As we all know compost is nothing but decayed organic material used as fertilizer for growing plants. We also now know about the nutrients required by plants. Now all we have to do is add these nutrients to compost and eventually add the compost to the soil. But the question is to identify which organic material contains which element!
I’ll give you a very brief identification methodology:
Carbon : Anything brown in color contains carbon. Let’s take for example a leaf. Leaf when green in color does not contain much carbon but a dried leaf which is brown in color is a very rich source of carbon. Similarly you can use sawdust or rice husk.
Hydrogen & Oxygen : Plants obtain the required quantity of Hydrogen and Oxygen from water(H2O). So keep watering the plants regularly !! 🙂
Nitrogen : Anything green in color has nitrogen in it. So all the green leaves and kitchen waste (which are mainly fruit and vegetable peels) act as an excellent source of nitrogen.
Phosphorous & Potassium : One logic says any fruit or vegetable will have phosphorous and potassium in it because it is utmost necessary for its growth. So if you add any fruit or vegetable to the compost it is sufficient. You need not add fresh fruits and vegetables to the compost. Any leftover or spoiled or unconsumed fruits/vegetable can be added to the compost. This logic applies for all the elements here on. But if you are still not satisfied you can add rock phosphate (directly to the soil) which is an excellent source of phosphorous. You can also add wood ash (directly to the soil) which acts as an excellent source of potassium as well as phosphorus.
Calcium & Magnesium : You can add calcium rich fruits/vegetables like cabbage, broccoli, banana, papaya, sweet potato, etc. I repeat you need not add fresh fruits/veges. You can add their peels or leftovers or the spoiled parts that you will not be consuming.
I would not appreciate you spending even a single penny for making compost!! The whole motto of making a compost is to use all the kitchen and garden waste. Happy Gardening!! 🙂