Good question, I don't think strawberries need as much feeding as other, more hungry fruit and vegetable crops. You also have to be careful not to feed them too much because they might produce to much foliage at the expense of fruits. I would sprinkle a couple of handfuls of bonemeal
per m2 into the soil at planting time. Then once you have picked all the fruit, sprinkle a couple of handfuls of potash
per m2 amongst the strawberry patch.