Sunday, September 19, 2010

Crop Rotation Basics part one, Soil based pathogens

Crop rotation basics consist of designing a planting rotation based on knowing the affects of:-
  1. Soil based pathogens
  2. nutrient  deficiencies
  3. heavy and light feeders
This article will cover the first topic only.

Soil based pathogens

Some plant families are affected by pathogens that build up in the soil in response to its food source i.e. that plant family. Planting members of that family in the same soil repeatedly provides the conditions for that associated pathogen to multiply its population to levels that cause noticeable distress to that family member. Starving that population of pathogens before it numbers increase to problem levels is how you manage soil based pathogens naturally.

Plants families which are affected by soil based pathogens to my knowledge are
  • Brassica
  • Solanum

Brassica also known as the cruciferous family due to the flowers resembling a cross, represent a large portion of cultivated food consists of
·        Horse radish
·        Land cress
·        Ethiopian mustard
·        Kale
·        Collard greens
·        Chinese broccoli
·        Cabbage
·        Brussel sprouts
·        Kohl Rabi
·        Broccoli
·        Broccoflower
·        Broccoli romanesco
·        Cauliflower
·        Wild broccoli
·        Bok Choy
·        Komatsuna
·        Mizuna
·        Mibuna
·        Rapini (broccoli rabe)
·        Chinese cabbage
·        Turnip
·        Rutabaga
·        Canola rapeseed
·        Mustards
·        Tatsoi
·        Rocket
·        Garden cress
·        Watercress
·        Radish
·        Daikon
·        Wasabi

The soil based pathogen that affects this family is called club root
 As the name suggests the roots of the plant swell with infection causing poor uptake of nutrients. Once club root takes hold in the soil it can take in excess of ten years for the pathogen to decline to non affecting levels. Managing the problem once it is present requires starving it of any member of the cruciferous family for a minimum of 4 years or longer if possible. A natural soil soak which may help kill off this pathogen while the soil is being "rotated" consists of rhubarb leaf tea. Application is every three months for a few years and is applied as a soil drench i.e. poor a bucket of the prepared tea on the affected soil.

Solanums is the next most cultivated family in most backyards and consists of
  • Chilli
  • Eggplant
  • Goji berry
  • Potato
  • Sweet peppers
  • Tamarillo
  • Tomatillo
  • Tomato

The soil based pathogen that affects this family is potato blight. While this blight mainly affects potatoes, growing any member of its family repeatedly in the same soil without a four year rotation gap may lead to pathogen build up to problem levels.
For more detailed info on how to avoid and recognise potato blight follow this link.

Below is a image I derived from analysing ABC gardening website

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