Chances are that you probably live closer to a farm than you might realize. If you pay close attention to farms from year to year, you'll notice that a field that was once filled with corn might be filled with soybeans the following year. What's going on here?
Is a fickle farmer changing his mind? Does he get tired of corn? Or is there a good reason for switching crops in fields from time to time? Actually, there's a very good — and scientific — reason for farmers to plant different crops in a field from year to year. It's a process known as crop rotation , and it's actually been around a long, long time.
Crop rotation refers to the practice of growing different types of crops or none at all in the same area over a sequence of seasons. Historians believe farmers in the Middle East practiced crop rotation as early as 6, B. So what's wrong with planting the same crop in the same field season after season? As farmers thousands of years ago learned, several problems begin to creep up when you don't rotate crops. All of these problems can lead to decreased yields over the course of several years.
This is because the same type of crop planted repeatedly in the same area keeps draining the land of the same nutrients needed for that plant's growth. Second, certain pests can reach levels that are hard to control when they learn to make a home near a field that always has the same type of crop.
Finally, land can be more susceptible to the forces of erosion if the same type of crop is planted repeatedly season after season. Crop rotation helps mitigate each of these effects. Different types of plants require different types of nutrients from the soil. Changing crops routinely allows the land to remain fertile , since not all of the same nutrients are being used each season. For example, planting a legume , such as soybeans, helps to replenish necessary nitrogen in the soil.
In the past, not planting anything also called leaving the field fallow allowed the land to rest and replenish its nutrients. Some modern farmers will occasionally allow fields to lie fallow to rest, but crop rotation has helped to increase productivity by replacing fallow periods with growing different crops that replenish soil nutrients.
Crop rotation also helps to battle against the forces of erosion. Rotating crops helps to improve soil stability by alternating between crops with deep roots and those with shallow roots. Pests are also deterred by eliminating their food source on a regular basis. Today, exactly how crops are rotated depends upon many factors, including the type of soil , the climate, precipitation , and the markets for various crops.
Some modern farmers may rotate corn and soybeans in a single field on alternate years. Other farmers may rotate six or more crops in a field over multiple years. We hope you enjoyed learning more about the science of farming today! Check out the following activities with a friend or family member to learn even more!
Hi Tateum--we suggest a Wonder Journey--hit up your library or the Internet to find out more about this topic. If you are trying to cite the article, you can use Wonderopolis as the author and the date accessed for a digital work. It sounds like you are a very hard worker, alex! The following paragraph will help you learn more about the benefits of crop rotation:. I knew what the crop rotation was, but didn't know why we used it. Wonderopolis had just the article I needed. Yes, it's very important - you're right!
This is an interesting method that many people probably don't understand the importance of. Glad you do! Dinner would be pretty boring, that's for sure. It also seems like that could have serious effects on the ecosystem, especially if the crop ran into trouble. Good question! Do a little more digging and see what you come up with!
Very cool, Tim! We are so glad this was a great resource for you. Great question, vaz! The following is how you would cite the Wonder of the Day. You may use Wonderopolis as the author and since we do not list the publish date, you can use the date you accessed the article for information. If that was today, then use today's date for your citation.
Great question, Vazul! We didn't create the video, so we couldn't find an explanation. We're glad you learned something new from this Wonder of the Day! Good luck with your mini-farm!! We really enjoyed your comment, Audrey! We bet it's a lot of fun to pick berries with your family - what a tasty activity to do together!
Thanks for hanging out with us in Wonderopolis! Thank you for asking, Aiden! We have a hard time picking just one, but there is one that's very near to our hearts - our very first Wonder! Have you read it? That's a great question, Max! Depending on the region you live in, there may be crops that can grow in the winter. Estimates of total nitrogen in a soil with 3 percent organic matter range from 2, to 4, pounds per acre; estimates of phosphorus range from to pounds per acre.
Soil microorganisms release these nutrients when they consume organic matter and subsequently die. The rate of this nutrient release is affected by the availability of carbon sources energy for the soil microbes , soil temperature, soil moisture, tillage, types and numbers of soil organisms, and quality of the soil organic matter. This active fraction is replenished primarily by additions of organic matter cover crops, crop residues, manures, compost. Soil organisms, which make up another 10—20 percent of soil organic matter, decompose this active organic matter.
Upon death, these organisms release their nutrients to plants. The remaining soil organic matter is humus. The humus is more slowly digested by soil organisms and therefore is not a large source of available nutrients.
Humus is very important, however, because it provides cation exchange sites, which hold nutrients in the soil and thus maintain their availability to plants. Organic matter amendments to soil decompose at different rates, and this affects how quickly nutrients become available to crops. Several factors affect the rate of decomposition of organic amendments, including the carbon-to-nitrogen ratio of the amendment, soil type, temperature and moisture conditions, and the crop being grown.
Green manures, which are part of the more active organic matter fraction, decompose readily, liberating nutrients relatively quickly. Composts have more stable, humic organic matter, and decompose more slowly. As a result, most composts release nutrients to crops more slowly than green manures. Organic matter decomposition is enhanced in the area immediately around roots the rhizosphere. Roots release organic compounds, such as carbohydrates, amino acids, and vitamins, into the soil, stimulating growth of microorganisms in this zone.
Many of these organisms decompose organic matter, resulting in nutrient release to the crop. Very little research has been done to determine which plant varieties or species best support these nutrient-releasing microorganisms.
In the future, such information may help identify crop varieties well adapted to organic systems. When cover crops are regularly part of a rotation, their residues increase soil organic matter.
The organic matter feeds the growth of microbes, which increases the release of N as they die and decompose. Thus, integrating cover crops into a crop rotation at specific points can help enhance nutrient cycling and conservation. Legumes may be present in a rotation as a harvested crop for example, alfalfa or as a green manure for example, vetch or clover. Legumes are of special interest in organic crop rotations because of their ability to add nitrogen to the system.
Specialized bacteria R hizobium spp. The amount of N fixed by this association between bacteria and legumes varies with plant species and variety, soil type, climate, crop management, and length of time the crop is grown. When used strategically in a rotation, legumes provide N to the subsequent crop.
The amount of N that a legume crop contributes to following crops depends on the amount of N fixed, the maturity of the legume when it is killed or incorporated into the soil, whether the entire plant or only the root system remains in the field, and the environmental conditions that govern the rate of decomposition.
As a result, estimates of the amount of N contributions by legumes to subsequent crops range from 50 to over pounds per acre see Appendix 1.
Winter-hardy grains and grasses have extensive root systems that are more efficient than legumes at scavenging soil nitrates in the fall, thereby reducing late fall and winter leaching of nitrogen In the northeastern US, small grains rye and wheat are the most common winter-hardy cover crops used by vegetable growers, since harvests of cash crops often extend into late summer and fall.
Once incorporated in the following spring, these cover crops will release captured N and other nutrients to subsequent crops, but at a slower rate than from legume cover crops because of the slower decomposition of grain residues. In some cases, such as when heavy crop or cover crop residues with high carbon-to-nitrogen ratios or higher are tilled into the soil, soil N may become unavailable to plants immobilized in the short run because it is taken up by soil microorganisms as they feed on the carbon-rich residues.
Seeding a legume cover crop with small grains for example, hairy vetch with cereal rye can reduce N immobilization by providing additional N to microorganisms during decomposition of residues. Alternatively, delaying the planting of a cash crop for about two weeks after incorporation of residues generally allows sufficient time for the cycling of N through microorganisms and then back into the soil.
Incorporating nonlegume cover crops while they are still young and leafy also reduces problems with N immobilization. One important consideration when using overwintering cover crops is their potential to deplete soil water. Although cover crops can improve water infiltration and soil water-holding capacity, the short-term depletion of soil water in the early spring can reduce yields of subsequent cash crops in dry springs.
In this situation, cover crops may need to be incorporated early to conserve soil water, or irrigation may be required.
The opposite is also true—cover crops can help dry up wet fields in the spring. The amount of soil N captured is related to the N that is available, the time of planting, and the total growth of the cover crop prior to being killed.
Researchers observed that B r a ssi c a cover crops grew more in the fall and, as a result, captured more N than an oat cover crop Watch the complete interview with Craig explaining canola rotation impact on plants and soil biology in Western Canada: In addition, discover in this article why crop rotation is important, and why adding the beneficial mycorrhizal inoculant is one of the key solutions! Increase Soil Fertility Soil is fertile when it provides all the favorable conditions for plant growth.
Improve Soil Structure A good soil structure arrangement of soil particles in various aggregates differing in shape, size, stability, and degree of adhesion to one another is important for water and air infiltration and erosion control. Prevent Soil Erosion Adding mycorrhizae will clearly improve soil quality by building a better soil structure. Increase Crop Yields The combined effect of the four reasons above tend to show that crops will see an increase in yield with crop rotation, and why it is considered good agricultural practice.
Growing canola? Have a look at the Canola Council tips and details to help you plan your canola rotation. See also. The passion of innovation. The will to make it better. Subscribe to our newsletter! You are now subscribed to our newsletter. Who are you? Grower Retailer Distributor Other.
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