Feeding veggies through the season

Not all vegetables eat the same way. A lettuce wants steady nitrogen for soft leaves. A tomato wants feeding at planting, then potassium when it flowers. Carrots do best with very little. Peas and beans make much of their own nitrogen. Feed each group the way it likes and you'll get better crops for less fertiliser.

Start with the soil

Whatever you're growing, the best feeding starts before you plant.

• Spread compost over the bed, a few centimetres deep, and lightly mix it into the top layer.
• Add a slow-release organic fertiliser for hungry crops, such as pelleted chicken manure or a complete organic blend, following the label.
• Water it in and wait a week or two before planting if you've used fresh or strong manure.
• Mulch once seedlings are up.

Good soil with plenty of organic matter does a lot of the feeding for you.

Heavy feeders and light feeders

Leafy greens: nitrogen, little and often

Lettuce, silverbeet, spinach, kale, Asian greens and celery grow fast and are all leaf, so they want a steady supply of nitrogen.

• Start with compost and a slow-release organic fertiliser in the bed.
• Give a liquid feed every one to two weeks while they're growing. Fish emulsion, a seaweed-and-fish blend, or diluted worm farm liquid all suit.
• Pick often. Leafy greens that keep growing quickly taste sweeter and are slower to bolt.
• Pale, yellowing older leaves usually mean they need more nitrogen.

Avoid one big dose. Too much nitrogen at once can scorch roots and gives soft growth that aphids love.

Fruiting crops: switch to potassium once flowering

Tomatoes, capsicum, chilli, eggplant, zucchini, cucumber, pumpkin and melons need good growth early, then plenty of potassium to flower and set fruit.

At planting: dig in compost and a slow-release fertiliser. Tomatoes and zucchini are hungry, so be generous with compost.

While growing: a balanced liquid feed every two weeks or so.

Once flowering starts: switch to a feed higher in potassium, such as a tomato or fruit-and-flower fertiliser, or add a little sulfate of potash. Keep feeding every two weeks while plants are fruiting.

Watch out for:

• Too much nitrogen. Lots of leaves but few flowers or fruit is the classic sign. Stop the nitrogen and switch to a potassium feed.
• Blossom end rot. A dark, sunken patch on the bottom of tomatoes or capsicums. It's linked to calcium, but the usual cause in home gardens is uneven watering, not a lack of calcium in the soil. Water deeply and regularly, and mulch well.

Root crops: go easy

Carrots, parsnips, beetroot, radish, turnips, onions and garlic need much less feeding than you might think.

• Go easy on nitrogen. Too much gives lush tops and small or poor roots.
• No fresh manure. Fresh manure, or lots of strong fertiliser, in the bed is a well-known cause of forked, hairy carrots and parsnips. Plant root crops in a bed that was well fed for a previous crop, or use only well-rotted compost.
• Loose soil matters more than food. Remove stones and break up clods so roots can grow straight down.
• Onions and garlic benefit from compost at planting and a light feed in late winter or early spring, but stop feeding as the bulbs start to swell.

Legumes: little or no nitrogen

Peas, beans and broad beans work with soil bacteria that live in nodules on their roots. These bacteria take nitrogen from the air and share it with the plant.

• Skip high-nitrogen fertilisers. They can lead to lots of leaves and fewer pods, and the plants don't need them.
• Compost at planting is usually enough. A little potassium can help flowering.
• After harvest, cut the plants off at ground level and leave the roots in the soil. Follow with a leafy or heavy-feeding crop.

Side-dressing with compost

Side-dressing means adding food along the side of a row or around a plant during the season, instead of digging it in. It's an easy way to keep heavy feeders going.

1. Pull back the mulch.
2. Spread a band of compost, or a small handful of pelleted manure, a little way out from the stem.
3. Water it in.
4. Put the mulch back.

Good times to side-dress:

• Tomatoes, when the first fruit set.
• Corn, when plants are about knee high.
• Zucchini and pumpkin, once they start fruiting.
• Brassicas, about a month after planting.

A simple feeding calendar

Rotate your crops

Moving crop families around the garden each season helps balance feeding. A simple pattern is to follow legumes with leafy greens or heavy feeders, then root crops, then legumes again. Each crop uses what the one before left behind.