334 - Length of Crop Rotations
With the increase in sugarbeet acreage these past two years, the availability of suitable land may be limited in some areas. This could force more beet acreage into a short rotation cycle with beets planted every other year. While this may be profitable in the short term, a continuation of this practice could result in a buildup of soil borne diseases such as Aphanomyces and Rhizoctonia. Most sugarbeet varieties grown in the Red River Valley do not have resistance to these diseases so a longer interval between beet crops is the only practical long range solution. Research studies in Nebraska show that Rhizoctonia root rot was controlled in 4 year rotations but was quite severe in 2 year rotations.
Through the Grower Practices System, the Ag Department monitors crop rotation practices Company wide in an effort to evaluate current trends and possible future problems. Shown in the table are 10 year data on crop rotation length.
A majority of the beet acreage, about 60%, is grown in 3 and 4 year rotations and average about 1 ton per acre more than 2 year rotations (beets every other year). There is a trend toward increased yields with longer rotations, 5 years or more, that compares favorably with production from virgin land (no previous sugarbeet history).
Length of Rotation In Relation To Sugarbeet Yield & Quality
10 Year Average (1987-1996)*
|Years in Rotation||Years Between Beets||Acres||% Acres||Tons/Acre||% Sugar||% SLM|
* Data from representative fields (beets delivered on correct contracts).
Potential Nematode Problems With Canola In Sugarbeet Rotation
Increased interest in growing canola in the Red River Valley poses a potential nematode threat to sugarbeet. Both canola and sugarbeet are susceptible hosts for the sugarbeet nematode Heterodera schactii. The sugarbeet nematode is a microscopic eelworm that attacks sugarbeet roots causing stunted growth seriously affecting crop production. Nematodes multiply at about twice the rate on canola than they do on sugarbeet resulting in a build-up of nematode cysts in the soil. Although a soil survey in the Valley a few years ago did not reveal any sugarbeet nematode cysts, the potential for nematode increases with growing highly susceptible crops such as canola in rotation with sugarbeet.
The best way to prevent a build-up of nematode populations is to follow a good rotation where host crops are not grown too often. By growing non-host crops the nematode population declines because they cannot multiply on non-host crops. Suitable non-host crops in rotation with sugarbeet include all cereal grains, potatoes, sunflowers, flax, peas, beans, corn and fallow.
In Manitoba, where canola is grown more extensively, nematode cysts were identified in 1976 in one sugarbeet field. Since then nematode has been identified in all beet growing areas there. Levels found have been low and are kept under control through strict adherence to proper rotations. Manitoba’s sugarbeet contract now calls for a minimum 3 year rotation. It states: "The company will reject beets grown on land where beets or a crop susceptible to sugarbeet nematode were grown in any of the previous two years. Beets or other crops susceptible to sugarbeet nematode (canola and mustard) may not be grown in rotation more often than once in three years."
Sugarbeet and canola should not be grown on the same land unless you are prepared to grow them in proper rotation. The Crystal Ag Department recommends following the Manitoba rotation plan if both sugarbeet and canola are grown on the same land base. An example of a minimum 3 year rotation (2 years out of a host crop):