“A good crop rotation is one with an adequate variety of crops grown so that any one type of crop is grown only once every 3 or 4 years,” explains Harry Brook, crop specialist at the Alberta Ag-Info Centre.
“A rotation like this can reduce pest costs, prolong the usefulness of pest control products and improve the bottom line. Limiting or shortening the rotation may provide short-term financial benefits but in the long-term, could severely limit future cropping options.”
One example that he uses is clubroot.
“It converts the canola root into a massive spore factory. It is spread through infected soils, but each year we see it found in more Alberta fields. Once you have clubroot, it is there for the long haul. These soil borne spores can remain viable in the soil for up to 20 years. If you have it, many counties will require the land be put on a 4 or 5 year canola-free crop rotation. Under short crop rotations - wheat then canola, for example - create ideal conditions to multiply spores and spread the disease.”
A variety of crop types can add to the health of the soil. He adds that pulses in a rotation improves soil health and reduces fertilizer costs.
“Peas, lentils and faba beans all capture nitrogen from the air and encourage beneficial bacteria and fungi that can benefit following crops. There is a nitrogen benefit left in the soil that extends up to 3 years after the pulse crop.”
Permanent forages in the crop rotation provide even more benefits, reducing the weed seeds present in the soil by depleting the weed seed bank.
“They also increase organic matter and are an excellent break for crop diseases and insect pests. A varied crop rotation can help diversify a farm operation, reducing financial risk. It also spreads out machinery use, making them more efficient.”
Moisture use efficiency also improves with a varied crop rotation, and he notes that canola, wheat, and peas all root to different depths and extract moisture and nutrients from different parts of the soil.
“A planned crop rotation can utilize soil moisture more efficiently. Permanent forages in rotation can also address soil problem such as soil salinity or acidity. Seeded in a field for 3 to 5 years, they are an excellent break from annual crops and add to the soil organic matter, which is your soil nutrient bank account. They can even reclaim some soils from salinity over time.”
“A diverse crop rotation also naturally varies the pesticides used and reduces the chance of resistance developing to pest control products,” he adds. “Conversely, a tight rotation can quickly develop weed, insect or disease problems, requiring greater expense to control the issue. In the case of clubroot of canola, the only answer is resistant varieties. Reliance on that genetic resistance has already caused it to break down.”
Connect with the Alberta Ag-Info Centre:
Hours: 8 am to 5 pm (open Monday to Friday, closed statutory holidays)
Toll free: 310-FARM (3276)
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