Living mulch - AbsoluteAstronomy.com

Agriculture

Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...

, a living mulch is a cover crop

Cover crop

Cover crops are crops planted primarily to manage soil fertility, soil quality, water, weeds, pests, diseases, biodiversity and wildlife in agroecosystems , ecological systems managed and largely shaped by humans across a range of intensities to produce food, feed, or fiber.Cover crops are of...

interplanted or undersown with a main crop

Agriculture

, and intended to serve the functions of a mulch

Mulch

In agriculture and gardening, is a protective cover placed over the soil to retain moisture, reduce erosion, provide nutrients, and suppress weed growth and seed germination. Mulching in gardens and landscaping mimics the leaf cover that is found on forest floors....

, such as weed

Weed

A weed in a general sense is a plant that is considered by the user of the term to be a nuisance, and normally applied to unwanted plants in human-controlled settings, especially farm fields and gardens, but also lawns, parks, woods, and other areas. More specifically, the term is often used to...

suppression and regulation of soil

Soil

Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

temperature

Temperature

Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...

. Living mulches grow for a long time with the main crops, whereas cover crops are incorporated into the soil or killed with herbicides.

Other benefits of mulches are slowing the growth of weeds, and protecting soil from water and wind erosion

Erosion

Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...

. Some living mulches were found to increase populations of the natural enemies of crop pests. Legumes used as living mulches also provide nitrogen fixation

Nitrogen fixation

Nitrogen fixation is the natural process, either biological or abiotic, by which nitrogen in the atmosphere is converted into ammonia . This process is essential for life because fixed nitrogen is required to biosynthesize the basic building blocks of life, e.g., nucleotides for DNA and RNA and...

, reducing the need for fertilizer.

Benefits

When cover crops are turned over into the soil, they contribute nutrients to the main crop so that less chemical fertilizer is required. The amount of the contribution depends on the biomass, which varies over time and depends on rainfall and other factors. The greater the biomass, the greater the nutrient turnover. Legume cover crops turn over nitrogen fixed from the atmosphere. Reports indicate that legumes in general have higher foliar nitrogen contents, from 20 to 45 mg g-1.

Bare soil resulting from intensive tillage can lead to soil erosion, nutrient losses, and offsite movement of pesticides. In addition, weeds can germinate and grow without competition. Living mulches can reduce water runoff and erosion, and protect waterways from pollution. Living mulches have also been shown to increase the population of organisms which are natural enemies of some crop pests.

Living mulches control weeds in two ways. When they are seeded before weed establishment, they suppress weeds by competition. In some situations, the allelopathic properties of living mulches can be used to control weeds. For example, the allelopathic properties of winter rye (Secale cereale), ryegrasses (Lolium spp), and subterrain clover (Trifolium subterraneum) can be used to control weeds in sweet corn (Zea mays var "rugosa") and snap beans (Phaseolus vulgaris).

Populations of ground-dwelling predators were greater in a corn and soybean rotation with alfalfa

Alfalfa

Alfalfa is a flowering plant in the pea family Fabaceae cultivated as an important forage crop in the US, Canada, Argentina, France, Australia, the Middle East, South Africa, and many other countries. It is known as lucerne in the UK, France, Australia, South Africa and New Zealand, and known as...

and kura clover living mulches than without a living mulch. This situation was due in part to a change in the composition of vegetation in the agricultural system.

Drawbacks

Unfortunately, living mulches compete for nutrients and water with the main crop, and this can reduce yields. For example, Elkins et al. (1983) examined the use of tall fescue (Festuca arundinacea), smooth bromegrass (Bromus inermis), and orchargrass (Dactylis glomerata) as living mulches. They found that herbicides killed 50% to 70% of the mulches but corn yield was reduced 5% to 10% at the end of the harvest.

Although leguminous cover crops have large biomass production and turnover, they are not likely to increase soil organic matter. This is because legumes used as living mulches have greater N contents and a low C to N ratio. So when legume residue decomposes, soil microbes have sufficient N available to enhance their breakdown of organic materials in the soil.

Types

In the tropics, it is common to seed tree crops with living mulches such as legume covers in oil palm

Oil palm

The oil palms comprise two species of the Arecaceae, or palm family. They are used in commercial agriculture in the production of palm oil. The African Oil Palm Elaeis guineensis is native to West Africa, occurring between Angola and Gambia, while the American Oil Palm Elaeis oleifera is native to...

plantations, coconut

Coconut

The coconut palm, Cocos nucifera, is a member of the family Arecaceae . It is the only accepted species in the genus Cocos. The term coconut can refer to the entire coconut palm, the seed, or the fruit, which is not a botanical nut. The spelling cocoanut is an old-fashioned form of the word...

and rubber (Watson 1989).

In Mexico

Mexico

The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

, legumes used traditionally as living mulches were tested as nematode

Nematode

The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...

and weed suppressors. The mulches included velvetbean (Mucuna pruriens
Mucuna pruriens
Mucuna pruriens is a tropical legume known as velvet bean or cowitch and by other common names , found in Africa, India and the Caribbean. The plant is infamous for its extreme itchiness produced on contact, particularly with the young foliage and the seed pods...

) jackbean (Canavalia ensiformis
Canavalia ensiformis
Canavalia ensiformis, or Jack-bean, is a legume which is used for animal fodder and human nutrition, especially in Brazil where it is called feijão-de-porco . It is also the source of concanavalin A.- Description :...

), jumbiebean (Leucaena leucocephala) and wild tamarindo (Lysiloma latisiliquum
Lysiloma latisiliquum
Lysiloma latisiliquum, commonly known as False Tamarind, is a species of tree in the pea family, Fabaceae, that is native to southern Florida in the United States, The Bahamas, the Caribbean, southern Mexico, and northern Central America....

). Aqueous extract of Velvetbean reduced the gall index of Meloidogyne incognita
Meloidogyne incognita
The Meloidogyne incognita is a nematode, a type of roundworm, in the family Heteroderidae. It is an important plant parasite classified in parasitology as a root-knot nematode, as it prefers to attack the root of its host plant....

in the roots of tomato

Tomato

The word "tomato" may refer to the plant or the edible, typically red, fruit which it bears. Originating in South America, the tomato was spread around the world following the Spanish colonization of the Americas, and its many varieties are now widely grown, often in greenhouses in cooler...

, but suppressed tomato rooting as well. In addition, Velvetbean suppressed the radical growth of the local weeds Alegria (Amaranthus hypochondriacus
Amaranthus hypochondriacus
Amaranthus hypochondriacus is an ornamental plant commonly known as the Prince-of-Wales-feather or the Prince's feather. It is originally from Mexico where it is endemic where it is called Quelite, Blero. and Quintonil...

) by 66% and Barnyardgrass (Echinochloa crus-galli
Echinochloa crus-galli
Echinochloa crus-galli is a type of wild grass originating from tropical Asia that was formerly classified as a type of panicum grass. It is commonly known as Cockspur , Common Barnyard Grass, or simply "barnyard grass"...

) by 26.5%.

Nicholson and Wien (1983) suggested the use of short turfgrasses and clover

Clover

Clover , or trefoil, is a genus of about 300 species of plants in the leguminous pea family Fabaceae. The genus has a cosmopolitan distribution; the highest diversity is found in the temperate Northern Hemisphere, but many species also occur in South America and Africa, including at high altitudes...

s as living mulches to improve the resistance soil compaction. These authors established Smooth Meadow-grass (Poa pratensis) and white clover (Trifolium repens) as living mulches since they did not caused reduction of yield corn (the accompanying main crop).

In one study, chewing fescue or red fescue (Festuca rubra
Festuca rubra
Festuca rubra is a species of grass known by the common name red fescue. It is found worldwide and can tolerate many habitats and climates; it generally needs full sun to thrive...

) and ladino clover (Trifolium repens) were effective living mulches for controlling weed growth. Unfortunately, these cover crops also competed with corn for water which was particularly problematic during a dry period. The possibility of using ladino clover (Trifolium repens) as a potential living mulch was also mentioned; however, this clover was difficult to kill with herbicides in winter.

Management

Because they compete with the main crop, living mulches may eventually need to be mechanically or chemically killed.

It is important to judiciously select the appropriate herbicide rate for burning down a living mulch. In 1989, Echtenkamp and Moomaw found that herbicide rates were inadequate to suppress all the living mulches. Therefore, the mulches competed with the main crop for resources. In some cases, the clover could not be killed at the first herbicide application, so a second application was needed. For another treatment, rates that were so high that they caused the cover crop to be killed too rapidly, so that broadleaf weeds invaded the corn. This study suggested that the timing and dosage of herbicide should be carefully considered.

Living mulches were tested in a no-till corn-production systems with two methods for establishing grass and legume living mulches (grass and legume) between corn rows. In 1985, there was no difference between drilling and broadcasting seeds by hand in that study. However in 1986, drilling resulted in higher populations (97 plants m-2) than broadcasting (64 plants m-2), likely because of precipitation levels. Precipitation should be considered because farmers have no control over it.

Beard (1973) recommended chewing fescue (red fescue) (Festuca rubra var "commutata" var "shadow FESRU") as a good living mulch because it adapts to the shady conditions under corn and soybean. This grass is also well adapted to dry and poor soils.

Plant nutrition

Legume cover crops have important positive effects on the nutrient cycling of tree crops. Leguminous living mulches work in three ways:

Fixing the atmospheric N2 that is important for the main crop,
Recycling soil nutrients, and
Enhancing soil nutrient availability for the main crop.

Lehmann et al. (2000) measured the above ground biomass accumulation of Pueraria phaseoloides, which is a living mulch used in tropical tree crops. They found that Pueraria accumulated 838 mg of dm (dry matter) ha-1 as compared with 4.4 mg dm ha^-1 for Theobroma grandiflorum, and 1.4 mg dm ha-1 for Bactris gasipaes. These latter two species are native cultivated species from the Amazon.

Control of erosion

Vegetative cover as living mulches protect soil against wind and water erosion. Plants should form a mantle or thick mulch that protect soil from detachment. Living mulches intercept raindrops and reduce runoff. The protection that such vegetation provides against wind is influenced mainly by the amount of biomass that covers the ground (differs with each spp), plant geometry and row orientation.

In one experiment, water runoff and soil loss on a 14% slope was compared for rototilled (RT), no-till with corn stover mulch (NTCMS), no-till in CSM+ birdsfoot trefoil living mulch (NT-BFT) and no till in CSM and crownvetch living mulch (NT-CV). The results indicated that the water runoff was 6,350 L ha-1 for NT-BFT, 6,350 L ha-1 NO-CSM, 5,925 L ha-1 for NT-CV, and 145,000 L ha-1 for RT. The soil loss for the RT was 14.22 t ha-1 while with the other treatments it was less than 0.5 tons ha-1. The least soil loss was obtained with NT-CV 0.02 tons ha-1. The reduction of water runoff and erosion is one of the greatest advantages of having a cover crop. Soil can be easily eroded with no vegetative ground cover or plant residue. Ideally soil erosion should be less than 4 to 5 tons/ha/year.

Neutral articles

Positive studies

Alfalfa living mulch advances biological control of soybean aphid

Negative studies

Cucumber Production reduced yields

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