2 Big Reasons to Implement Crop Rotation in Your Next Growing Season
Crop rotation is the practice of growing different crops in a sequence on the same field and it has been used as an important tool to improve farming since the early days of agriculture. In this practice, each crop serves a different purpose in the order of rotation. The crops are categorized into two main groups: Feeder crops and cover crops. Feeder crops deplete the soil nutrients, whereas cover crops are used to restore the soil, green manure, and prevention of erosion.
The main benefits of crop rotation are disease and pest management and preservation and restoration of soil health. Though, there are additional benefits such as reduced reliance on chemicals and cattle grazing that will not be discussed in this scope.
Chenopodiaceae (e.g. spinach, beetroot)
Brassicas (e.g. broccoli, cabbage)
Cucurbits (e.g. cucumber, melon)
Solanaceae (e.g. tomato, potato)
Alliums (e.g. onion, leek)
Legumes (e.g. alfalfa, beans)
Grasses (e.g. sorghum, oats)
Managing Pests and Diseases with Crop Rotation
Pests and diseases are one of the biggest challenges to growers worldwide. The good news is that crop rotation can help combat pests and diseases by interrupting life cycles and altering pest habitats.
The spread of pests and diseases can be inhibited by understanding their life cycle. Fungi, bacteria, insects, nematodes, and even viruses have specific hosts that can be removed and habitats that can be made less favorable to them. This can help disrupt and reduce the population of pests and diseases.
For example, if a potato field has a Colorado Potato Beetle infestation, alfalfa can be planted in the following season to reduce pest pressure. What would planting alfalfa in this case achieve? Well, during the growing phase, the beetle will lay its eggs in the field. The eggs would hatch in alfalfa plants, which are not viable hosts for the beetle. This means that the larvae population will be greatly reduced because of its lack of mobility (in the larvae stage the pest doesn’t have wings). By altering the beetle’s habitat, and interrupting its life cycle, prevention of a buildup of the beetle’s population for the next planting season is achieved.
If the grower were to grow potatoes in neighboring fields, it would reduce the effectiveness of using alfalfa for crop rotation because the potatoes would act as a temporary host for the beetle. Beetles can migrate back to the main field the following season when the potato crop is planted again.
While the alfalfa is grown in the field as a cover crop, weeds from the solanaceous family (such as nightshade) may host the beetle. Thus, weeds can also function as potential transitional hosts and act as temporary hosts for the beetle. Such challenges among others can hinder the effectiveness of crop rotation.
Growers can achieve higher yields by having a good understanding of the biology of pests and diseases. Does the pest or disease have a wide or short range of hosts? How long can the pest or disease survive without a host? How mobile is it? These and other questions need to be addressed when planning crop rotation for pest and disease management. Additionally, by relying less on conventional chemicals for pest management, there is less chance of the pests and diseases developing resistance which leads to a higher success rate of eradicating the problem.
Preserving and Building Soil Quality
While crop rotation implications on plant protection is an important consideration for its own sake, growers need to pay attention to soil quality. Years and years of intensive single-crop farming can exhaust the soil, deplete its nutrients and damage the microorganism ecology. This can reduce yields, increase the need for fertilizers, and increase soil pathogens that damage the plants. How can crop rotation help build good soil health?
Some crops are known to be beneficial for soil health; these are known as cover crops. Cover crops promote soil health and structure, return nutrients to the soil, and contribute to the soil ecology.
Potato is an example of an exhaustive crop, which means that soil’s nutrients can be depleted after growing potatoes consecutively. Growers can prevent exhaustive crops from depleting soil by planting cover crops. In this case a legume such as alfalfa.
Why legumes? Legumes are known to be restorative crops. Legumes have symbiotic relations with bacteria in their root system that capture atmospheric nitrogen and return it to the soil in a form that is available to the plant. Legumes also have a deep taproot which is used to recycle nutrients that are deeper in the ground.
Grasses can be used as cover crops as well. Grasses have wide fibrous root systems that secrete substances into the soil and promote soil aggregation. This process stabilizes the soil and improves aeration. Their roots also decompose slowly and act as a source of slow-releasing nutrition.
What makes cover crops even more interesting is the fact that they can be used as green manure. At the end of the season cover crops can be cut up or left to decompose in the soil. Doing so adds rich organic substance to the soil and promotes soil health. However, the usage of green manure should be planned carefully as the decomposing plant material may be a source of inoculation and the spread of pathogens.
Using legumes, grass or even leaving the soil fallow for some period can greatly benefit soil health. It can return nutrients, promote soil microorganisms, and better the soil structure.
The nitrogen cycle
Nitrogen fixers from the pea family (peas, beans, and clover) increase the level of nitrogen in the soil. Nitrogen is the most abundant in the atmosphere, but in its atmospheric form, it cannot be utilized by plants. To make it available to plants, we need the help of bacteria that have the ability to absorb atmospheric nitrogen and output ammonia. Other bacteria can consume ammonia and create nitrite and nitrate. These three forms of nitrogen are available to plants. Symbiotic connections of fungi with the root system allow plants to absorb these molecules even if they are not nearby.
Nitrogen gets depleted from the soil by volatilization, a process in which gas escapes the soil and returns to the atmosphere. In addition, nitrogen in different forms can be washed away by water (leaching). Moreover, there are other bacteria that, in anaerobic conditions, consume nitrate and release nitrogen back into the atmosphere (denitrification).
The nitrogen-fixing plants create an ideal habitat for the bacteria that accomplish the nitrogen-fixing process described above. After the plant dies, the bacteria are released into the soil, increasing the bacteria population in an accumulative way.
The environmental benefit is due to the fact that fixed nitrogen is considerably less prone to washing effects and volatilization. Nitrogen from synthetic fertilizers is not attached to biological organisms and can be washed into water bodies such as rivers and change the ecological balance. In addition, it more easily escapes to the atmosphere as nitrous oxide, a contributor to climate change.
Planning out a crop rotation
Poor yield, heavy fertilizer reliance, and high pest and disease pressure should incentivize growers to make plans for crop rotation.
Planning of the crop rotation can be divided into several steps:
- Deciding which cover crops are available to be used based on location and climate, local market trends, and the season of the available field.
- Deciding when to plant the cover crops. Ask yourself how often you can afford to rotate and what type of rotation. Are you going to plant only in the off-season, or have several consecutive seasons of cover crops?
- Deciding which cover crops to use: legumes or grasses. Both legumes and grass have relatively low nutrient demands and can be used as green manure. Other considerations that should be taken into account include their main benefits:
- Important in the process of atmospheric nitrogen(N) capturing.
- Recycles nutrients from deeper soil.
- Promotes soil aggregation and aeration.
- Acts as a source for the slow release of organic material.
The root systems of cover crops hold the soil together and stabilize its structure which prevents strong rain and storms from causing soil erosion. Cover crops promote a diverse field that can combat weeds and might even suppress weed growth. In addition, rotating with a crop allows for easy weed control and gives growers an opportunity to reduce the build-up of weeds.
When used correctly, crop rotation can be an effective and powerful tool to add to crop management. Its benefits can be wide and long-lasting for managing pests and diseases by interrupting life cycles and altering habitats, preserving and promoting soil health and stability, and enriching the microorganism ecology of the soil.
We can help growers to be better, greener, and more effective.
- Our platform helps growers keep records of the crops in their fields.
- Our database can help growers plan a crop rotation by providing a historical account of pests and diseases in the region.
- Our resource library provides detailed information on the life cycle and range of hosts for pests and diseases in accordance with specific crops and locations.
- Our system generates end-of-season crop cover recommendations.
We are looking forward to seeing you apply this information to build a smart, effective crop rotation in your field. In the meantime, as always, we wish you an abundant harvest.