6 key tips for fertilizing your garden with nitrogen

Nitrogen is one of three primary plant nutrients. Read on for key tips to using it in your garden to give your plants the nutrients they need.

Airborne nitrogen can be used by nitrogen-fixing legumes, but most plants must take it up from the soil. Nitrogen is water soluble and is absorbed rapidly, so it must be replenished regularly.

• The best organic sources of nitrogen are manure, bloodmeal, cottonseed meal, fish emulsion, alfalfa meal and soybean meal.
• Good sources you can find in your own backyard are rich compost and fresh grass clippings.

Grow green manure crops, such as clover, rye or various vetches and peas, to add nitrogen to your soil.

• Sow seeds wherever you want to enrich the soil and let the plants grow to 15 centimetres tall.
• Cut them to the soil line, then turn under.
• They will decay rapidly to release nitrogen, but wait at least a week before planting.

Poultry feathers make a nitrogen-rich fertilizer.

• Place them in a tub and top with a plastic screen, using a few stones to hold them down.
• Cover with water and steep in a shady spot for two months, then strain the liquid and use it to fertilize plants.

• Get a jump on spring by applying an organic nitrogen source in late fall.

It will break down slowly and be available in the soil by planting time the following year.

You'll know you've applied excessive nitrogen if blossoms are sparse and foliage grows too fast and lush, which makes plants more vulnerable to pests, diseases and environmental stress.

• There is no antidote; rain and frequent watering will eventually wash nitrogen away and help the plants recover.

There's no need to dig nitrogen fertilizer into the soil around actively growing plants. Water it in or let the rain do it for you.

Alfalfa meal

• Source: Alfalfa by-products
• Content: 5%
• Application rate: 2.5 kg per 9 square metres

Bloodmeal

• Source: By-product of meat processing
• Content: 15%
• Application rate: 1.5 kg per 9 square metres

Cottonseed meal

• Source: Dehulled cottonseed
• Content: 6%
• Application rate: 1 to 2.5 kg per 9 square metres

Fish emulsion

• Source: By-product of fish processing
• Content: 4%
• Application rate: 1 part to 20 parts water

Fishmeal

• Source: By-product of fish processing
• Content: 10%
• Application rate: 2.5 kg per 9 square metres

Manure

• Source: Animal waste
• Content: 2 to 13%
• Application rate: 1.5 to 2.5 kg per 9 square metres

Soybean meal

• Source: Soybean by-products
• Content: 7%
• Application rate: 2.5 kg per 9 square metres