Title: Cover Crops

 
A field of cover crops: in between the collards in this field is a cover crop mix of rye, hairy vetch and crimson clover, which provides a lush cover protecting the soil from harsh winds and eroding/compacting rains. Source: TILLER (2012 & SSWM)
 
Cover crops can be used on fallow land, grown between cash-crop rotations, intercropped with other crops, as green manure or as a living mulch. Crop covers suppress weeds, maintain and improve soil fertility and prevent soil erosion. For instance, an effective cover crop at suppressing weeds in hazelnut (Corylus avellana) production is oriental mustard.

Cover crops can be used in different ways. Some cover crops are grown with crops while others are grown on fallow land and removed before crop planting. Different cover crops have different uses, benefits and characteristics. For instance some cover crops fix nitrates into the soil making it available to companion crops, while others act as weed suppressors.

Cover crops are also beneficial to land which is to lay fallow fixing it with nitrates, preventing soil erosion and suppressing weed infestation. Weeds can also be used as a cover crop to prevent other more destructive weeds from taking hold.

Cover crops which have been harvested can be used as forage or as mulch for subsequent plantings. The mulch then acts to suppress future weeds while enriching the soil with nitrogen and microbes. Due to possible allelopathtic action of mulched cover crops an understanding of which cover crops work best with which crops becomes essential. A viable option is to mulch the compost before use.

How to Choose a Cover Crop

Cover crops can be planted, either during the cropping season (to cover the area in between the crop rows), or afterwards to cover the whole field. During the cropping season, the crops themselves act as soil cover. An intercrop of tall plants (such as maize) and low-growing plants (such as beans) make a good cover. It can be difficult to keep the soil covered, especially in semi-arid areas. It may be necessary to compromise: some cover is better than none.

Growing cover crops is a common soil management practice. There are a lot of good reasons to grow cover crops but it is often hard to put a dollar value on the return from growing them. Cover crops are an important part of a system of soil maintenance - particularly important on the lighter soils with lower organic matter or on fields with short rotations and little return of crop residue or manure. It is important to know the goal when planting a cover crop and to select the best one for that job. Small-scale farmers prefer a cover crop which fits into their normal cropping system and which has multiple purposes



First, check which cover crops grow well in your area. This depends on the soil type, rainfall, temperature and altitude. If you live in an area with little rainfall, select a cover crop that grows quickly, such as cowpea, desmodium, lablab, lucerne, mucuna, or pigeonpea. Then check how much work each cover crop will need: for land preparation before planting, weeding, and producing and harvesting the seeds. Species with big pods and grains (such as pigeonpea and mucuna) are easier to deal with than species with small pods (such as vetch and grasses). Most farmers prefer species that cover the soil quickly and completely, and which can also be used for food and fodder. As a support to decide which cover crop is suitable and when it should be planted, FAO (2005) recommends answering the following questions:









Questions about the cropping system:



As already mentioned, it is important to know the goal when planting a cover crop and to select the best one for that job. The following table looks at the various reasons for including cover crops in a rotation and the potential cover crops that best meet those goals. These may vary for other climates and countries.

Cover Crop Function

Best Choices for Cover Crops

Nitrogen production

Legumes - red clover, peas, vetch

Nitrogen scavenging

Fall uptake - oilseed radish and other brassicas, oat

Winter/ spring uptake - rye, winter wheat

Weed suppression

Fast growing/shading plants - oilseed radish and other brassicas, winter rye, buckwheat

Soil structure building

Grasses - oat, barley, rye, wheat, triticale, ryegrass or fibrous root systems such as red clover

Compaction reduction

Strong tap roots that grow over time - alfalfa, sweet clover

Biomass

Fall seeded - oat, oilseed, radish Summer-seeded - millets, sorghum, sudangrass, sorghum sudan

Erosion protection, i.e., wind, water

Winter rye, winter wheat, ryegrass (well-established), springcereals seeded early

Emergency forage

Fall - oat, barley, wheat, rye, forage brassicas

Summer - millets, sorghum, sudangrass, sorghum sudan

Nematode suppression

Cutlass mustard, sudans/sorghums, pearl millet, marigold (Crackerjack, Creole), oilseed radish (Adagio, Colonel)

Note: Not all cover crops have the ability to suppress nematode populations; some will even act as hosts. Cover crop activity is variety- and nematode-specific. To get the most activity, cover crops should be weed free and may require specific handling.


Source

Cover Crop Decision Tool





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referenced by (1)
SustainableWeedingGuide212: Index
Article: CulturalWeedControl228 (permalink)
Date: 10 January 2013; 2:58:44 PM AEDT

Author Name: Zheljana Peric
Author ID: zper12