How to Fertilize a Raised Bed Garden

Raised beds filled with a compost-rich mix often have enough nutrients for a first crop of lettuce or beans. Fruiting crops (tomatoes, peppers, squash) may still run short of nitrogen or potassium midseason. The mistake is dumping a high-nitrogen product every Saturday.

A working order of operations

1. Build or refresh the bed with compost mixed into the soil, not only a dusting on top. See soil mix.
2. If plants were disappointing last year, get a soil test through your cooperative extension. It is the least guessy option in the US.
3. If you fertilize, match the bag to the crop. The fertilizer calculator does that without asking you to know N-P-K first: leafy crops lean nitrogen, fruiting crops lean potassium, mixed beds stay balanced.
4. If you already have a bag, the same calculator turns the three numbers into kitchen spoons (tsp or Tbsp). Pick Light, Typical, or Stronger — you do not need a nitrogen rate. When that estimate disagrees with the label, follow the label.
5. Water fertilizer into moist soil. Keep granules out of the crown of the plant.

Compost vs fertilizer

Compost feeds soil life and adds a slow trickle of nutrients. It is not a precise N-P-K source. A 1-inch top-dress (see the compost calculator) is a reasonable annual habit for many beds. Fertilizer is for a measured extra push or a documented deficiency.

Midseason side-dressing

Tomatoes and peppers often get a side-dress when the first fruit sets, not the day you transplant. Keep nitrogen moderate. If leaves are deep green and plants are lush but flower poorly, more nitrogen is the wrong move.

Regional note: alkaline soils in parts of the West can lock up some nutrients; acidic soils in parts of the East have different issues. A test beats copying a rate from another state.