agriculture Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people t ...

, a living mulch is a cover crop interplanted or undersown with a main

crop A crop is a plant that can be grown and harvested extensively for profit or subsistence. When the plants of the same kind are cultivated at one place on a large scale, it is called a crop. Most crops are cultivated in agriculture or hydropon ...

, and intended to serve the purposes of a

mulch A mulch is a layer of material applied to the surface of soil. Reasons for applying mulch include conservation of soil moisture, improving fertility and health of the soil, reducing weed growth and enhancing the visual appeal of the area. A mu ...

, such as

weed A weed is a plant considered undesirable in a particular situation, "a plant in the wrong place", or a plant growing where it is not wanted.Harlan, J. R., & deWet, J. M. (1965). Some thoughts about weeds. ''Economic botany'', ''19''(1), 16-24. ...

suppression and regulation of

soil Soil, also commonly referred to as earth or dirt Dirt is an unclean matter, especially when in contact with a person's clothes, skin, or possessions. In such cases, they are said to become dirty. Common types of dirt include: * Debri ...

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measurement, measured with a thermometer. Thermometers are calibrated in various Conversion of units of temperature, temp ...

. 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 is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is dis ...

. Some living mulches were found to increase populations of the natural enemies of crop pests.Hartwig N.L., H.. Ammon 2002 Cover crops and living mulches Weed Sci. 50: 688-699 Legumes used as living mulches also provide

nitrogen fixation Nitrogen fixation is a chemical process by which molecular nitrogen (), with a strong triple covalent bond, in the air is converted into ammonia () or related nitrogenous compounds, typically in soil or aquatic systems but also in industry. Atmo ...

, 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.Brophy L. S., G. H. Heichel and M.P. Russelle. 1987 Nitrogen transfer from forage legumes to grass in a systematic planting design Crop Sci 27: 753-758 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 of land. 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.Lehmann J, J.P. da Silva, Jr. L. Trujillo, K. Uguen 2000 Legume cover crops and

nutrient cycling A nutrient cycle (or ecological recycling) is the movement and exchange of inorganic and organic matter back into the production of matter. Energy flow is a unidirectional and noncyclic pathway, whereas the movement of mineral nutrients is cycli ...

in tropical fruit tree production Acta Horticulturae 531: 35-72. 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.Hartwig N.L 1977 Nutsedge control in no-tillage corn with and without a crownvetch cover crop. Proc. Northeast. Weed Sci. Society 31: 20-33 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'').De Gregorio R. E. and R.A. Ashley. 1986. Screening living mulches/ cover crops for no-till snap beans. Proc. Northeast. Weed Sci. Soc. 40:87-91 Populations of ground-dwelling predators were greater in a corn and soybean rotation with alfalfa and kura clover living mulches than without a living mulch.Prafiska J. R, N. P Schmidt, and K.A Kohler, 2006 Effects of living mulches on predator abundance and sentinel prey in a corn-soybean-forage rotation Env. Entomology 35: 1423-1431 This situation was due in part to a change in the composition of vegetation in the agricultural system.Andow 1991. Vegetational diversity and arthropod population response. Annu. Rev. Entomol. 36: 561- 586.

Drawbacks

Unfortunately, living mulches compete for nutrients and water with the main crop,Echtenkamp, G. W, and R. Moomaw 1989 No-till corn production in a living mulch system Weed technology 3: 261-266 and this can reduce yields. For example, Elkins et al. (1983) examined the use of tall fescue (''

Festuca arundinacea ''Festuca arundinacea'' ( syn., ''Schedonorus arundinaceus'' and ''Lolium arundinaceum'') is a species of grass commonly known as tall fescue. It is a cool-season perennial C3 species of bunchgrass native to Europe. It is an important forage g ...

''), smooth bromegrass ('' Bromus inermis''), and orchargrass (''

Dactylis glomerata ''Dactylis Glomerata'' is the sixth studio album by Swedish doom metal band Candlemass, released in 1998. This was their first album released since their split in 1994. The album was originally destined to be the second release by Candlemass m ...

'') 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.Elkins, D., D. Frederking, R. Marashi, and B. McVay. 1983. Living mulch for no-till corn and soybeans. J. soil Water Conserv, 38: 431-433 Although leguminous cover crops have large biomass production and turnover, they are not likely to increase soil organic matter.Barber, R.G., and F. Navarro 1994. The rehabitation of degraded soils in eastern Bolivia by subsoiling and the incorporation of cover crops. Land Degr. Rehab. 5:247-259 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 ''Elaeis'' () is a genus of palms containing two species, called oil palms. They are used in commercial agriculture in the production of palm oil. The African oil palm '' Elaeis guineensis'' (the species name ''guineensis'' referring to its c ...

plantations,Broughton W.J., 1977. Effects of various covers on soil fertility under Hevea brasiliensis and on growth of the tree. Agro-Ecosys. 3:147-170 coconutAldaba F.R., 1995. Coconut production in the Philippines: problems and prospects. Plantatios, Recherche, Developpement Sept-Oct:15-18 and rubber.Watson G.A., 1989a. Field maintenance. In: Webster, C.C. (Ed.), Rubber. Longman Scientific, London. pp. 245-290. In

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

, legumes used traditionally as living mulches were tested as nematode and weed suppressors.Caamal-Maldonado J.A.,Jimenez J.J., Torres A., Anaya A. 2001. The use of allelopathic legume cover and mulch species for weed control in cropping systems. Agron J. 93:27-36 The mulches included velvetbean ('' Mucuna pruriens'') jackbean ('' Canavalia ensiformis''), jumbiebean (''

Leucaena leucocephala ''Leucaena leucocephala'' is a small fast-growing mimosoid tree native to southern Mexico and northern Central America (Belize and Guatemala) and is now naturalized throughout the tropics including parts of Asia. Common names include jumbay, ...

'') and wild tamarindo (''

Lysiloma latisiliquum ''Lysiloma latisiliquum'', commonly known as false tamarind or wild tamarind, is a species of tree in the family Fabaceae, that is native to southern Florida Florida is a state located in the Southeastern region of the United States. Fl ...

'').

Aqueous An aqueous solution is a solution in which the solvent is water. It is mostly shown in chemical equations by appending (aq) to the relevant chemical formula. For example, a solution of table salt, or sodium chloride (NaCl), in water would be re ...

extract of Velvetbean reduced the gall index of ''

Meloidogyne incognita ''Meloidogyne incognita'' (root-knot nematode - RKN), also known as the "southern root-nematode" or "cotton root-knot nematode" is a plant-parasitic roundworm in the family Heteroderidae. This nematode is one of the four most common species world ...

'' in the roots of

tomato The tomato is the edible berry of the plant ''Solanum lycopersicum'', commonly known as the tomato plant. The species originated in western South America, Mexico, and Central America. The Mexican Nahuatl word gave rise to the Spanish word ...

, but suppressed tomato rooting as well. In addition, Velvetbean suppressed the radical growth of the local weeds Alegria (''

Amaranthus hypochondriacus ''Amaranthus hypochondriacus'' is an ornamental plant commonly known as Prince-of-Wales feather or prince's-feather. Originally endemic to Mexico, it is called ''quelite, bledo'' and ''quintonil'' in Spanish. In Africa and El Salvador, like many ...

'') by 66% and Barnyardgrass (''

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 (or cockspur grass), barnyard millet, Japanese millet, water grass, common ...

'') by 26.5%. Nicholson and Wien (1983) suggested the use of short

turfgrass A lawn is an area of soil-covered land planted with grasses and other durable plants such as clover which are maintained at a short height with a lawnmower (or sometimes grazing animals) and used for aesthetic and recreational purposes. ...

es and

clover Clover or trefoil are common names for plants of the genus ''Trifolium'' (from Latin ''tres'' 'three' + ''folium'' 'leaf'), consisting of about 300 species of flowering plants in the legume or pea family Fabaceae originating in Europe. The genus ...

s as living mulches to improve the resistance soil compaction. These authors established Smooth Meadow-grass (''

Poa pratensis ''Poa pratensis'', commonly known as Kentucky bluegrass (or blue grass), smooth meadow-grass, or common meadow-grass, is a perennial species of grass native to practically all of Europe, North Asia and the mountains of Algeria and Morocco. Altho ...

'') and white clover (''

Trifolium repens ''Trifolium repens'', the white clover, is a herbaceous perennial plant in the bean family Fabaceae (otherwise known as Leguminosae). It is native to Europe, including the British Isles,Clapham, A.R., Tutin, T.G. and Warburg., E.F. 1968. ''Excursio ...

'') as living mulches since they did not cause reduction of yield corn (the accompanying main crop).Nicholson, A.G., and H.C. Wein. 1983. Screening of turfgrasses and clovers for use as living mulches in sweet corn and cabbage . J. Am Soc. Hort. Sci. 108:1071-1076 In one study, chewing fescue or red fescue (''

Festuca rubra ''Festuca rubra'' is a species of grass known by the common name red fescue or creeping red fescue. It is widespread across much of the Northern Hemisphere and can tolerate many habitats and climates. It is best adapted to well-drained soils in c ...

'') 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.Brandsaeter, L. J. Netland, and R. Meadow 1998 Yields, weeds, pests and soil nitrogen in a white cabbage living mulch system, in Biol. Agric. Hortic. 16: 291-309Tharp, B. e., and J. J. Dells. 2001 Delayed burndown in no-tillage glyphosate-resistant corn (Zea mays) planted into soybean (Glycine max) residue and a wheat (Triticum aestivum) cover crop. Weed Technol. 15: 467-473 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.Beard, J. 1973 Turfgrass: Science and Culture Prentice-Hall Inc. Englewood Cliffs, NJ 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 ''Neustanthus'' is a monotypic genus of flowering plants belonging to the pea family Fabaceae and its tribe Phaseoleae. The only species is ''Neustanthus phaseoloides'', called tropical kudzu. This species is a forage crop and cover crop used ...

'', which is a living mulch used in tropical tree crops. They found that ''Pueraria'' accumulated 8.8 metric ton of dm (dry matter) ha-1 as compared with 4.4 t dm ha⁻¹ for ''

Theobroma grandiflorum ''Theobroma grandiflorum'', commonly known as cupuaçu, also spelled cupuassu, cupuazú, cupu assu, or copoazu, is a tropical rainforest tree related to cacao. Native and common throughout the Amazon basin, it is naturally cultivated in the jung ...

'', and 1.4 t dm ha-1 for ''

Bactris gasipaes ''Bactris gasipaes'' is a species of palm native to the tropical forests of Central and South America. It is well spread in these regions, where it is often cultivated by smallholders in agroforestry systems or more rarely, in monoculture. Commo ...

''. 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.Trohen F and J.A. Hobbs 1991 Soil and water conservation 1991 4:83-84 and 5: 108-109 Prentice Hall Inc. Englewood Cliffs, NJ In one experiment, water runoff and soil loss on a 14% slope was compared for rototilled (RT), no-till with corn stover mulch (NT-CSM), 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 NT-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.Hall J, L. Hartwing, and L. Hoffman 1984 Cyanazine losses in runoff from no-tillage corn in "living mulch" and dead mulches vs. unmulched conventional tillage. J. Envoron. Qual 13: 105-110 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.Pimentel D., C. Harvey, P. Resosudarmo et al., 1995 Environmental and economic costs of soil erosion and conservation benefits. Science 267: 1117-1122

References

External links

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Neutral articles

Living Mulch by Dr. Mary Peet, NCSU

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Alfalfa living mulch advances biological control of soybean aphid

Why I Chose White Clover as a Living Mulch

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