Tracing Crop Rotations Through Time: A Search for Sustainability
“The challenge for the present is to learn to factor in the future, to think in the long term, and to put humans’ tremendous creative power to work to design an agriculture that reflects nature’s patterns and integrates itself into the natural cycles of the ecosphere, an agriculture that runs on sunshine and consumes only the fruits of the land, an agriculture that, with proper stewardship, will endure forever.”
The harsh conditions of the dust bowl, the decrease in family farming, and the runoff of cheap fertilizers into our water supply illustrate consequences that have arisen out of what were thought to have been well-devised solutions. Each effect has proven the importance and impact that agriculture has on our environment and society, as well as the need for ecological cycles to be taken into account when decisions dealing with the environment are being made.
“It must be recognized that ultimately any economy is based on how human beings make a living here on the earth, and on all human relationships with the things of the earth – with organisms and with inert materials, with processes and cycles that link all parts of the ecosphere (Soule and Piper 1992).”
When commercial agriculture was introduced the impacts that it would have on the soil were not thoroughly known. The fact is that soil, repeatedly cultivated with a single crop, gets stripped of nutrients if it is not allowed any break during which other vegetation is planted that can replace those lost nutrients, therefore enriching the soil. This is the reason crop yields are reduced on monocropped fields. The cash crops such as corn, cotton, and wheat all take nutrients from the soil in order to grow and produce the grain and seed that we humans so desire. The soil only has so many of these nutrients and without other nutrient replenishing crops or vegetation grown in that soil the productivity gets reduced. Hence, there are fewer and fewer nutrients available to the crops and they are therefore unable to produce high yields. The soil becomes increasingly less productive leading to soil erosion problems. More specifically eroded soils have low nitrogen contents, impaired soil structure, deficient organic matter, and reduced availability of moisture (Jackson, Berry, and Colman 1984). All these conditions impair crops from producing to their utmost capacity.
After the dust bowl the need for well-fertilized soil with nitrogen levels became widely known. Chemical fertilizers were developed after industries that had been producing explosives during World War II found themselves without a market at the end of the war. Nitrogen was added to these fertilizers in order replenish the soil and increase crop yields. In addition, after the war these fertilizers became so cheap that all farmers could use them (Soule and Piper 1992). However, this cheap fertilizer came at the expense of many unforeseen losses.
First of all, cheap fertilizer contributed to the departure of animals from farms, since their manure was no longer needed. This sequentially led to the removal of pasture crops on farms, which were helpful in keeping soil fertility, preventing soil erosion, and beneficial in crop rotations.
Second, nitrogen rich fertilizers create a problem called nitrogen leaching. Most farmers apply more fertilizer than their crops can use and so the excess drains down into the groundwater polluting it. The nitrate in the fertilizer is toxic to infants and if ingested in high enough concentrations can lead to the fatal “blue baby syndrome.” Two research studies performed from 1990 to 1993, by Kanwar et al. and Melvin et al., prove that crop rotation helps to alleviate or at least greatly reduce nitrogen leaching. The Melvin et al. study also emphasized that a simple corn-soybean rotation might not be as beneficial as a more diverse rotation. By using a more diverse rotation that follows shallow-rooted crops with deep-rooted crops the nitrogen that has proceeded down to deeper soil zones can be retrieved by the deep roots (Soule and Piper 1992).
In addition, nitrogenous fertilizers end up hiding soil erosion. In fact, these fertilizers actually increase the process of soil erosion albeit through less direct means. By adding nitrogenous fertilizers to the soil organic matter is reduced because the fertilizer stimulates decomposition. This effect, in turn, leads to a change in soil composition that affects the soils ability to hold moisture, which, in turn, leads to soil compaction and vulnerability to erosion (Soule and Piper 1992).
Finally, cheap fertilizers brought about the exit of crop rotations that included legumes. Legumes are plants that work with bacteria to take nitrogen from the air and transfer it to the soil in a process called nitrogen fixation. Alfalfa is a perennial legume that was used by many settlers in their crop rotations specifically for this nitrogen fixation capability. The plant served as feed for their animals and helped to keep their soil fertile and productive (Bakko). In a study performed in Minnesota in 1996 by Sharma et al. alfalfa was found to improve the productivity of soil and the downstream water quality when used in rotation with corn and soybeans. Since fields with legumes require less inputs, especially fertilizer inputs, runoff is sequentially decreased. More research is needed to determine the true capabilities and benefits of legumes in rotations, but unfortunately funding for such research lies in direct competition with biotechnology.
Currently our agricultural system demands high amounts of inputs (fertilizers, herbicides, pesticides, ect.) and heavy, expensive machinery. This method is unsustainable and unhealthy for the environment and for humanity. Farmers seem to be trapped is a cycle where the more inputs used the more are needed. For the suppliers of these products this is a good cycle for business, but for the farmers and all individuals, including non-human beings, that, through living in this world, are affected by its agricultural processes this cycle is leading towards a dangerous and unstable future. Sustainable agricultural methods need to be renewed and popularized once again. We need to re-learn all the benefits that come from these sustainable farming practices from our ancestors who knew the wisdom behind such practices as crop rotation. Crop rotation can save farmers from becoming trapped in the inescapable cycle of increasing inputs. With a return to the more traditional methods of farming the connection between farmer and land can be re-established benefiting ecological and human communities alike.