Gardening Basics
Garden fertilizers
In the wild, plants take up nutrients from the soil. When the plant dies, these elements are returned to the soil and the cycle repeats itself. However in a garden, fruit, vegetables, flowers and pruning's are removed, depleting the soil of these nutrients. For example potatoes and beans contain large amounts of Potash. A shortage of Potash will reduce the chances of healthy plants in the future, Potash also helps reduce the loss of nitrogen from the soil.
Plants need three main nutrients to help them grow and remain healthy:
- Nitrogen (N) (i.e. lawn feed) used to green up a lawn and also promotes leaves and shoots in shrubs and trees.
- Phosphorus (P) (i.e. Bonemeal) provide a great start for newly planted shrubs, vegetables, trees and bulbs, it's also good to use in spring to promote strong, healthy root development.
- Potassium (K) (i.e. tomato feed) is required by most plants in the greatest amount. It's used before and during the flowering season, to encourage the plant to set flowers and develop fruit. It also controls the water content and transportation of other plant foods from roots to shoots. Ideal on fruit bushes/trees, roses, tomatoes and hanging baskets. Note. Potash (K20 - Potassium oxide) is regularly used in gardening, it's a common term for additives containing Potassium.
Bacteria in the soil break these chemicals down into a form that can be taken up by the plant. Trace elements such as Boron (B), Calcium (Ca), Chlorine (Cl), Copper (Cu), Iron (Fe), Magnesium (Mg), Molybdenum (Mo), Manganese (Mn), Nickel (Ni) and Sulphur (S) are also required by plants but in small quantities.
How are fertilizers labeled?
Let's take lawn fertilizer as an example, you'll see on the label:
NPK Fertilizer 10-2-4
This means that there is 10% Nitrogen, 2% Phosphorus and 4% Potassium (in most cases Potassium oxide). There are also trace elements included, these should be labeled separately.
Natural vs Artificial Fertilizers
Natural fertilizers are made from animal or plant material such as chicken and horse manure, bonemeal, blood fish and bone, seaweed and compost. They release nutrients slowly and add 'body' to the soil, improving soil structure, however they can be awkward to apply and may not provide all of the nutrients that a plant may need. Natural fertilizers such as chicken or horse manure are high in nitrates and may scorch plants if used fresh. Dry out chicken manure and use it sparingly around the plants, compost horse manure for at least a season, alternatively add it to the soil when double digging.
Artificial fertilizers are manufactured by a chemical process, they are easy to apply and give a carefully controlled mixture of the 3 main nutrients required by plants. Over use of artificial fertilizers can create an imbalance in the environment and excess nutrients can leech into the water table or nearby streams and rivers.
Notes:
Yellow leaves normally suggests a lack of Nitrogen.
Ash from a bonfire contains water soluble Potassium, mix with water and use on tomatoes and flowers.
Beetroot love sodium.
Don't give Nitrogen to Chili plants - they prefer Potassium.
Blackcurrants need a lot of nitrogen feed and can tolerate it neat.
Feed Mountain Ash (Sorbus) towards the end of summer.
