Fertilisers: A Basic Guide

I’ve only ever used Tomorite and chicken manure pellets, so I thought I’d take a look at which fertilisers work best depending on the vegetables/fruit I have been trying to grow. I found this information on the DT Brown website here. It seems clear enough. Nitrogen (N) produces green leafy growth and foliage; Phosphorus (P) helps root and shoot growth; Potassium (K) is for flower, fruit and general hardiness

An Introduction To N:P:K

During the growing season plants absorb important nutrients and minerals from the soil, these need to be replaced if your plot is to maintain a high level of productivity and yield. Most general-purpose fertilisers have an N:P:K rating which relates to the three primary elements needed for healthy plant growth, the higher the rating the more of that element exists within the fertiliser.

Nitrogen (N)-Supports the growth of the vegetative parts of plants, stems and leaves. It is vital for the production of chlorophyll, which allows plants to carry out photosynthesis. Leafy vegetables such as spinach, cabbage and lettuce have a high nitrogen requirement as does lawn grass. Lack of nitrogen causes poor, stunted growth with spindly stems and yellow or discoloured leaves. Nitrogen washes out of the soil so feeds need to be applied little and often, especially during the growing season.

Phosphorus (P)- Stimulates seed germination and root development, increases stem strength and improves fl ower formation. Root vegetables need plenty of Phosphorous to aid development. Lack of phosphorus causes poor, stunted growth. Plants produce little or no fl owers, have weak root systems or a bright green or purplish cast.

Potassium (K)- Essential for flower and fruit production and improves drought, pest and disease resistance. Often referred to as the “quality element,” because of its importance to many of the features associated with quality, such as size, shape, colour, and taste. Potatoes, fruit and tomatoes all need high levels of Potassium to crop well. Plants low in potassium are stunted in growth and provide lower yields. Excessive levels of potassium can lead to magnesium and calcium deficiencies. Minerals and trace elements are also an important requirement for good plant health. Over time, with each and every harvest, the soil is depleted of these vital ingredients and they also need replacing.

Some Fertilisers and their approximate N-P-K Ratios (full list povided by SAGA here)

  • Chicken manure pellets = 4-2-1 (good for brassicas and salad leaves; and also hellebores)
  • Growmore = 7-7-7 (nitrogen levels too high for tomatoes but OK for potatoes)
  • Tomorite = 4-3-8 (high potash – good for tomatoes and container grown plants)
  • Blood, fish and bone = 3-9-3
  • Seaweed = ratios vary, so check the packaging

Recipe for Homemade Tomato Fertilizer

  1. one gallon, or larger, container such as a bucket.
  2. 1/2 gallon of compost.
  3. 2 cups of rabbit droppings.
  4. 1/2 cup of human & pet hair, cut into small pieces.
  5. 2 cups of dried alfalfa leaves or alfalfa pellets.
  6. 1 cup of dried, crushed egg shells.
  7. 1 cup of used, dried tea or coffee grounds.

I don’t think I’ll be making this home-made fertiliser recipe any time soon