Image Caption: Painter of the burial chamber of Sennedjem. A Plowing Farmer. Credit: Yorck Project/Wikipedia
Cover crops are crops that are planted to improve the quality of the soil, also known as green manure. Cover crops add fertility to the soil, control weeds and pests as well as control diseases that can be otherwise found in untreated soil. Cover crops increases the organic matter levels in the soil which only enhances the structure of the soil as well as increase the capacity for holding water. The control of wildlife is also necessary in order to have a well-balanced agroecosystem; the study of the relation of agricultural crops and environment.
Cover crops are chosen based on the needs and goals of the farmer as well as the crop that will grow best in the given environment.
Uses of cover crops
Adding fertilizer to the soil is the main reason for growing cover crops. Cover crops are grown over a short resting period between cash crops and then are plowed back into the soil. This process replaces nutrients, especially nitrogen, back into the soil and ready to be absorbed by the cash crop.
Cover crops in the pea/bean family are high in nitrogen and are generally used in crop rotation. These types of crops have a bacteria called rhizobial which lives in the root nodules of the crop that then interacts with the roots of the cash crop creating a symbiotic relationship between the two. The bacteria changes the atmospheric nitrogen gas (N2) that is biologically unavailable to the plants into an ammonium (NH4+) that is biologically acceptable. The process is called nitrogen fixation.
Scientists believe that nitrogen fixation is better achieved through the use of cover crops versus the use of industrial nitrogen fixation. The use of cover crops helps to maintain as well as increase the production of future food levels. Industrial nitrogen fixation has had widespread impacts on the environment which includes nitrogen being released into waterways. Too much nitrogen can cause large bodies of water to lose oxygen which would have continued ecological damage.
Catch crops can be grown in succession with another crop or planted in between the spring and fall plantings of cash crops. A catch crop “catches” the unused nitrogen from the previous crop and prevents it from being flushed out of the soil. Fast growing catch crops such as millet, is fast growing and easily turned into green manure.
Cover crops that are used as mulch (left on top of the ground to decompose) help to reduce the weed population by blocking out the light that is needed for weed seed germination. Leaving the mulch also increases the moisture level in the soil which is useful in dry climate areas but can be problematic in wet climate areas.
Cover crops are also used to break the disease cycle by reducing the population of parasitic nematodes as well as any fungal or bacteria causing diseases. Mustards, broccoli, cabbage and radishes are just a few crops that have been known to lessen the presence of fungal disease.
An organic method of controlling pest is to plant trap crops. Trap crops are planted at the same time as the cash crop only in a different area. The idea is to lure the pests away from the cash crop, lessening the damage to important crops, and then ridding the trap crop of the pest by vacuuming the plants and removing the pest from the fields. A non-organic method would be to spray the trap crop with a pesticide.
Cover crops are not only beneficial for nitrogen fixation, weed control, or pest control, but also to the wildlife native to the locality of the cover crop. Cover crops do not usually have a value and can be left unattended until it is time to turn it back into the soil. For instance, the song bird population increased over cover crops of clover for cotton fields. The cover crop supplied nesting sites and ground cover along with an endless supply of food.