Side dressing gives extra nutrients to vegetable crops so that they can produce to their full potential.
To side dress create a furrow 1 to 2 inches deep along a row of plants or in a circle around each individual plant. Create the furrow just beyond the plant’s drip line (the drip line is the distance from the central stem of a plant to the end of its widest branches). Apply the fertilizer in the furrow and cover with soil.
Side dressings include solids such as granular fertilizers, aged compost and manure, bone meal, and rock phosphate and also liquid fertilizers and fish or seaweed emulsion or compost and manure tea.
Side dressing is commonly done when plants need extra nutrients for growth–at flowering or fruiting time and in the second half of the growing season. From midseason on vegetable crops make rapid growth and quickly use nutrients put in place before sowing or transplanting.
Side dressing also resupplies nitrogen, phosphorus, potassium, and trace elements leached form root zone by irrigation.
How Much to Side Dress Vegetables
One handful of good compost is sufficient to side dress most vegetable plants. That is equal to about one tablespoon of 5-10-10 fertilizer. Adding liquid fertilizers to your watering can is an easy way to side dress. A cupful of compost tea is a good side dressing.
It is important to apply commercial fertilizers according to the instructions on bags or bottles. Over fertilized vegetables tend to be less productive.
Fertilizers should not be placed right next to the stem of a plant; they might burn the roots. Fertilizers side dressed outside the drip line will encourage roots to extend beyond the drip line.
When to Side Dress Vegetables
One side dressing at midseason is usually enough to sustain and encourage a vegetable plant to harvest. Heavy feeding crops–mostly summer fruiting crops that take a long time to mature such as tomatoes, peppers, and eggplants–will benefit from more than one side dressing.
Here are suggested times to side dress vegetables:
Beans: not necessary.
Beets: add bone meal or phosphorous at planting time; side dress when plants are 4 to 5 inches tall.
Beet greens: 2 weeks after leaves appear.
Broccoli: 3 weeks after transplanting and again when heads begin to form.
Brussels sprouts: 3 weeks after transplanting; again when sprouts are marble size.
Cabbage: when the head begins to form; side dressing is not necessary if soil was well fertilized at planting.
Carrots: add bone meal or phosphorous at Cauliflower: when heads begin to form; not necessary if soil was well fertilized at planting.
Celery: 3 weeks after setting out starts; again 6 weeks later.
Chard: after each cutting when substantial leaves are taken from plant.
Corn: 3 weeks after planting or when plants are 8-10 inches tall; again when tassels appear.
Cucumbers: just before vines start to spread and again when blossoms set.
Eggplant: 3 weeks after transplanting and again at blossom time.
Kale: when plants are 6-8inches tall.
Leeks: when plants are 12 inches tall.
Lettuce, head: a few weeks after planting.
Lettuce, loose-leaf: after second and third cuttings for cut-and-come again crops.
Melons: just before vines begin to spread; a week after blossom set; again 3 weeks later.
Okra: at blossom time.
Onion: 3 weeks after setting out; when tops are 4 to 8 inches tall; when bulbs begin to form.
Peas: not necessary.
Peppers: 3 weeks after transplanting; again at blossom time.
Potatoes: before second hilling; when plants bloom.
Pumpkins: when plants start to run; again at blossom time.
Radishes: no need to side dress.
Spinach: when plants are about 1/3 grown; at second and third cuttings for cut-and-come again crops.
Squash, summer: when plants are 6 inches tall; again at blossom time.
Squash, winter: just before vines begin to spread; again at blossom time.
Sweet potatoes: before second hilling.
Tomatoes: 2 to 3 weeks after transplanting; at blossom time; before first picking; 2 weeks after first picking–always light on nitrogen.
Turnips: add bone meal or phosphorous at planting time.
Zucchini: at blossom time.