Planning a Crop Rotation

Now that summer is starting and the crops are well established, have you started thinking about next year? Do you have a planned rotation for each field? Does this include cover crops whenever possible? Organic farmers know that a good crop rotation is the basis of a good cropping system to allow them to maintain good pest control.

Disease

Good crop rotations help to develop healthy soils and are better able to suppress pests and improve the health of the crops. For example, there are approximately 50 diseases of beans (Phaseolis spp.). Crop rotation helps to eliminate about 33 of them, including bacteria and nematodes and nearly all fungi diseases. One of ways this works is that plant pathogen propagules have a lifetime in the soil, and a crop rotation that excludes host crops starves them out.

Diverse crop rotations lead to more diversity in the soil. Cover and rotation crops shift the composition of the non-pathogenic microbial community to be more suppressive to diseases. Many studies have shown Brassica cover crops to suppress diseases. It is felt that the glucosinolates, which break down to isothiocyanates, contribute to this, but there are also other compounds involved as well. Oat cover crops have also been shown to suppress root rot in peas.

Insects

Similarly, insects are suppressed by good rotations. When we grew a lot of continuous corn 25 years ago, even second-year corn needed a corn rootworm insecticide. During the past decade our use of corn rootworm control has declined to a fraction of usage in the 1980’s due to the fact that we now rarely grow corn-after-corn.

Weeds

Crops can be planted in either spring or fall, which alters their abilities to compete with weeds. Related tillage activities can also kill germinating weed flushes in spring or fall. Cereals crops are planted in narrower rows which help them canopy and out-compete weeds. Forages crops are cut several times each summer which is an excellent way to suppress many perennial weeds.

Spread The Workload

A good crop rotation also spreads out the workload, which is a labour saving in the overall operation of the farm. Improving your crop rotation may also let you increase the size of your farm within your existing resources of labour and equipment.

Having a good crop rotation will make you money, both by increasing yield and by decreasing costs. Crop rotation takes planning to make sure it meets the needs of the farm and the flexibility to allow you to take advantage of market changes.

Action: Plan your cover crops and crop rotation for 2007 and 2008 now!

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