Have you ever considered how crop rotations can benefit your soil and increase your crop yield? In this article are the principles and benefits of crop rotation covered during the Afrimash webinar on April 27, 2022.
Meet the Facilitator: Sidney Okeke
Sidney Okeke is a Crop scientist and also the crop category manager at Afrimash Company Limited where he manages everything concerning crop farming for the company. He provides technical support to customers on crop-related issues. He is an agricultural entomologist and also a data analyst.
He obtained his first degree in Plant Health Management from Michael Okpara University of Agriculture, Umudike, after which he bagged an M.Sc. from the University of Ibadan in Agricultural Entomology. He is presently running his PhD programme in Agriculture at the University of Ibadan. He is a member of the Entomological Society of Nigeria and also the National Society for Plant Protection.
If you are looking to protect your soil and improve your crop harvests, read on on the general principles and benefits of crop rotation.
What is Crop Rotation?
Crop rotation is an age-long practice that has been in use for hundreds of years. It is a cropping technique that involves the intentional planting of different types of crops in different parts of the field and at different seasons in a sequential manner.
It involves the growing of a series of different types of crops in the same area across a sequence of growing seasons. The succession of crops to be grown is carefully designed to ensure soil nutrients are sustained, pest populations are controlled, weeds are suppressed and soil health is built.
Rotations are the changing of crops over both space and time. Well-planned rotation schedules benefit soil fertility, aid in pest management, and spread labour needs over time.
Factors to be Considered In Carrying Out Crop Rotation
Factors such as crop family, plant rooting depths and crop fertility needs should be considered when developing a crop rotation schedule.
There are some factors to be considered in carrying out crop rotation. Crop rotation is just alternating crops in the same piece of land to maintain the different aspects of the farm to maintain the soil texture and soil nutrients. Doing this helps to reduce pest infestation on the farm over time. So, one needs to consider such things as the family of the crop. What that means is this, some crops have specific host ranges.
For example, the Solanaceae (tomato, pepper, eggplant) have peculiar pests, such as the whitefly (Bemisia tabaci). Although it also cuts across some other crops. But if you plant something like Solanaceae crops on a piece of land, which is a shallow feeder, it will also be wise to follow it up with another crop in another family to ensure you don’t have the same pest build-up. We should bear in mind that most pests are host-specific. One of the main advantages of using crop rotation on our soil is to help ensure that we break the lifestyle of these pests.
The exact sequence of crops will vary depending on local circumstances, with the critical design element being an understanding of what each crop contributes and takes from the soil. For instance, nitrogen-depleting crops should precede nitrogen-fixing crops.
It means that it is necessary to understand the physiology of the crops to include in the rotation. Some crops are shallow feeders (e.g. Okra and Tomatoes), while some are deep feeders (Yam and cassava). It is, therefore, essential to know what strata of the soil the plant may be feeding.
The general idea is to have the crops sustain soil health themselves, rather than planting the same crop year in, year out and then repairing soil health through fertilizers, pesticides and herbicides.
When you practice crop rotation correctly, it reduces the dependence on fertilizers and pesticides. These pesticides can destroy the population of beneficial microorganisms.
When a farmer plants just one crop (monocropping) continuously on a piece of land, there is a big chance over time, a build-up of many pests and diseases that affect the crops. It may force the farmer to rely on pesticides which we all know are harmful in one way or the other to the crops. But when you practice crop rotation, because most pests are host-specific, they will never be able to survive on other crops the way they do on one.
For instance, the Aphids that affect cowpea and groundnut (Aphids castura), if you remove your cowpea and you plant your maize, it won’t be able to survive on the maize. So, the life cycle there is broken, as also the pest population. So, over time, that is the idea. When you remove that, you put something else to take nutrients from another soil level. Some crops feed deep in the soil, such as cassava. After that, it will be wise to put something else that feeds in another part of the soil. From the shallow part of the soil. That way, the nutrient and the pests disturbing the crops there would be maintained over time.
General Principles of Crop Rotations
For any program to be successful, it must undergo careful planning and execution. Farming activities are not left out in this light. One needs to follow some rotation. Some of the principles include but are not limited to:
1. Crops belonging to the same natural order (family) should not follow one another.
An example is to avoid crops such as Tomatoes, Pepper, Eggplant or Tobacco following each other in a sequence because they all belong to the same family, Solanaceae and as such, share similar pests. It is therefore advisable to follow such with crops belonging to a different order and family to help achieve the purpose.
2. The deep-rooted crop should be followed by a shallow-rooted crop and vice versa.
Deep-rooted crops such as cassava should be followed by shallow-rooted crops such as Okra. This ensures that while the cassava feeds from a deep part of the soil, the nutrients in the shallow part of the soil will still be available for the Okra to utilize when it is planted.
3. Exhaustive crops (e.g., cereals which take more nutrients from the soil and do not add anything to it) should be followed by restorative crops (e.g., legume crops which not only take nutrients from the soil but at the same time also add nutrients to the soil). It is important to include legumes in the rotation program because of the roles they play in soil fertility. Most legumes fix nitrogen into the soil and this enriches the soil and reduces the dependence on fertilizers. That way, it reduces the cost of production for the farmer.
4. Green manure preferably legume crops should be included in the rotation. Green legumes serve as cover crops and they also help prevent erosion while enriching the soil.
5. Long-duration crops should be followed by short-duration crops.
6. Broadleaved crops should be rotated by narrow-leaved crops. This ensures that crops with different physiologies are alternated.
7. Crops with taproot should be followed by crops with a fibrous root system. This helps in the proper and uniform use of soil nutrients from different depths of the soil.
8. Crops with minimum water requirements should be grown in periods of water deficiency.
9. After harvesting, you try as much as possible to leave the residues on the farm, so that they can decompose and provide nutrients to the soil against the next planting. It helps when they are ploughed back into the soil and they provide nutrients to the soil for the next crop to be planted.
10. It is very important to select crops that can address the issues of the land. The selection of crops should be problem-based, e.g. on sloppy lands, erosion-resistant crops (spreading types like legumes) should be incorporated into the plan.
Advantages of Crop Rotation
A well-designed crop rotation makes land both more productive and more environmentally sustainable. It improves the financial viability of a farm by increasing productivity whilst reducing chemical input costs. Some of the advantages of crop rotation are:
- Improved Soil Fertility and Structure
Crop rotation improves soil’s physical and chemical conditions and thus improves overall fertility. Nitrogen-fixing legumes such as soybeans and alfalfa in crop rotations fix atmospheric nitrogen into the soil through root nodules. This nitrogen is then available for subsequent crops.
Deep-rooted cover crops can draw up nutrients such as potassium and phosphorus from deep in the soil profile, making these nutrients available for subsequent shallow-rooted cash crops.
Growing crops like maize in a rotation can result in improved tilth and bulk density. When you plough the crop residue, the soil will be loose and have an excellent granular structure and tilth. These improved properties result from the soil’s protection from raindrops, the network of fine roots in the soil, and the formation of humus from decomposing plant roots.
- Disease Control
Crop rotation helps to control common root and stem diseases that affect crops. It is highly effective against diseases whose pathogens have a small host range. For such diseases, rotating a non-host crop immediately after a host crop prevents the pathogen from reproducing.
The pathogen inoculum, ordinarily preserved in crop debris, does not have the necessary conditions for its survival and the disease spread is controlled. For example, soybean cyst nematode populations can be cut in half by rotating soybean with wheat and corn.
In the absence of crop rotation, growing the same crop on a particular land year after year gives pathogens continued optimal conditions, and their population will increase rapidly.
- Pest Control
Because most pests are host-specific, Crop rotation can be used as a tool to manage that insect which has a narrow range of crops to feed on. For instance, corn rootworms can be managed effectively with crop rotation. These insects lay eggs in the corn fields they live on, and emerge to damage subsequent crops. Rotating a non-host crop immediately after a corn crop means that emerging larvae starve due to scarcity of food.
- Weed Control
Including cover crops into crop rotation systems provides greater competition to the weeds for their basic needs such as nutrients, space and light. Cover crops ultimately crowd out the weeds, slowing down weed growth and proliferation for a reduced weed population in subsequent crops. A good example of cover crops is the mucuna species.
- Increased Soil Organic Matter
Crop rotation will add more crop residues, green manures and other plant debris to the soil. Crop rotation also requires less intensive tillage, which means that soil organic matter does not degrade as quickly. Increased soil organic matter improves soil infiltration and water holding capacity, which enables water to be absorbed into the soil. Furthermore, increased soil organic matter improves overall soil structure and the chemical and biological properties of the soil.
- Erosion Control
Also included in the benefits of crop rotation is that it helps control the erosion of soil from water and wind by improving the soil structure and reducing the amount of soil that is exposed to water and wind. Crop rotation also supports reduced or no-till farming, which ensures even better protection against erosion.
To this end, Cover crops are effective in reducing raindrop impact, reducing sediment detachment and transport, slowing surface runoff, and so reducing soil loss to erosion.
- Improved Biodiversity
Crop rotation helps improve soil biodiversity by changing crop residue and rooting patterns. Different crops benefit different species, and so a range of crops will lead to a more diverse and healthy soil microbial community. The beneficial biodiversity of fauna in the soil is maintained by the proper execution of crop rotation.
- Increased Yield
Crop rotation that’s carefully planned can lead to increased yield and also reduced cost of production. If maize for instance is planted after a nitrogen-fixing crop, it tends to benefit from the nitrogen already fixed by the legume. Thus, there would be an increase in yield.
Question: Can you give examples of exhausting crops? Another leguminous crop apart from beans?
Response: Exhaustive crops as used above refers to crops that take nutrients from the soil but have nothing to give back in return. examples are cereals such as maize, millet etc. In contrast to Legumes that use soil nutrients and also fix nitrogen that enriches the soil and increases the Nitrogenous content of the soil.
Apart from beans, one can incorporate Soybean and even groundnuts are examples of legumes that have good nitrogen-fixing abilities.
Question: I’m a little bit confused. Are you saying we should plant different crops at the same time on a particular plot of land? For example, can you plant cassava and corn at the same time?
Response: Personally, I have done this on some occasions and harvested reasonable yields on both crops. Because both crops have different physiology and feeding requirements, they can be combined in a field at the same time.
Question: In point 4, you mentioned green manure and green legumes. Are they the same or different?
Response: Well, the terms Green manure and green legumes are sometimes used interchangeably. Green manures refer to those crops that can help enrich the soil. Mucuna species are good examples of green manures.
Question: I’d like you to please recommend a natural insecticide that can be used against Aphids. If you know the process of Making it, you can kindly say it as well. Thanks.
Response: A natural insecticide: I have personally worked with Neem Azadirachta indica and Hyptis suaveolens for the control of insect pests. There are documented reports of them being effective in insect control. There are various ways of utilizing them, and the process is long. In the lab, you may have to use a soxhlet apparatus for extraction and a rotary evaporator to condense the oil before dilution.
Question: What pest control can I use for a combination of Yam and corn farm.
Response: The term pest control is a little vague. Because we know pests range from Insects to weeds, pathogens, rodents etc. It would be difficult to know the exact pest you wish to control.
Question: Can I get improved seeds and seedlings from Afrimash?
Response: Yes, you definitely can
Question: Do you also give room for consultations ( Based on Crop farming)
Response: At Afrimash company limited, all areas of farming are handled by professionals. I personally provide technical support for all areas of crop farming to our customers on behalf of the company.
Question: Can we get more like a chat for a crop rotation cycle?
Response: This is very possible, but what I listed here are the principles. In a rotation, the cycle would depend on many factors, such as location, season, the farmer’s needs, available market etc. That’s why one can try to understand the principles and you can consult professionals with your choice of crops for them to guide you through.
Crop rotation is very important in agriculture. With a little planning and preparation, you’ll be able to plan out crop rotations that will bring the most benefits to your farm. Have you gotten something helpful out of this guide on the principles and benefits of crop rotation? Let us know your thoughts in the comment section.