Once we learnt to how to produce fertilizers for plants, there was a tremendous sprout in their use. Urea was an early entrant in the list of artificially prepared commercial fertilizer. Though it has proved its usefulness time and again, but now experts are of the view that man-made fertilisers do not provide the much-needed micronutrients to orchids. As a result, we now see a shift in use towards bio-fertilizers or natural fertilisers. The process of adding natural fertilizers to supplement plant growth is known by the name of ‘green manuring’.
Coming back to urea, it is used to supply the essential nutrient - Nitrogen. It is usually given in liquid form. The question now arises whether biological fertilisers can replace urea or not? The answer for that is: Yes, it can be replaced and there are a number of options. We have legumes, they are a good source of nitrogen. Dried legumes stubs (left over portion of the plant after harvesting) can be mixed with the growth media and nitrogen will get released as the plant degrades. Manure mixed with remains of nitrogen-fixing plants such as peanuts, soybeans, fenugreek, clover and other such plants can provide nitrogen to your orchids.
Another example of bio-fertilizer is Azolla. Azolla also captures atmospheric nitrogen like the legumes. Dried Azolla mixed with the growth media can serve as a good source of nitrogen. Unlike legumes, Azolla can be grown in a small area. Used tea bags and coffee grounds and filters also provide nitrogen.
The advantage of these bio-fertilizers is that along with much needed nitrogen; these also supply the micronutrients that are quite important but are required in very small quantities. When the orchids get fertilised by urea, the orchid only get nitrogen and the much needed micronutrients become deficient in the orchids. Unlike urea where much of the nitrogen released is not used by the orchids but gets leached away and thus gets wasted, when bio-fertilizers are added to the growth medium not only are the nutrients released slowly and the orchid can absorb it according to its need, but orchids also received much-needed micronutrients that are just as essential as those nutrients that are required in large quantities.