If you're using dry amendments like fish meal or alfalfa meal, it's much easier to just scratch them lightly in to the surface of your soil or to add them with a handful of good compost or earthworm castings. No need to make a tea in my opinion.
As far as your question regarding availability, that depends on the amendment and the moisture content of the soil and the biology in the soil among other things. Potassium sulfate for instance will be readily available, whereas feather meal will provide slow release nitrogen over a period of weeks. In general, most organic amendments will show with the plant within 5-10 days as a real rough guideline so if you wait until you have a deficiency then it's an even longer wait to correct it with organic amendments.
As far as your question regarding availability, that depends on the amendment and the moisture content of the soil and the biology in the soil among other things. Potassium sulfate for instance will be readily available, whereas feather meal will provide slow release nitrogen over a period of weeks. In general, most organic amendments will show with the plant within 5-10 days as a real rough guideline so if you wait until you have a deficiency then it's an even longer wait to correct it with organic amendments.
