[tweetthis]13 Key Nutrients for Plants – #2 Phosphorous[/tweetthis]

Soil testing is an important activity for a successful garden. Soil stewardship is an ongoing process, where you test and amend, grow some stuff, then test, amend and grow some stuff….and so on. Focus on building soil tilth so it can really hold and make available to the plants all the important nutrients. You do this in part by adding compost, manure, rock dust, bone meal, kelp & fish emulsions. Read this article series to learn more about each of the 13 key nutrients for your garden.


Phosphorus is important to early root development, especially important when the soil is cool. It is crucial to leaf and fruit production and is required to perform cellular division and for energy transformation. Phosphorus is easily leached from soilless mixtures and soils high in peat and it needs to be provided continuously in those situations. The quantity required is usually less than nitrogen.

A plant that is deficient in phosphorous will be stunted, with water-soaked patches on older leaves. New leaves will be small, stiff and dark coloured. If this is not corrected the leaves will shrivel up and dry out.

To correct a deficiency of phosphorous
  • add colloidal phosphate to the soil the year prior to when you will grow in that location
  • Add fish bone meal to the soil to add direct phosphorous
    note this will add calcium as well.

Leaves showing an orange-yellow colour between the veins which remain green, is a potential sign of phosphorous toxicity. A soil that has too much phosphorous may develop deficiencies of other nutrients, in particular zinc and iron, however, toxicity is not generally a problem except sometimes in a hydroponic system.

To offset excessive phosphorous
  • create a strategy to boost other nutrients, especially nitrogen without using manure (because manure is very high in phosphorous)
  • plant beans and peas (legumes) which will fix nitrogen and make it available to other plants without introducing phosphorous or potassium
  • both cucumbers and tomatoes like slightly less nitrogen versus phosphorous and could help use up some of the phosphorous in the soil
  • Root vegetables like parsnips, carrots, beets and radishes all require phosphorous and potassium
  • Clover and vetch (do not eat vetch it is poisonous) can be used to balance the nutrients in the soil
  • Design a rotation something like this: Carrots, Beets, Radishes, Clover, Parsnip, Beans, Vetch (do not eat vetch it is poisonous), Peas, Cucumber, Tomato

[tweetthis]Learn about Phosphorous in plants![/tweetthis]