You have a great resource for enriching your soil with castings and manure if it is well composed. Most Amaryllis "how-to" sites advise using a low nitrogen/ slow release fertilizer, such as a powdered or diluted liquid "bulb or bloom" booster. Recommendations are a 5-10-10 or 6-12-12. I am concerned that composted manure will be too high in nitrogen which encourages foliage growth but not bloom development. There are various fertilizer schedules. One schedule is an application after growth starts, when the blooming is finished and once later in the season. Don't fertilize too late in the season, since you want the foliage to have a short dormancy. Another schedule is a very diluted fertilizer applied at every watering through the growing period. Type in "Fertilizing Amaryllis" for various websites with information.
