Updated: Crop Rotation for Intensive Growing Systems

 

Since the demand for four specific crops have taken priority this year, and probably for the foreseeable future, crop rotation is becoming even more important. Of course, three out of the four crops are heavy nutrient feeders (corn, tomatoes, and potatoes), with only one crop (beans) being one that naturally reintroduces nitrogen into the soil. While market demand calls for more and more of the crops that tax the soil heavily, how can crop rotation in an intensive system satisfy demand without sacrificing soil quality? 

Well, to start, crop rotation is an important aspect to agriculture, whether in small or large applications. It can be even more important dependent on what crops are to be grown, since some crops remove more nutrients from the soil than others. Some crops have effects on proceeding crops due to compounds that are released into the soil during their growth cycle. A prime example of this would be rye grass. Rye grass produces an allelopathic effect (chemical release that inhibits the germination of nearby seeds/seedlings) on its immediate surroundings, which make rye grass a great cover crop to suppress weeds. However, it may not be beneficial to plant into a living rye cover crop, unless the rye has been killed off/tilled in; but, that doesn't discard the benefits rye provides, such as organic matter, nitrogen, and weed suppression, which are useful for proceeding crops. 

Planting "heavy feeding" crops in the same area year after year (corn, tomatoes, cabbage), while they may be from different crop families, will tax the soil of nutrients like nitrogen, which will ultimately make unhealthy plants with low yields. Of course, fertilizers or compost can be added to replace the lost nutrients, but the ideal system that is desired is one that needs little outside inputs; instead, the inputs that are needed are farm-generated. 

Let's take the crop rotation of a stereotypical midwestern farm: corn and soybeans. While there are other factors that influence this specific crop rotation (like agricultural subsidies), the fundamental idea behind this rotation is that corn is a nitrogen feeder, and soybeans are a nitrogen giver. However, without the advent of artificial fertilizers, this rotation would not be able to survive (and there are still major problems associated with soil health because of corn-soybean rotations) because soybeans can't produce enough nitrogen for corn, which would lead to a nitrogen debt if it weren't for artificial fertilizers and/or an abundance of animal manure. But, needless to say, just a corn-soybean rotation is not sustainable by itself. 

Some crop rotations are influenced by environmental conditions, but its generally a good rule of thumb to not plant heavy feeding plants right after another. I try to not plant, for example, corn and tomatoes, in the same place without at least a year of beans or peas between the plantings. However, I recently came across some information that said that planting potatoes after corn will result in a higher potato yield. How? I don't know yet, but am eager to see if it works! 

So far, we've talked about how crop rotation is necessary to preserve/build nutrients in the soil, but what does crop rotation do to plants themselves? Like I mentioned above about how potatoes might yield more after corn, plants can both offer benefits and detriments to proceeding crops. Whether that be nitrogen fixing potential (alfalfa, beans, peas, ect...), or soil preparation qualities (root crops that go deep into the soil and loosen it), there are a wide variety of crops that can benefit a proceeding one. Another key benefit, maybe more so a necessity, is the reduction of pests, weeds, and diseases. By developing a larger crop rotation, or just a better management of an existing rotation, pests, weeds, and diseases can be kept to a minimum because they cannot gain a foothold when a piece of land has a different crop on it for several years. Some weeds are more partial to some crops versus others, as well as diseases and pests. So, by shaking up the cycles of pests and diseases with crop rotation, pesticides and excessive cultivation for weed control can be kept at a minimum, which also saves money and time! 

Cover crops can also fill in as a crop, which can give the soil a "rest," and replenish soil quality. I have been experimenting with cereal grasses as cover crops, and haven't seen any negative results so far, but am eager to see if there are other cover crops, like peas or alfalfa, that would aid the soil given the current demand for heavy-feeding crops. 

Crop rotation is important for any style of grower. While having a large supply of sweet corn and tomatoes every year might be desired, is it necessary to degrade your soil for years to come or could some other vegetables fit into the existing rotation? It doesn't take much to destroy the natural cycles of the soil, but it does take a lot to repair. In this instance, and ounce of prevention is worth a pound of cure for sure!