Monocropping is the agricultural practice of growing a single crop year after year on the same land, in the absence of rotation through other crops or growing multiple crops on the same land (polyculture). Corn, soybeans, and wheat are three common crops often grown using monocropping techniques.
While economically a very efficient system, allowing for specialization in equipment and crop production, monocropping is also controversial, as it can damage the soil ecology (including depletion or reduction in diversity of soil nutrients) and provide an unbuffered niche for parasitic species, increasing crop vulnerability to opportunistic insects, plants, and microorganisms. The result is a more fragile ecosystem with an increased dependency on pesticides and artificial fertilizers. The concentrated presence of a single cultivar, genetically adapted with a single resistance strategy, presents a situation in which an entire crop can be wiped out very quickly by a single opportunistic species. An example of this would be the potato famine of Ireland in 1845–1849, and according to Devlin Kuyek is the main cause of the current food crisis with monoculture rice crops failing as the effects of climate change become more acute.
Monocropping as an agricultural strategy tends to emphasize the use of expensive specialized farm equipment—an important component in realizing its efficiency goals. This can lead to an increased dependency on fossil fuels and reliance on expensive machinery that cannot be produced locally and may need to be financed. This can make a significant change in the economics of farming in regions that are accustomed to self-sufficiency in agricultural production. In addition, political complications may ensue when these dependencies extend across national boundaries.
The controversies surrounding monocropping are complex, but traditionally the core issues concern the balance between its advantages in increasing short-term food production—especially in hunger-prone regions—and its disadvantages with respect to long-term land stewardship and the fostering of local economic independence and ecological sustainability. Advocates of monocropping tend to claim that in its absence many human populations would be reduced to starvation or to a degraded level of civilization comparable to the Dark Ages. On the other hand, critics of monocropping dispute these claims and attribute them to corporate special interest groups, citing the damage that monocropping causes to societies and the environment.
A difficulty with monocropping is that the solution to one problem—whether economic, environmental or political—may result in a cascade of other problems. For example, a well-known concern is pesticides and fertilizers seeping into surrounding soil and groundwater from extensive monocropped acreage in the U.S. and abroad. This issue, especially with respect to the pesticide DDT, played an important role in focusing public attention on ecology and pollution issues during the 1960s when Rachel Carson published her landmark book Silent Spring.
Soil depletion is also a negative effect of mono-cropping. Crop rotation plays an important role in replenishing soil nutrients, especially atmospheric nitrogen converted to usable forms by nitrogen-fixing plants used in fallow fields. In addition, it performs an important role in preventing pathogen and pest build-up. In a monocropping regime, farmers are less likely to rotate their crops and replenish such essential soil nutrients. In addition, artificial high-nitrogen fertilizers can "burn" the soil by creating an unfavorable environment for indigenous organisms, a phenomenon well-known to organic gardeners and farmers (who avoid it), resulting in further disruption of soil ecology and dependence on further short-term fertilizer strategies. Lacking a stable ecology, in the absence of substantial irrigation and chemical "fixes" the soil can become dry and begin to erode. As the soil becomes arid and useless, the need for more land becomes an issue, leading to the destruction of even more land—a high-tech version of slash and burn agriculture.
Under certain circumstances monocropping can lead to deforestation or the displacement of indigenous peoples.
In order to help reduce dependence on fossil fuels the U.S. government subsidizes the monocropping of corn and soybeans to be used in ethanol production. However, monocropping itself is highly chemical- and energy-intensive, as studies by Nelson (2006) indicate. Such studies have shown that the "hidden" energy costs associated with producing each unit of bio-fuel are significantly larger than the amount of energy available from the fuel itself.