Composting · Food Garden · Homesteading · Off Grid · Soil care

Composting: Kitchen waste, NPK & Fertilisers

Home Style Composting

Composting is a very important section of any good gardening book – but they all fail to mention how wonderful good ol’ kitchen waste is. Some say it takes too long to break down and that it must be degraded before planting… but that is a bunch of half-truths. Kitchen waste will break down while your plants grow and the plant roots will assist with decomposition. So when you plant new seeds or seedlings – add a little kitchen waste to the planting hole, as you would fertiliser. It also is easier to add kitchen waste directly to the garden, since many gardeners do not have enough space for a compost heap or bin. Composting kitchen waste is very sustainable, since it is readily available, high in nutrients, reduces the waste on landfills and is a way of accessing a free service provided by mother nature to assist with your vegetable gardening efforts.


Composting Bins soil care maintenance


The lowdown: Kitchen waste has an astounding amount of nutrients and breaks down within 1-2 months depending on the season and what you put in the ground. Most things (tea bags, leaf based stuff, whole fruits and vegetables, banana peels) breaks down in 1-2 months, stuff like avocado peels take longer smile emoticon.


B&B – Banana and Beet Lore
Banana peels and beet leaves are some of the the best nutrients from the kitchen (next to comfrey, but that’s not kitchen waste) you can give the soil and the plants – I always aim for high potassium foods – not just for fruit and flowers, but for plant resistance! Earthworms love them too!


Bananas compost


I did a nutrient study to determine, which is the best kitchen waste to add to my home-style composting, focusing on most of the main plant nutrients – NPK, Mg, Ca, Na:

Food (100g) Nutrient Amount of nutrient (mg)
Comfrey (herb) N, P, K 1190, 100, 740
Banana Mg, P, K 27, 22, 358
Beet Greens Ca, Mg, P, K, Na, Fe 117, 70, 41, 762, 226, 2.6
Carrot Greens Ca, P, K, Na 33, 35, 320, 69
Borage (herb) Ca, Mg, P, K, Na 93, 52, 53, 470, 80
Turnip greens Ca, Mg, P, K, Na 190, 31, 42, 296, 40
Orange Peel Ca, Mg, P, K 161, 22, 21, 212
Beans Ca, Mg, P, K, Na, Fe, Zn 37, 33, 129, 332, 25, 1, 1
Peas Ca, Mg, P, K, Na, Fe,  Zn 25, 33, 108, 244, 5, 1.5, 1.2
Squash Ca, Mg, P, K, Na 15, 17, 38, 262, 2
Basil (herb) Ca, Mg, P, K, Fe 177, 64, 56, 295, 3.2


Now I only added the elements in the nutrient table that matter (values of one type of food relative to the trend amongst all the food), do not want to bore you with numbers. So regarding the table, comfrey is best, followed by borage, but these are herbs and need to be grown specifically for composting. So for kitchen waste: Beets, Bananas, Carrot, Basil … I think you get the picture smile emoticon. So no throwing away carrot or beet greens! The earthworms will get you!!


Soil care fertile arable agriculture wormery vermicomposting bluebudgie


Kitchen waste:
Just about anything that is plant based, leaves, roots, shoots, flowers, fruits … seeds! Anything rotten or that you won’t eat (carrot greens) go back into the ground – if it is safe to lick, it goes in!

Just have a large plastic container with a lid in your kitchen that can take about three days worth of kitchen plant material – more than three days sitting it goes really gloopy. Once full, dig a hole in the garden and plop it in there – you can plant immediately once covered. Or put in a ‘drier’. I dry any excess kitchen waste, for which there is no space in the garden – a very large plastic drum (laundry holding size) and put it in the sun – mine takes 1-2 days to dry out to a crisp! Breaks down in a snap when it is dry and then added to the soil.

Soil care fertile arable agriculture kitchen scraps composting ben_kerckx


Kitchen waste you can give to garden in copious amounts:

Banana peels Carrot leaves Beet greens Herb leaves (everything, lavender, basil, sage…) Herb stems Vegetable shavings (after peeling)
Tea bags! Spent coffee Onion leaves Roots (from spinach or lettuce harvesting) Citrus peels Rotten stuff: tomatoes, peppers, apples…
Spent spices Flowers (rose petals, squash flowers) Turnip and radish greens Peels (pineapple, squash, carrots, potato)


Basically anything that is plant-based can go into the ground – do not bother with processed foods like bread, cheese – as these have little nutrient value for plants in terms of NPK. If you do throw whole fruits (with seeds) into the ground, expect to have some germinate – simply pluck them out and throw them back onto the soil, if you do not want to keep the plants they produce.

I always add some compost and fertiliser to the soil in addition to the kitchen waste (every month during summer, every two during winter).

Compost should be well degraded as to not burn the plants, so use ‘diluted’ add about half the volume of compost to the soil you want.

I also add wood ash to my garden regularly as it contains a lot of potassium and other wonderful bioavailable nutrients for the garden… also used as cutworm control.


Wood ash potash composting


You can check out the Talborne Organics website for their wonderful range of organic fertilisers and pest control productsFor vegetables and fruits I would recommend the Vita – Flower & Fruit, which is a slow release 3:1:5 NPK that you can add to your plots, whereas the Biogrow Biotrissol is a liquid fertiliser with similar NPK ratios of 3:2:5 (the liquid one you can add every two weeks at half strength to all actively growing fruit and veg). Talborne Organics have an extensive list of distributors around South Africa and should be easy to come by.


Talborne Organics Website

9 thoughts on “Composting: Kitchen waste, NPK & Fertilisers

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