Saturday, 22 August 2015

Importance of Crop Rotation

If you have a veggie garden, chances are you are growing your favourite veggies year after year. By not rotating veggies (and their close relatives) you are running the risk of depleting the specific nutrients required for each type of vegetable and you are more likely to experience an increase in pests and diseases. A classic example is all Brassica crops (kale, cabbage, broccoli etc) are real nitrogen guzzlers so for good crop rotation it is wise to follow these crops with nitrogen enriching crops or green manure crops.

This large garden in Nana Glen
practices excellent crop rotation.
While the family Solanaceae (potato, eggplant etc) are quite prone to attack by nematodes there are other crops who are not, (beans and peas) so these are best grown following a Solanaceae crop. By rotating crops from one bed to another, you avoid a continuous build up of nematodes in any one bed. Vegetable crops should be rotated according to their family groupings. It is important to know what vegetable belongs to which family group, see the family groups listed:

  • Amaryllidaceae - Garlic, Leeks, Onions
  • Asteraceae - Chicory, Endive, Lettuce
  • Brassicaceae - broccoli, Brussel sprouts, Cabbage, Cauliflower, Kohlrabi, Radish, Rocket, Swede, Turnip
  • Curcurbitaceae - Cucumber, Melon, Pumpkin, Rockmelon, Squash, Watermelon, Zucchini
  • Fabaceae - all legume crops such as Peas and Beans
  • Solanaceae - Capsicum, Chilli, Eggplant, Potato, Tomato

The following layouts are based on two major rotations per year - namely Winter (April - September); and Summer planting (October - March). This timetable works well for the Coffs Coast allowing for progressive planting and harvesting as well as allowing time for crops to mature for seed saving purposes if you are interested in that. A six bed rotation is ideal for our warm climate as it leaves room for a dedicated green manure bed as well as individual beds for peas/beans and brassica crops. Where space is limited this can be reduced to five beds by combining Apiaceae and Asteraceae crops in the one bed. 

Example of a Winter layout:
Bed 1: Beans, Peas 
Bed 2: Broccoli, Cabbage, Kohlrabi, Swede, Turniip
Bed 3: Green manure crop
Bed 4: Beetroot, Carrot, English spinach, Parsnip, Silverbeet, 
Bed 5: Chicory, Endive, Lettuce, Squash
Bed 6: Capsicum, Chilli, Eggplant, Potatoes, Tomatoes

Followed by a Summer rotation for the same vegetables or family group:
Bed 1: Capsicum, Chilli, Eggplant, Potatoes, Tomatoes
Bed 2: Corn, Snake Bean
Bed 3: Cucumber, Pumpkin, Zucchini
Bed 4: Green manure crop
Bed 5: Beetroot, Ceylon spinach, Silverbeet
Bed 6: Lettuce, Mizuna

In the scenario above the Solanaceous crops grown in bed six during the winter move to bed one during the summer. Beans and peas crown in bed one during winter, join corn in bed two, bed two moves to bed three etc etc. Some crops not suitable for summer planting like brassicas are replaced with more climatically suitable curcurbit species like cucumber, pumpkin and zucchini.

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