Crop rotation has long been considered an important farm practice.
Crop rotation, or the planned sequence of specific crops in a field, can require additional planning and management for farmers. However, the benefits of good crop rotation are numerous and include reduced soil erosion and improved soil water management, soil tilth, and fertility.
Crop rotation can also reduce pest issues and reliance on pesticides. Rotations also allow farmers to spread their workload and better utilise labour and machinery resources. The risk from weather related incidents can also be reduced with a good crop rotation.
There are a number of basic principles to consider when determining a crop rotation. One basic principle is crop water use. Crops such as sunflowers and corn are considered high water use and can draw soil water to very low levels at harvest.
The success of crops planted after a high-water use crop will be determined in part by weather and the amount of precipitation received, caught, and infiltrated between harvest of the high-water-use crop and seeding and/or moisture sensitive periods of the succeeding crop.
In all cropping systems, water use must match water availability. If the system is not sufficiently intense, problems such as waterlogging, saline seep formation, nutrient loss, trafficability problems, etc. are common. If the system is too intense, poor yields due to water stress or stand establishment problems are likely.
Another determining factor in crop rotation decisions are pests. Crop rotation has long been advocated as an excellent way to break the cycle of disease, insects and weeds. It is commonly accepted that yields of crops grown in rotations are 10% (or more) higher than yields of crops grown in a monoculture.
This yield benefit is sometimes referred to as the rotation effect. The common thought is that this benefit is the result of a number of factors working together, among those, is a reduction in disease and other pest issues.
Crop rotations will be more successful if they include three or four crop types (cool-season grass, cool-season broadleaf, warm season grass and warm-season broadleaf). Also, rotations that are not consistent in terms of either interval or sequence provide the best protection against shifts and biotype resistance.
In other words, rotations such as wheat-canola or wheat-canola-wheat-pea are consistent in both interval and sequence.
Wheat always occurs in alternate years and always follows a cool-season broadleaf. Rotations such as spring wheat-winter wheat-pea-corn-millet-sunflower are not consistent in either interval or sequence. Rotations should have crop type to crop type intervals of a minimum of two years somewhere in the rotation.
There are a number of common plant diseases where the recommended best control method is listed as crop rotation. In these circumstances, crop rotation can lead to a healthier, more resilient crop by reducing and preventing the transmission of disease.
However, there are a few situations where the cycle of plant disease can be aggravated by crop rotation. The one that comes to mind is wheat after corn or sorghum.
Another important consideration for farmers in determining crop rotations is workload. Equipment and labour can cover more acres with crops that are seeded, sprayed and harvested at different times throughout the growing season.
Overall crop rotation is known to be a beneficial management tool. However, each farm will have to determine its own specific rotation dependent on soil, climate, equipment and human resources.
The idea of crop rotation – growing different crops on the same land each year – can be difficult to understand. After all, if you’ve been growing maize and only just managing to feed your family, why reduce the amount of maize you plant (which is what crop rotation requires) and plant something else? But here’s the secret: crop rotation will increase your maize yield and give you a surplus to sell.
Crop rotation has the following benefits:
• It makes your soil more fertile, as legumes such as beans and groundnuts fix nitrogen in the soil.
• You use less chemical fertiliser because the nitrogen is fixed naturally in the soil.
• It helps to control weeds, diseases and pests by breaking their life cycles.
• It reduces the risk of crop failure in case of drought or disease.