It’s true that modern farms are the most efficient and environmentally friendly they’ve ever been. There are many practices farmers have adopted that contribute to this.
One of these strategies is crop rotation, a carefully orchestrated plan that ensures farmers grow a diverse range of crops. This involves growing different plant species in a specific sequence, planting one type of crop one year, a different one the next, and so on. By following this practice, farmers can minimize the risk of pests and diseases, and maximize the amount of food they can grow.
On the Canadian prairies, a typical crop rotation involves cereals (wheat, barley, oats), oilseeds (canola, flax, mustard, sunflowers), and legumes (field peas, beans, lentils, chickpeas). Crop rotations are usually based on a 3-year, 4-year or 5-year cycle. For example, one year a farmer might grow canola, the next year wheat, the following year field peas, and then another cereal crop such as barley or oats.
Oilseed – Cereal – Legume – Cereal – Oilseed – Cereal – Legume – Cereal – and so on.
It’s not just grain farmers that use crop rotation. Vegetable farmers also rotate their crops, alternating between different families of vegetables, or alternating vegetable crops with cereal crops such as corn, or crops grown for animal feed like alfalfa or clover. And if you’re a gardener, you probably change the location of where you plant different types of vegetables from year to year. That’s crop rotation too!
Loads of benefits
The scientific study of different crop rotations has completely changed how farmers grow crops. In fact, rotating crops is one of the most important strategies for improving plant productivity. Crop rotations contribute to healthy crops by:
- Controlling pests AND creating conditions for good bugs to thrive. Since many insects and diseases target specific varieties of plant, not growing the same crop two years in a row reduces the ability of these pests to reproduce and spread. This natural method of pest protection means farmers don’t have to use as much pesticide, or any at all. Rotating crops also attracts beneficial insects like lady bugs and specific types of mites that feed on undesirable insects. Both can help control plant-damaging insects like aphids without the use of pesticides.
- Creating healthy soil. Farmers are able to grow healthy crops by managing the soil. Because different crops require different types and amounts of nutrients, crop rotations ensure no single nutrient in the soil is depleted, which contributes to keeping the soil fertile. Farmers plan their crop rotations carefully, testing the nutrients in their fields and selecting crops that will maximize the nutrients that are used from and returned to the soil.
- Reducing greenhouse gas emissions. Healthy crops capture carbon dioxide from the atmosphere and store it in the soil as carbon in the form of soil organic matter. Legumes like peas, lentils, beans, chickpeas or alfalfa are essential to a crop rotation because they capture and store atmospheric nitrogen – an important soil nutrient that creates healthier soil capable of sequestering more soil carbon in a faster way.
- Improving the biodiversity of farms. Different crops benefit different soil microbe species. Growing a range of crops will lead to a more diverse and healthy soil microbial community – and healthier soil.
How do farmers choose crops for their rotations?
It’s all about planning. There are multiple decisions that farmers make when choosing the right crops to use in their rotations. Here are a few:
- Crop residues – The plant pieces that remain after crops are harvested are called residue. Crop residues add organic matter to soil, which retains soil moisture, and improves movement of water throughout the soil as well as the structure of the soil layer. However, too much residue can increase the time it takes soil to warm up the following spring, which can delay seeding. Alternating crops with different amounts of residue ensures that residues don’t build up too much over the years.
- Nutrient requirements – Different crops have different nutrient requirements and will deplete–or add–different nutrients to the soil.
- Insect, disease and weed control – Controlling these pests is a continual challenge; however, crop rotation can control them. Different crops are not all susceptible to the same pests, so they will be less prevalent in following years.
- Marketability – Is there a market for a crop? There’s no point in a farmer selecting a crop type if there’s no place to sell it.
In summary, carefully planned crop rotations are an excellent tool to help farmers achieve many of their objectives, including improving soil fertility and crop yields, while keeping pests at bay. It allows them to carefully manage the risks involved in farming, all while using less fertilizer and pesticides and contributing to a healthier environment. It’s just one of the many ways that modern farming is contributing to sustainable food production.