Crop Rotation

by Ann Barnes

It’s a beautiful early August day in Durham. To beat the heat, I am making a list of fall crops I want to grow and deciding where in the garden each will be planted. Earlier this year, I drew and scanned a map of the garden, which I now use to record what is planted each season and to plan for future crop rotation.

 

Portion of garden map, with permanent planting of strawberries labeled.

Portion of garden map, with permanent planting of strawberries labeled.

Although planning your garden ahead and rotating your crops may seem like one of those extra steps you’d like to skip, there are some good reasons why you shouldn’t.

  1. Crop rotation helps keep populations of insect pests and disease causing microorganisms (pathogens) under control. Pathogens and destructive insects tend to prefer certain plant families. Many insects and disease organisms overwinter in the ground or on dead plant material. If the same plant – or a plant from the same family – is planted in one spot year after year, populations of pests will increase over time. Problems that might have been a nuisance can become severe enough to destroy a whole crop. Rotating crops makes it more difficult for pests to build up large populations.
  2. Different types of crops have different nutritional requirements. Some plants, like tomatoes, are heavy feeders – they take more nutrients from the soil. Root vegetables such as carrots are light feeders. Planting crops with the same nutritional requirements in the same spot for too long can decrease soil quality.

For crop rotation to be effective, don’t plant crops from one plant family in the same part of your garden more often than once every three years. This is where drawing and labeling a map of your garden each season comes in handy. Below are some commonly grown crops and their plant families (from http://watauga.ces.ncsu.edu/files/library/95/crop%20rotation%20factsheet.pdf).

Sunflower family lettuces, sunflowers
Goosefoot family beets, spinach, chard, quinoa
Mustard family mustard greens, rutabaga, kale, broccoli, cabbage, cauliflower, turnip, radish, watercress
Onion family garlic, shallots, leeks, onions, chives
Gourd family melons, squashes, gourds
Pea family peas, beans, jicama, peanuts
Nightshade family peppers, tomatoes, eggplant, potato
Carrot family celery, dill, chervil, fennel, carrot, parsnip, parsley
Grass family corn

Note that not all these plants should be planted now. See the following for planting times:
http://content.ces.ncsu.edu/central-north-carolina-planting-calendar-for-annual-vegetables-fruits-and-herbs.pdf

A sample crop rotation is included in this article: http://extension.psu.edu/pests/ipm/pestproblemsolver/house/home-garden/soil-plant-health/crop-rotation

The Getting Dirty Radio Show http://gettingdirtyradioshow.org/2015/07/31/a-second-season-sowing/ has an excellent post and recording about planting in August, including how to calculate a planting date based on information on seed packages.

Want to read more?
http://currituck.ces.ncsu.edu/2012/05/vegetable-crop-rotation/

http://watauga.ces.ncsu.edu/files/library/95/crop%20rotation%20factsheet.pdf

http://blogs.extension.org/mastergardener/2014/07/15/escape-the-heat-by-thinking-fall-gardening/

 

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