Crop Rotation 101

The development of agriculture represented a monumental shift in the evolution of humans, but as we’ve perfected many different techniques to yield the things we want and need from the earth, the science of ecology has evolved right alongside us.

As humans have come to discover—or, in some cases, rediscover—the nuances of earth’s natural cycles, we’ve developed ever-more sophisticated ways to work with what Mother Nature already provides to help grow our food, including through the concept of crop rotation.

What Is Crop Rotation?

The idea of crop rotation is right in the name: Switching out the crops being grown after each harvest or so.

It may sound simple, but it stands in stark contrast to the way things are increasingly being done—through a system called monocropping, which describes one field being used to grow the same crops, over and over again.

As the market has evolved to create more demand for certain produce—like corn, which can be used for anything from biofuel to livestock feed—farmers have found themselves bending to these demands, but the process is the most demanding of all on the earth itself.

That’s because in order to grow the same crop, the soil must yield the same types of nutrients, over and over again. Eventually, monocropping results in draining the soil of these particular nutrients, until the earth either becomes unusable or a substantial amount of synthetic fertilizers and other chemicals must be used to reestablish nutrient levels.

Crop rotation, on the other hand, uses a few natural tricks to help keep things running. If corn, for example, will take certain minerals out of the ground, a farmer will follow up that harvest with a crop that adds those nutrients back into the mix as it grows.

And though we’re discovering more efficient ways to utilize this concept all the time, the idea of crop rotation itself has a long history in human agriculture, dating back nearly 6,000 years.

How Does Crop Rotation Work?

Indeed, many older cultures were the ones to first develop the mechanics of crop rotation, which typically utilizes anywhere from two to four fields to complete the cycle.

Of course, farmers can extrapolate these basic rhythms out to any number of fields, but some of the most basic crop rotation patterns look like:

Two-Field Systems

One of the most simple crop rotation patterns, this system is also one of the oldest.

Essentially, a farmer will manage two fields. One field, he or she will grow crops in, while the other is allowed to remain dormant. Then, after the season is over, the farmer will switch the two fields.

The concept lets the earth intermittently rest between growing sprees, resulting in a longer-lasting natural vibrancy.

Three-Field Systems

First developed in the Middle Ages, this type of crop rotation system was likely originally designed to help farmers get more out of the same amount of land while still allowing some of it to rest.

For example, if a farmer owned 600 acres of land, a two-field rotation would only let them harvest 300 acres at a time, while a three-field system would give them 400 usable acres every year.

The system also keeps intact the concept of maintaining one fallow field, to keep things productive year after year.

Four-Field Systems

Splitting a plot into four different fields gives the advantage of growing even more crops at a time. But when the four-field system was first developed in the 1700s, there was more on the farmer’s mind than growing plants.

The concept calls for one of the fields to be left for a grazing crop, allowing farmers to maintain livestock year after year, in a more sustainable way. First developed in Belgium, the concept was crucial in the development of Europe’s dairy and meat industries.

How Do Crops Impact Each Other

Aside from spatial planning, the biggest trick of crop rotation is the symbiotic relationship between the plants—and balancing what each crop gives and takes from the soil.

George Washington Carver was a pioneer in the field, though more sophisticated tools of modern science have really helped take the concept up a notch. Today we understand many of the nuances involved in the relationship between plants, including:

Row Crops

The bread and butter on most farm operations, these are the crops that are typically grown and sold for profit.

Row crops are typically essential for farming operations – so they may have a more demanding nature on the soil that gets addressed by subsequent harvests. Popular types of row crops include corn, tomatoes, soybeans, hay and cotton.

Legumes

A crop rotator’s best friend, these plants offer a number of restorative properties to the soil.

Legumes – including plants like clover and alfalfa – will collect nitrogen from the air in concentrated doses, storing the vital plant-growing ingredient in special nodes in their roots, and therefore distributing more of it back into the soil. As many other types of crops are especially nitrogen-hungry, this is a particularly helpful trait.

But legumes also help the soil itself, with roots that tend to reach deep down. In turn, this pulls more soil up closer to the surface, working almost as a gentle underground tilling and making the soil more absorptive.

Grasses and Cereals

Called a “cover crop,” these plants are another staple of many crop rotation rhythms.

Grasses and cereals, such as oats and barely, typically have a dense, far-reaching root system that helps keep soil intact, and can spread nutrients evenly over wide swaths of land.

The crops also help as weed-fighting bumpers, as their roots take up so much room that it typically makes it difficult for anything else to grow.

It may be a little more engineered than many other more natural farming systems, like permaculture, but crop rotation is still a crucial tool in ensuring this earth can stick around—and keep growing food for us—as long as possible.