Mulch

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Mulch

• Best When Suited to Place
• Heidi Dunn

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Mulch for the Home Garden/Small Farm

• Types Used
• Straw
• Leaves
• Grass clippings
• Bark
• Plastic Sheets-Black, and now colored.
• Whatever else is available-Neighbors scraps?
• It is best to use whatever is most available in
  your area to be more cost efficient and
  environmentally sound.
  

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Mulch for the Home Garden/Small Farm

• Functions
• Weed suppression-labor reduction
• Moisture retention
• Erosion control
• Soil temperature moderation
• Nutrient cycling/reduced need for soil
  amendments
  
• Yield enhancement

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Mulch For the Home Garden/Small Farm

• Cold Climates
• Mulch should be applied in late spring.
• Soil temperature must be warm before applying
  mulch in the spring or growth will be slowed.
  
• Mulch can host certain diseases in wet climates
  if managed incorrectly.
  

• Hot/Dry Climates
• Mulch should be applied in early spring so as to
  hold in all the moisture from the winter.
  
• Soil should be wet before mulching to hold
  moisture in.
  
• In the Pacific Northwest, it is best to mulch
  after plants have had a chance to grow a bit.
  

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Colored Mulch

• Plastic mulches have long been used for their
  effects, such as weed control and temperature
  moderation. Now colored mulches.
  
• Colored mulch is becoming popular, as new
  research finds new benefits including
  
• Pest control
• Flavor enhancement
• Nutrient enhancement
• Increased yields

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Colored Mulch

• Most research of colored mulches has been done at
  the USDA-ARS Plant Research center in Florence,
  SC by plant physiologist Michael Kasperbauer.

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Colored Mulch

• The reason different colored mulches affect
  plants in different ways is that they differ in
  their light wave reflections.
  
• The phytochrome protein is an enzyme that is very
  receptive to surrounding color, and has an effect
  on where carbon is partitioned to in plants.
  
• Phytochrome acts as a competitive tool for
  plants. When other plants are close by, plants
  sense the presence because of what light rays
  they receive.

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Colored Mulch Studies

• Kasperbauer and Hunt studied the effects of
  far-red light reflecting plastic on
  tomato plants at the Florence lab with the
  following findings
• -Yield enhanced by 20 to 50 percent per season,
  depending on weather.
  
• Kasperbauer and George Antonious studied the
  effect of colored mulch on flavor -Blue mulch
  gave root vegetables a sharp taste while green
  mulch made the same varieties taste almost
  sweet.
• Kastperbauer and nematologist Bruce Fortnum
  studied the effect of colored mulch on pest
  control, specifically parasitic nematodes. The
  scientists planted tomatoes in rows mulched with
  red and black plastic, and inoculated half of
  each row with 100,000 nematode eggs.
• -Plants mulched with red plastic and infected
  with parasites yielded 85 the amount that
  nematode-free plants did.
  
• -Plants mulched with black plastic, infected with
  nematodes yielded only 50 the amount as those
  with no nematodes.
  
• Michael Orzolek of Penn. State University also
  studied the effects of colored mulch on pest
  populations, reporting that we find the lowest
  populations of insects in plants mulched with
  blue and the highest populations in rows mulched
  with yellow plastic.
• For more information go to www.ars.usda.gov and
  do a search for colored mulch.
  

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Colored Mulch Problems

• Though new colored mulch studies seem to hold
  promise for new opportunities for farmers (yield
  enhancement, pest control, and weed control), its
  still PLASTIC a non-renewable input.
• The new colored mulches are more expensive than
  most organic mulches because there are patents
  for the special far-red reflecting plastics.
  
• Plastic doesnt renew the soil nutrients and
  biomass like organic mulches do.
  
• Studies have shown that organic mulches with a
  depth of 5 cm or greater conserve soil moisture
  better than plastic mulch.
  

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Mulch for the Home Garden/Small Farm

• On small scale farming operations, the home
  gardening, hand-applied mulching techniques can
  be effective for suppressing weed growth,
  renewing soil nutrients, conserving soil
  moisture, etc. and therefore labor. Plastic
  mulches are a big non-renewable input, especially
  when used on large scale.
• On larger scale farms, hand-applied mulches are
  less labor-saving, since the mulch has to be
  applied so widely.
  
• Therefore, other techniques are better for large
  farms.

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Large Farm Mulching Techniques

• Types
• Living mulch
• Slash/mulch
• Conservation-tillage or crop residue management
  techniques

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Living Mulch

• Living mulch is a cover crop that is
  inter-planted with the primary crop(s) during the
  growing season.
  
• Living mulches are also referred to as green
  manures, smother crops, or simply cover crops
  depending on how they are managed and what their
  function is.

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Living mulch

• Functions
• Weed suppression-labor reduction
• Erosion reduction
• Temperature moderation
• Diversification
• Pest control
• Allelopathic properties

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Studies

• In India, Shetty and Rao (1981) studied the
  affect of smother crops of cowpea and mungbean on
  sorghum and pigeonpea crops and found the smother
  crops to reduce the need to hand weed by half,
  without compromising yield.

In the Methow Valley farmer Sam Lucy has been
experimenting with the use of rye, red clover,
and buckwheat as a way to eradicate weeds from
his land. So far, hes had positive results and
has been able to turn formerly weedy pasture land
to crops without using herbicides or large
amounts of labor.
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Living Mulch Cautions

• Living mulches can compete for soil water and
  nutrients if they are poorly selected for a
  specific area.
  
• It is important to plant cover crops that are not
  prone to the same diseases or pest problems as
  the main crop.
  
• Cover crops should be selected to balance soil
  nutrients. Example mungbeans add nitrogen to
  soil where sorghum crop needs it.
  
• Cover crops should be selected to harbor
  crop-friendly insect species.

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Living mulch Is it beneficial in all locations?

• Since a living mulch does need some water, it may
  be too competitive with crop species in some dry
  locals.
  
• Plant pathology H. David Thurston explains that
  more research is needed in order to find annual
  cover crops that are appropriately adapted to
  climates that receive little precipitation.
• In dry locals living mulch is more effective as a
  smother crop or cover for a fallow period than as
  a living mulch.
  

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Slash/Mulch Systems

• Thurston explains that slash/mulch systems are an
  indigenous technique that was developed in
  substitution to slash-and-burn systems in parts
  of the tropics where humidity made burning
  impossible.
• Seeds are broadcast into vegetation after a 2
  year fallow period, and the vegetation is then
  cut, moved around some, and left to act as mulch
  for germinating seeds.
• Practice and knowledge of the special techniques
  used to broadcast the seeds are necessary, and
  often the elders are the ones who do that job.
  
• Very old systems- have been around over 500 years
  and were documented by early Spanish explorers of
  Latin America.

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Slash/Mulch Systems

• Functions
• Weed suppression-labor reduction
• Regulation of microclimate of crops
• Nutrient cycling
• Erosion control
• Soil erosion is one of the biggest agricultural
  problems in many parts of the developing world
  as well as the industrialized world.
  
• More and more farmers are turning to mulch for
  erosion control benefits.
  

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Mulch and Erosion Control
Researcher R. Lal explains that mulch reduces
soil erosion by preventing surface sealing from
raindrop impact on the soil and by enhancing
biological activity that leads to the development
of macropores in the soil. In his 1977 study on s
oil erosion in the tropics of Africa, Lal found
that soil loss wasnt significantly increased
when slope steepness increased from 1 to 15
with mulch rates of 4 to 6 tons of straw per
hectare.
The study in Africa showed an inverse
relationship between mulch and erosion rates.
(SEE TABLE)
Greenland and Lal Table 4. 9
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Other Systems

• In Beltsville, Maryland at the USDA-ARS Research
  Center, plant physiologists Abdul-Baki and
  Treasdale (1997) studied the use of hairy vetch
  in a system similar to slash/mulch.
• Vetch was planted as a cover crop, and then cut,
  and tomato plants were planted into the mulch.
  
• Findings
• 85 of maximum yields were produced without
  the use of commercial nitrogen.
  
• Between 1991-1996 a mean of 8.4 tons per acre
  more tomatoes were produced with the vetch system
  when compared to crops mulched with black
  plastic, and 10.4 tons per acre more than crops
  grown in bare soil.
• When inputs and outputs were calculated, crops
  mulched with hairy vetch increased net profits by
  3,900 per acre on average over the six year
  study.

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Drawbacks of Slash/Mulch type systems

• The cover crop (mulch-to-be) needs lots of water,
  and therefore is best suited for environments
  that get plenty of rainfall.
  
• Requires long fallow period.
• Conservation tillage techniques may be more
  viable for drier environments.

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Conservation Tillage

• Soil scientist Paul Unger defines conservation
  tillage as an umbrella term covering various
  types of tillage designed to retain crop residues
  on the soil surface.
• At least 30 of residue must be left on the
  surface after planting to be considered
  conservation tillage.

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Conservation Tillage

• Functions
• Erosion control
• Soil moisture retention
• Increased mycorrhizae fungi activity
• Increased yields
• Decreased inputs
• Less tractor fuel
• Less chemical fertilizers

No-till Drill
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Conservation Tillage Studies

• USDA-ARS researchers studied crop residues in the
  Corn Belt region and found
  
• For every ton of crop residue per acre left on
  the surface, 65 less soil is lost from erosion
  
• Unger studied the effect of wheat residues on the
  following years sorghum yield and found
  
• Approximately 2 Mg/ha greater grain yield
• Residue levels of 8 to 10 mg/ha conserved 80 to
  90mm more water at planting of next years crop.
  

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Conservation Tillage Cautions

• Techniques have to be developed site-specifically
  to be the most effective in controlling erosion
  and runoff.
  
• In some places, some tillage is actually
  beneficial.
  
• In certain situations no-till systems can harbor
  pests. (Not all fungus is good fungus)
  
• These techniques have more positive effects where
  crops are rotated. (Pest control)
  

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Conclusion

• For every place, there is a mulch and for every
  mulch there is a place.

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References and Resources

• Abdul-Baki, A.A. Treasdale, J. R. (1997).
  Sustainable production of fresh-market tomatoes
  and other summer vegetables with organic mulches.
  (US Department of Agriculture and Agricultural
  Research Service Bulletin No. 2279).
• Adams, S. (Oct. 1997). Colored mulch starves
  nematodes. Agricultural Research 45(10).
  Academic Search Elite, 2 pp.
  
• Altieri, M. A. Liebman, M. (1988). Weed
  management in agroecosystems ecological
  aproaches. Boca Raton CRC Press.
  
• Davies, J.W. (1975). Mulching effects on plant
  climate and yield. Geneva World Meteorological
  Organization.
  
• Gliessman, S R. (2000). Agroecology Ecological
  processes in sustainable agriculture. Boca
  Raton CRC Press LLC.
  
• Greenland, D.J. Lal, R. (Eds.). (1997). Soil
  conservation and management in the humid tropics.
  New York John Wiley Sons.
  
• Jalota, S.K Prihar, S.S. (1998). Reducing
  Soil Water Evaporation With Tillage and
  Straw Mulching. Ames Iowa State University
  Press.
• Liebman, M., Mohler, C.L., Staver, C.P.
  (2001). Ecological management of agricultural
  weeds. Cambridge Cambridge University Press.
  
• Pons, L. (Sept.2003). More than meets the eye
  New findings on how color can affect food plants.
  Agricultural Research 51(9), 14-16.
  
• Raloff, J. (Feb.1998). Colored mulch improves a
  green thumb. Consumer Research Magazine 81(2).
  Academic Search Elite, 4 pp.
  
• Rodale, R. Olds, J., (Eds.). (1972). The
  organic way to mulching. Emmaus Rodale Press,
  Inc.
  
• Rosemeyer, M. (2000). Improving agroecosystem
  sustainability using organic (plant-based) mulch.
  In Gliessman, S.R. (2001). Agroecosystem
  sustainability Developing practical strategies.
  (pp. 67-85). Boca Raton CRC Press LLC.
• Thurston, H.D. (1997). Slash/Mulch Systems
  Sustainable methods for tropical agriculture.
  Boulder Westview Press.
  
• Unger, P.W. (1994). Managing agricultural
  residues. Boca Raton CRC Press, Inc.
  
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