as homemade compost but the older it is the more nutrients are lost and the less it is any good as a feed. Shop bought multi purpose compost only tends to have 6 weeks worth of nutrients so is pretty much just compost.

I am probably wrong, but that is how it works in my mind

So if I get hold of a horse manure (hopefully this weekend), when is the best time to use it ?

Whenever I've used it when planting potatoes before, I've put a layer in the bottom of the trench, put a thin layer of soil over it and then stuck the potatoes on top of that.

Is it okay to use fresh in that way ?

^^^As far as I am aware the worst fresh poo will do to spuds is cause scab which means they will be no good for storing. Depends on how many spuds you are growing and if you intend to store lots, if you are it is not worth the risk IMO.

IMO - home-made or council compost, green manures and animal manures are soil conditioners which also add low levels of nutrients. You need to regularly add lots of compost/manure to make soil fertile enough to grow without adding fertiliser.

Fertilisers are concentrated feeds for soil that may be lacking in nutrients, they can be organic or not, but don't usually improve the soil's condition. I have difficulty adding enough compost/manure so find I need to use fertiliser for my soil to yield good crops.

Shop bought composts are soil replacements with variable, according to brand - but usually low, levels of fertilisers included in the mix.

So is there ever a point at which you have soil that is fertile enough and in good enough condition that there's not much value in continuing to add to it ever again, or do the things that are growing constantly take nutrients out that need replacing ?

That's exactly how it works. If you start growing in really good soil, without further additions yields will fall within a few years - so you'd need to start adding fertiliser, or more manure again.

From RHS:

Fertilisers
Fertilisers are concentrated sources of plant nutrients, usually in compact form such as pellets, granules, powders or liquids. They are used to improve plant growth and yields.

Why use fertilisers?
Fertilisers are used to improve plant growth. The faster growing the plant, the more it will benefit from fertiliser application. If you have a healthy soil, it is often not necessary to use fertilisers, but using them may produce a showier display of blooms or a higher yield of produce from edible crops.

Fertilisers are also used where plants are showing signs of nutrient deficiency, usually shown by leaf yellowing or discolouration in varying patterns for different nutrients.

Remember that healthy soil structure and pH are just as important as fertiliser application in the prevention of plant nutrient deficiencies. Soil conditioners such as manure and compost help the soil to form into crumbs with spaces for air and water between them, making nutrients, water and air all more available to plant roots. Lime is added to remedy acidity.

What are fertilisers?
Fertilisers contain concentrated sources of plant nutrients in chemical or organic form. Most contain major plant nutrients, which plants need in relatively large amounts. Some also contain trace elements, which plants only need in tiny amounts.

Most fertilisers are based on the three major plant nutrients:
Nitrogen (N): For green leafy growth
Phosphorus (P): For healthy root and shoot growth
Potassium (K): For flowering, fruiting and general hardiness

All fertilisers should quote their N:P:K ratio on the product packaging. For example, a ratio of 20:20:20 indicates a balanced fertiliser (in this instance Chempak formula 3), but a ratio of 10:12:24 would indicate a high potassium fertiliser (in this case Chempak Rose Food). However the N:P:K can be misleading if they refer to phosphates and potash, rather than phosphorus and potassium, see our advice in fertiliser labels explained for more information.

Compost and manure are natural and in the process of breaking down for nature to reclaim, they release healthy amounts of nutrients which are adequate for most plants. However they can be short lived if the soil is poor to start with so you need to pile it on/in and refresh as mulch during the season for best/full effect. Lots of compost will address all poor soil conditions effectively.
Fertiliser is typically concentrated nutrients that release rapidly to be available to the plants, this can be in the form of compost tea (a bag of compost soaked in a bucket of water for a week or so), Comfrey or nettle tea (as before but more smelly), blood fish and bone meal (BFB), Seaweed extract, or indeed the commercially manufactured NPK chemical fertilisers (which are nutrient dense but damage the local beneficial soil life). Epson salt (magnesium sulphate) and potash (or wood fire ash) are more natural and increase the local fertility.
So all these can be used in part to address percieved problems and try to enrich/enhance plant growth, mixtures are good but beware of inorganic costs (not just financial).

Thank you all for the great responses. I understand it all a lot better now

Just noticed your vine name. You have a heck of a name to live up to. She is now sadly departed.

http://www.growfruitandveg.co.uk/gra...ment_5573.html