Green manure

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Green manure plants
Green manure crop - geograph.org.uk - 494809.jpg
A field of clover, a green manure crop

In agriculture, a green manure is a crop specifically cultivated to be incorporated into the soil while still green. [1] Typically, the green manure's biomass is incorporated with a plow or disk, as is often done with (brown) manure. The primary goal is to add organic matter to the soil for its benefits. Green manuring is often used with legume crops to add nitrogen to the soil for following crops, especially in organic farming, but is also used in conventional farming. [2]

Contents

Method of application

Farmers apply green manure by blending available plant discards into the soil. [3] Farmers begin the process of green manuring by growing legumes or collecting tree/shrub clippings. Harvesters gather the green manure crops and mix the plant material into the soil. The un-decomposed plants prepare the ground for cash crops by slowly releasing nutrients like nitrogen into the soil. [3]

Farmers may decide to add the green manure into the soil before or after cash crop planting. This variety in planting schedules can be seen in rice farming. [4]

Functions

Nitrogen Fixation by Green Manure Legumes Nitrogen fixation Fabaceae en.svg
Nitrogen Fixation by Green Manure Legumes

Green manures usually perform multiple functions that include soil improvement and soil protection:

Depending on the species of cover crop grown, the amount of nitrogen released into the soil lies between 40 and 200 pounds per acre. With green manure use, the amount of nitrogen that is available to the succeeding crop is usually in the range of 40-60% of the total amount of nitrogen that is contained within the green manure crop. [5]
Average biomass and nitrogen yields of several legumes [1]
CropBiomass (tons acre−1)N (lbs acre−1)
Sweet clover 1.75120
Berseem clover 1.1070
Crimson clover 1.40100
Hairy vetch 1.75110
The increased percentage of organic matter (biomass) improves water infiltration and retention, aeration, and other soil characteristics. The soil is more easily turned or tilled than non-aggregated soil. Further aeration of the soil results from the ability of the root systems of many green manure crops to efficiently penetrate compact soils. The amount of humus found in the soil also increases with higher rates of decomposition, which is beneficial for the growth of the crop succeeding the green manure crop. Non-leguminous crops are primarily used to increase biomass.

Incorporation of green manures into a farming system can drastically reduce the need for additional products such as supplemental fertilizers and pesticides.

Limitations to consider in the use of green manure are time, energy, and resources (monetary and natural) required to successfully grow and utilize these cover crops. Consequently, it is important to choose green manure crops based on the growing region and annual precipitation amounts to ensure efficient growth and use of the cover crop(s).

Nutrient release

Green manure is broken down into plant nutrient components by heterotrophic bacteria that consumes organic matter. Warmth and moisture contribute to this process, similar to creating compost fertilizer. The plant matter releases large amounts of carbon dioxide and weak acids that react with insoluble soil minerals to release beneficial nutrients. Soils that are high in calcium minerals, for example, can be given green manure to generate a higher phosphate content in the soil, which in turn acts as a fertilizer. [6]

The ratio of carbon to nitrogen in a plant is a crucial factor to consider, since it will impact the nutrient content of the soil and may starve a crop of nitrogen, if the incorrect plants are used to make green manure. The ratio of carbon to nitrogen will differ from species to species, and depending upon the age of the plant. The ratio is referred to as C:N. The value of N is always one, whereas the value of carbon or carbohydrates is expressed in a value of about 10 up to 90; the ratio must be less than 30:1 to prevent the manure bacteria from depleting existing nitrogen in the soil. Rhizobium are soil organisms that interact with green manure to retain atmospheric nitrogen in the soil. [9] Legumes, such as beans, alfalfa, clover and lupines, have root systems rich in rhizobium, often making them the preferred source of green manure material.[ citation needed ]

Crops

Many green manures are planted in autumn or winter to cover the ground before spring or summer sowing. [10]

  1. 1 2 3 4 5 6 7 8 This is one of many legumes that may be used as a green manure crop. [5]
  2. 1 2 3 This is one of many non-legumes that may be used as a green manure crop. [5]

History

Green manures have been used since ancient times. Farmers could only use organic fertilizers before the invention of chemical nitrogen fertilizer. There is evidence for the Greeks plowing broad beans and faba beans into the soil around 300 B.C. The Romans also used green manures like faba beans and lupines to make their soil more fertile. [3] Chinese agricultural texts dating back hundreds of years refer to the importance of grasses and weeds in providing nutrients for farm soil. It was also known to early North American colonists arriving from Europe. Common colonial green manure crops were rye, buckwheat and oats. [6]

Traditionally, the incorporation of green manure into the soil is known as the fallow cycle of crop rotation, which was used to allow the soil to regain its fertility after the harvest.[ citation needed ]

Limitations of green manure

Managing green manure improperly or without additional chemical inputs may limit crop production. Mixing green manures into the soil without enough time before crop planting could stop the flow of nitrogen (nitrogen immobilization). When nitrogen stops flowing there won't be enough nutrients for the next crop planting. [3] Farming systems with short growth spans for green manure are not usually efficient. Farmers must weigh the cost of green manures with their productivity to determine suitability. [4]

See also

Related Research Articles

<span class="mw-page-title-main">Compost</span> Mixture used to improve soil fertility

Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical, and biological properties. It is commonly prepared by decomposing plant and food waste, recycling organic materials, and manure. The resulting mixture is rich in plant nutrients and beneficial organisms, such as bacteria, protozoa, nematodes, and fungi. Compost improves soil fertility in gardens, landscaping, horticulture, urban agriculture, and organic farming, reducing dependency on commercial chemical fertilizers. The benefits of compost include providing nutrients to crops as fertilizer, acting as a soil conditioner, increasing the humus or humic acid contents of the soil, and introducing beneficial microbes that help to suppress pathogens in the soil and reduce soil-borne diseases.

<span class="mw-page-title-main">Crop rotation</span> Agricultural practice of changing crops

Crop rotation is the practice of growing a series of different types of crops in the same area across a sequence of growing seasons. This practice reduces the reliance of crops on one set of nutrients, pest and weed pressure, along with the probability of developing resistant pests and weeds.

<span class="mw-page-title-main">Nitrogen deficiency</span> Nutrient deficiency

Nitrogen deficiency is a deficiency of nitrogen in plants. This can occur when organic matter with high carbon content, such as sawdust, is added to soil. Soil organisms use any nitrogen available to break down carbon sources, making nitrogen unavailable to plants. This is known as "robbing" the soil of nitrogen. All vegetables apart from nitrogen fixing legumes are prone to this disorder.

<span class="mw-page-title-main">Legume</span> Plant in the family Fabaceae

Legumes are plants in the family Fabaceae, or the fruit or seeds of such plants. When used as a dry grain for human consumption, the seeds are also called pulses. Legumes are grown agriculturally, primarily for human consumption; for livestock forage and silage; and as soil-enhancing green manure. Well-known legumes include beans, soybeans, chickpeas, peanuts, lentils, lupins, grass peas, mesquite, carob, tamarind, alfalfa, and clover. Legumes produce a botanically unique type of fruit – a simple dry fruit that develops from a simple carpel and usually dehisces on two sides.

<span class="mw-page-title-main">Cover crop</span> Crop planted to manage erosion and soil quality

In agriculture, cover crops are plants that are planted to cover the soil rather than for the purpose of being harvested. Cover crops manage soil erosion, soil fertility, soil quality, water, weeds, pests, diseases, biodiversity and wildlife in an agroecosystem—an ecological system managed and shaped by humans. Cover crops can increase microbial activity in the soil, which has a positive effect on nitrogen availability, nitrogen uptake in target crops, and crop yields. Cover crops may be an off-season crop planted after harvesting the cash crop. Cover crops are nurse crops in that they increase the survival of the main crop being harvested, and are often grown over the winter. In the United States, cover cropping may cost as much as $35 per acre.

<span class="mw-page-title-main">Polyculture</span> Growing multiple crops together in agriculture

In agriculture, polyculture is the practice of growing more than one crop species together in the same place at the same time, in contrast to monoculture, which had become the dominant approach in developed countries by 1950. Traditional examples include the intercropping of the Three Sisters, namely maize, beans, and squashes, by indigenous peoples of Central and North America, the rice-fish systems of Asia, and the complex mixed cropping systems of Nigeria.

<span class="mw-page-title-main">Nutrient management</span> Management of nutrients in agriculture

Nutrient management is the science and practice directed to link soil, crop, weather, and hydrologic factors with cultural, irrigation, and soil and water conservation practices to achieve optimal nutrient use efficiency, crop yields, crop quality, and economic returns, while reducing off-site transport of nutrients (fertilizer) that may impact the environment. It involves matching a specific field soil, climate, and crop management conditions to rate, source, timing, and place of nutrient application.

<span class="mw-page-title-main">Root nodule</span> Plant part

Root nodules are found on the roots of plants, primarily legumes, that form a symbiosis with nitrogen-fixing bacteria. Under nitrogen-limiting conditions, capable plants form a symbiotic relationship with a host-specific strain of bacteria known as rhizobia. This process has evolved multiple times within the legumes, as well as in other species found within the Rosid clade. Legume crops include beans, peas, and soybeans.

<span class="mw-page-title-main">Soil fertility</span> The ability of a soil to sustain agricultural plant growth

Soil fertility refers to the ability of soil to sustain agricultural plant growth, i.e. to provide plant habitat and result in sustained and consistent yields of high quality. It also refers to the soil's ability to supply plant/crop nutrients in the right quantities and qualities over a sustained period of time. A fertile soil has the following properties:

<span class="mw-page-title-main">Soil conservation</span> Preservation of soil nutrients

Soil conservation is the prevention of loss of the topmost layer of the soil from erosion or prevention of reduced fertility caused by over usage, acidification, salinization or other chemical soil contamination.

<span class="mw-page-title-main">Organic fertilizer</span> Fertilizer developed from natural processes

Organic fertilizers are fertilizers that are naturally produced. Fertilizers are materials that can be added to soil or plants, in order to provide nutrients and sustain growth. Typical organic fertilizers include all animal waste including meat processing waste, manure, slurry, and guano; plus plant based fertilizers such as compost; and biosolids. Inorganic "organic fertilizers" include minerals and ash. The organic-mess refers to the Principles of Organic Agriculture, which determines whether a fertilizer can be used for commercial organic agriculture, not whether the fertilizer consists of organic compounds.

<span class="mw-page-title-main">Living mulch</span> Cover crop grown with a main crop as mulch

In agriculture, a living mulch is a cover crop interplanted or undersown with a main crop, and intended to serve the purposes of a mulch, such as weed suppression and regulation of soil temperature. Living mulches grow for a long time with the main crops, whereas cover crops are incorporated into the soil or killed with herbicides.

<span class="mw-page-title-main">Tropical agriculture</span>

Worldwide more human beings gain their livelihood from agriculture than any other endeavor; the majority are self-employed subsistence farmers living in the tropics. While growing food for local consumption is the core of tropical agriculture, cash crops are also included in the definition.

<span class="mw-page-title-main">Organic coffee</span>

Organic coffee is coffee produced without the aid of artificial chemical substances, such as certain additives or some pesticides and herbicides.

<span class="mw-page-title-main">Agricultural pollution</span> Type of pollution caused by agriculture

Agricultural pollution refers to biotic and abiotic byproducts of farming practices that result in contamination or degradation of the environment and surrounding ecosystems, and/or cause injury to humans and their economic interests. The pollution may come from a variety of sources, ranging from point source water pollution to more diffuse, landscape-level causes, also known as non-point source pollution and air pollution. Once in the environment these pollutants can have both direct effects in surrounding ecosystems, i.e. killing local wildlife or contaminating drinking water, and downstream effects such as dead zones caused by agricultural runoff is concentrated in large water bodies.

<span class="mw-page-title-main">Biofertilizer</span> Substance with micro-organisms

A biofertilizer is a substance which contains living micro-organisms which, when applied to seeds, plant surfaces, or soil, colonize the rhizosphere or the interior of the plant and promotes growth by increasing the supply or availability of primary nutrients to the host plant. Biofertilizers add nutrients through the natural processes of nitrogen fixation, solubilizing phosphorus, and stimulating plant growth through the synthesis of growth-promoting substances. The micro-organisms in biofertilizers restore the soil's natural nutrient cycle and build soil organic matter. Through the use of biofertilizers, healthy plants can be grown, while enhancing the sustainability and the health of the soil. Biofertilizers can be expected to reduce the use of synthetic fertilizers and pesticides, but they are not yet able to replace their use. Since they play several roles, a preferred scientific term for such beneficial bacteria is "plant-growth promoting rhizobacteria" (PGPR).

<span class="mw-page-title-main">Manure</span> Organic matter, mostly derived from animal feces, which can be used as fertilizer

Manure is organic matter that is used as organic fertilizer in agriculture. Most manure consists of animal feces; other sources include compost and green manure. Manures contribute to the fertility of soil by adding organic matter and nutrients, such as nitrogen, that are utilised by bacteria, fungi and other organisms in the soil. Higher organisms then feed on the fungi and bacteria in a chain of life that comprises the soil food web.

<span class="mw-page-title-main">Natural farming</span> Sustainable farming approach

Natural farming, also referred to as "the Fukuoka Method", "the natural way of farming", or "do-nothing farming", is an ecological farming approach established by Masanobu Fukuoka (1913–2008). Fukuoka, a Japanese farmer and philosopher, introduced the term in his 1975 book The One-Straw Revolution. The title refers not to lack of effort, but to the avoidance of manufactured inputs and equipment. Natural farming is related to fertility farming, organic farming, sustainable agriculture, agroecology, agroforestry, ecoagriculture and permaculture, but should be distinguished from biodynamic agriculture.

Among the many systems of classification of crops, commercial, agricultural, and taxonomical can be considered to be the most widely accepted agriculture classification of crops.

Korean natural farming (KNF) is an organic agricultural method that takes advantage of indigenous microorganisms (IMO) to produce rich soil that yields high output without the use of herbicides or pesticides.

References

  1. 1 2 Pieters, Adrian J (1927). Green Manuring (PDF). John Wiley & Sons, NY. Archived from the original (PDF) on 2012-02-02. Retrieved 2021-09-24.
  2. Larkin, Robert P.; Honeycutt, C. Wayne; Olanya, O. Modesto (2011-05-01). "Management of Verticillium Wilt of Potato with Disease-Suppressive Green Manures and as Affected by Previous Cropping History". Plant Disease. 95 (5): 568–576. doi:10.1094/PDIS-09-10-0670. ISSN   0191-2917. PMID   30731947.
  3. 1 2 3 4 Fageria, N. K. (2007-05-07). "Green Manuring in Crop Production". Journal of Plant Nutrition. 30 (5): 691–719. Bibcode:2007JPlaN..30..691F. doi:10.1080/01904160701289529. ISSN   0190-4167. S2CID   93807349.
  4. 1 2 Becker, M.; Ladha, J. K.; Ali, M. (1995-07-01). "Green manure technology: Potential, usage, and limitations. A case study for lowland rice". Plant and Soil. 174 (1): 181–194. Bibcode:1995PlSoi.174..181B. doi:10.1007/BF00032246. ISSN   1573-5036. S2CID   28306230.
  5. 1 2 3 4 Sullivan, Preston (July 2003). "Overview of Cover Crops and Green Manures: Fundamentals of Sustainable Agriculture". ATTRA.
  6. 1 2 3 4 Lawrence, James (1980). The Harrowsmith Reader, Volume II. Camden House Publishing Ltd. p. 145. ISBN   0920656102.
  7. Vasilakoglou, Ioannis; Dhima, Kico; Anastassopoulos, Elias; Lithourgidis, Anastasios; Gougoulias, Nikolaos; Chouliaras, Nikolaos (24 February 2011). "Oregano green manure for weed suppression in sustainable cotton and corn fields". Weed Biology and Management. 11 (1): 38–48. doi:10.1111/j.1445-6664.2011.00403.x.
  8. Larkin, Robert P.; Honeycutt, Wayne; Olanya Modesto, O. (May 2011). "Management of Verticillium Wilt of Potato with Disease-Suppressive Green Manures and as Affected by Previous Cropping History". Plant Dis. 95 (5): 568–576. doi:10.1094/PDIS-09-10-0670. eISSN   1943-7692. ISSN   0191-2917. PMID   30731947.
  9. Lawrence, James (1980). The Harrowsmith Reader, Volume II. Camden House Publishing Ltd. p. 146. ISBN   0920656102.
  10. "Maine Organic Farmers and Gardeners Association" (PDF). mofga.org. November 2007. Archived from the original (PDF) on 2015-03-21. Retrieved 2015-02-27.
  11. 1 2 "Green Manures". Royal Horticultural Society. Retrieved 18 October 2022.
  12. Philpott, Tom (2013-09-09). "One Weird Trick to Fix Farms Forever". Mother Jones. Retrieved 2014-03-14.