Cover Crops can be effective on Farms or Orchards for Soil Reconditioning, Pest Protection & Other Reasons

There are some advantages for employing the use of cover crops in agriculture. Cover crops used to recondition soil are one of the primary reasons for its implementation. These types of crops enhance soil structure, moisture content, promotes soil nutrition and helps to prevent soil erosion as well. These properties are imparted to the soil when the crop is used as a mulch. This usually happens when the crop is mowed or harvested and the residual is left as fallow afterwards. In essence, cover crops can serve as a type of 'rotation crop' when the extended use of a primary crop tends to have the effect of depleting nutrients or soil condition. These soil properties can be restored through the use of cover crops. The soil reconditioning process happens as the crop is plowed and a certain amount is left on the ground to become a mulch later on. Cover crops are seeded varieties such as clover or various grass types. It is recommended that a dense cover crop be used to establish a mulch for the above stated reasons. In addition, a dense cover crop can also prevent the outgrowth of weeds. If the crop is dense enough, it could also serve as an energy crop such as those used to help produce biofuel or bioelectricity. For example, the use of Anaerobic Digestors could be a viable way to produce combined heat and power (CHP) on farms using cover crops such as grasses. The biogas made from an anaerobic digestor can serve as a natural gas source that can be used for either boilers or generators for either electricity, heat or both. The effectiveness of a cover crop can be related to how dense or thick it becomes.

Two measureable indicators of crop density are crop height and amount of ground cover (percent vegetation cover).In a past study used on vineyards, over 30 types of different cover crops were measured for their plant height and vegetation cover.The results of the study showed that around half of the crops had plant heights from 18 - 36 inches and many also had at least 70 % vegetation cover [ 1. Bugg 1996 ]. Cover crops also have the possible use in home gardening. The ability to convert cover crops into mulch material can be applied later on as a compost for the garden. The crop can also be used directly to improve soil conditions due to a variety of reasons. These plants promote the deposition of carbohydrate compounds near the roots from microorganisms, the roots also form an underground network the may allow for future plants to follow known as biodrilling [ 2. Pleasant 2009 ]. The use of cover crops also serves the purpose of pest protection, especially for citrus orchard, nut or vineyard crops. For example, the use of cover crops were employed
for the control of aphids that were comprimising specific pecan orchards. Many aphids in these types of orchards are resistant to insecticides to a specific type of cover crop was grown to help halt the growth of aphids by providing a habitat for ladybugs that feed on aphids [ 3. Bugg et al 1993 ]. Cover crops may not always be effective in eliminating pests, due to various factors that are not as controllable or if the crop is mismanaged. Overall, cover crops can be utilized by various types of farms, orchards or home gardening, which may be able to serve several functions at one time such as soil nutrition, prevent erosion, become an energy crop, and control weeds or insect pests.

REFERENCES

1. "Comparison of 32 Cover Crops in an Organic Vineyard on the North Coast of California", Biological Agriculture and Horticulture Vol 13 pgs 63-81 [1996] by R. Bugg, G. McGourty, M. Sarrantonio, W.T. Lanini, R. Bartolucci

2. "Cover Crops: Options, Tips and Advantages for the Home Garden" - Mother Earth News - Oct/Nov 2009 by Barbara Pleasant

3. "Sesbania exaltata Cory as a Warm Season Cover Crop in Pecan Orchards: Effects on Aphidophagous Coccinellidae and Pecan Aphids", Biological Agriculture and Horticulture Vol 9 pgs 215-229 by R. Bugg and J. Dutcher

Photos taken from the Picasa Web Album

KEYWORDS: Natural Pest Protection, Cover Crops for Vineyards & Citrus Orchards, Cover Crop Density and Height, Rotation Crops, Fallow, Reconditioning Soil, Cover Crops for Bioenergy, Preventing Soil Erosion, Mulches, Composts, Soil Nutrition, Grass & Clover Cover Crop Plants, Natural Weed Control

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Biofuel vs Bioelectricity : Grasses mostly used for Biofuel Production, Bioelectricity for Biorefineries and Possible CHP on Farms

It is estimated that millions of acres will be set aside for the purpose of growing energy crops such as switchgrass in future years. Debates are common as to whether it would be more efficient to use switchgrass to produce electrical power (bioelectricity) versus it's use in producing cellulosic based ethanol for vehicles. Several factors should determine the use of grasses for bioenergy purposes. One of the most important factors, which many scientists agree upon, is the location of the bioenergy farms in relation to the nearest Biomass Conversion Facility (BCM). In fact the USDA offers a Biomass Crop Assistance Program for farmers that intend to grow, harvest, collect and transport bioenergy crops to selected BCM's. The more common Biomass Conversion Facilities most likely will be ethanol biorefineries. Since many BCM's will have a large manufacturing capability, the most common application for bioelectrical power - should be for biorefineries. Thermochemical manufacturing processes common to an Integrated Biorefinery should allow for ample sized power plants to be built along with the refinery, which would also use biomass (ie grass) as a (shared) power source. If the biorefinery is large enough, it may produce ample amounts of electrical power. For example, a Biomass operated Integrated Gasification Combined Cycle (BIGCC) power plant that can produce at least 100 MW of electrical power can also provide additional heating needs for ethanol processing and also put back a net of around 20 MW of electricity back into the power grid for an estimated 40 million gallon per year ethanol capacity manufacturing plant [1. De Kam et al 2009].

Switchgrass also has the potential to produce an array of different chemicals, other than ethanol, such as mixed alcohols and organic acids. This allows different types of biorefineries to coexist using the same biomass source. The manufacture of these kinds of chemicals also allow for the production of hydrogen which would be used to make electrical fuel cell power. A power plant such as an IGCC is designed to operate on a number of different fossil fuel and/or biomass sources. In the near future, ethanol biorefineries based on corn should be retrofitted to allow the production of cellulosic ethanol from grasses. A larger amount of ethanol should be produced from switchgrass versus corn or sugarcane in the USA. Several years ago a DOE study determined that ethanol made from grasses are more efficient to produce than using corn and should produce enough ethanol to help satisfy vehicle fuel demand. This is no small task, since it is estimated that 1 ton of grass produces around 80 gallons of ethanol. It was then estimated that 30 % of petroleum used for gasoline could be displaced at 2004 consumption levels if there were around 600 cellulosic ethanol biorefineries that produced around 100 million gallons of ethanol per year [2. Houghton, Weatherwax & Ferrell 2005] -- (Link to Publication). In summary, grasses most likely will be used to produce electrical power and biofuels/chemicals simultaneously. Switchgrass could also be used on local farms to help produce further electrical power and biogas. The use of Anaerobic Digesters are commonly used in farms in Europe and are significant in use since they are another source of natural gas that can be used for Combined Heating and electrical Power (CHP). In 2007, 6 million tons of oil equivalents (called Mtoe) - as related to overall power generation, was produced from biogas in Europe with Germany being the largest energy biogas producer with the thousands of farms implementing biogas digester units [3. Weiland 2010].

REFERENCES

1. "Biomass Integrated Gasification Combined Cycle for Heat and Power at Ethanol Plants", Energy Conversion and Management vol 50 no 7 pg 1682-1690 [2009], De Kam MJ, Morey RV, Tiffany DG

2. "Breaking the Biological Barriers to Cellulosic Ethanol : A Joint Research Agenda - A Research Roadmap from the Biomass to Biofuels Workshop Sponsored by the US Department of Energy", Office of Energy Efficiency and Renewable Energy, Office of the Biomass Program, December 7-9 2005, Houghton J., Weatherwax S., Ferrell J.

3. "Biogas Production : Current State and Perspectives", Applied Microbiology and Biotechnology Vol 85 pgs 849-860 [2010], Weiland P.

Photos taken from NREL (Department of Energy) Photographic Information Exchange Archive

KEYWORDS: Cellulosic Ethanol, Anaerobic Digerstors, Integrated Gasification Combined Cycle Power Plants, Biogasifiers, Biorefineries, Biomass Conversion Facilities, Biogas, Power Cogeneration, Switchgrass, Petroleum Displacement

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