- Tropical agriculture
Worldwide more human beings gain their livelihood from
agriculture than any other endeavor; the majority are self-employed subsistencefarmers living in thetropics . While growing food for local consumption is the core of tropical agriculture,Cash crop s (normally crops grown forexport ) are also included in the definition.When people discuss the tropics, it is normal to use generalized labels to group together similar tropical areas. Common terms would include the
humid -tropics (rainforests ); the arid-tropics (deserts and dry areas); ormonsoon zones (those areas that have well defined wet/dryseasons and experience monsoons). Such labeling is very useful when discussing agriculture, because what works in one area of the world, will normally work in a similar area somewhere else, even if that area is on the opposite side of the globe.Most temperate zone agricultural techniques are inappropriate for tropical areas. The second half of the 20th century saw many attempts to duplicate in the tropics
farming practices that had been successful in temperate climates. Due to differences inclimate ,soils , and patterns ofland ownership , these largely failed. When they did succeed they tended to heavily favor farmers with substantial land holdings, as a high percentage of temperate agricultural practices areeconomically "scale-based" and favor large scale production. This in turn pushed many small-scale farmers on to ever more marginal land, as the better quality land was consolidated into larger farms.Green Revolution
The "
Green Revolution " is the name given to the most successful agricultural improvement program ever undertaken in the tropics. Funded initially by theRockefeller Foundation , it aimed to improve corn,rice , and othercereal cultivators – breedingplants that would produce more grain for the same amount of effort.From that point it expanded out to improved basic farming practices, particularly for rice farmers. The growth of crop yields was such that agriculture was able to outstrip population growth — per capita production increased every year following 1950 - with
Asia leading the way. One of the more remarkable aspects of the Green Revolution is that the total cost of the program by 1990 was approximately US$100 million, less than what a singleBoeing 747 airliner costs in 2005.It can be concluded that the
green revolution was a success, with only a minor flaw: although the crops gave more yield, they were more subject to disease since this was not a primary concern in the program.In order to address this problem together with an approach to more small-scale farming crops, there is today substantial interest in creating a second Green Revolution, based on sustainable agricultural practices and geared towards (small-scale) farmers with limitedfinancial resources (who make up the bulk of farmers in thePlant propagation
Many tropical food plants are propagated by
cutting s. Seeds are necessary for plantembryos to survive the winter and other harsh conditions such asdrought . However, where the weather is normally conducive to growth year-round, it is often advantageous for plants toreproduce through means other than seeds. By bypassing the seed stage plants can greatly accelerate theirreproductive cycle . Despite this, anyone who wishes so, may still grow tropical crops (eg fruit, ...) from seed. To do so, some special seed germination techniques to germinate it more quicker may be best used.Plant defenses
A particularly good description of plant defenses can be found at [http://www.wischik.com/marcus/essay/def.html How and why do plants defend themselves?] that states in part:
:"Plants are faced with a dilemma; while they need to attract beneficial pollinators and seed dispensers, they must also minimize the damage caused by the marauding army of herbivores. Without some form of protection the trees would be stripped bare and smaller plants would be completely devastated, and because plants stand still, they cannot run away. This is as true in Amazonian rainforest as it is in Northern coniferous forest." - Marcus Wischik.
Many (tropical) plants use
toxins to protect themselves.Cassava , one of the most important tropicalfood crop s, producescyanide uponingestion if improperly processed. Other plants are high inoxalate s (the agent that bindscalcium to formkidney stone s);castor bean s are the source ofricin , one of the most powerfulpoisons in existence; and velvet beans contain 7-10%L-dopa . The list of toxic plants is long, but toxicity does not always mean a particular plant should be avoided, the knowledge needed to render toxic plants safe to use already exists in most communities.lash/mulch
The contents of a bag of commercial
fertilizer is described in terms of NPK -nitrogen (N),phosphorus (P) andpotassium (K); with nitrogen being the main component of most commercial fertilizers.Oxygen is only a small part of theair ; the largest component of air is nitrogen. Nitrogen is the main building block ofprotein ;muscle inmammals and plant tissue in plants. If you increase the nitrogen in thesoil , you significantly increase plant growth.Legumes are a group of plants that interact withbacteria (rhizobia ) in the soil to fix nitrogen from the air, and deposit the nitrogen into the soil where it is available for other plants to use. The nitrogen deposited by legumes can be readily converted into larger harvests.Green manure s are plants grown to improve the soil, suppressweed s, limiterosion , and - when legumes are used - to increase the nitrogen content of the soil. The most common type of green manure used in the tropics isVelvet bean . It produces a thickblanket ofvine s andleaves that in addition to infusing the soil with nitrogen also smother most weeds. In addition it has reasonable tolerance to drought, low soil fertility, and highlyacidic soil. Alternatives to the Velvet bean include theLablab bean , the Jack bean, and for use above 500 m altitude, theScarlet runner bean .Once the blanket is several centimeters thick, it is chopped down with a
machete , and the vines are chopped up. This produces thickmulch on top of the ground that both inhibits weed growth and adds vitalnutrients to the soil. Corn or other crops are then planted directly into this mulch.Slash/mulch is popular in southern
Mexico ,Guatemala , andHonduras ; and in recent years has gained a following in many areas of the tropics, fromBrazil to centralAfrica . Where it has been embraced it has pushed asideslash and burn agriculture, and allowed farmers to utilize the same land continuously for many years.[http://ppathw3.cals.cornell.edu/mba_project/moist/home2.html Cornell University] has taken a leading role in
research ing the effects of mulches and slash/mulch practices in the tropics.mall-scale irrigation
In most places in the tropics sufficient precipitation occurs to grow enough food to feed the
local population ; however, it many not fall in a timely orconvenient manner. Making maximum use of thewater that does fall is an ongoing challenge.Water is a particularly important issue in
dryland farming . The ability to collect and store water at a low cost and without damaging the environment, is what opens up deserts and otherarid regions to farmers. When it rains in dryland areas, the rain storms are normally heavy, and the soil unable to absorb the large amounts of rain that comes down. This leads to excessive surface run-off that needs to be captured and retained.Commercial farms growing cash crops often use irrigation techniques similar to or identical to what would be found on large scale commercial farms located in temperate regions; as an example, the Israeli drip-irrigation lines.
Water harvesting pits
One of the simplest forms of
irrigation - the farmer digsbathtub sized pits into his fields and lines them with plastic sheets to collect rainwater. Then once thedry season sets in the farmer uses the collected water to irrigate his crops. The technique is especially useful inmountainous areas, where rapidrun-off would otherwise occur.During years with normal precipitation the growing season can be increased by an extra month or more by using harvesting pits. An extra month in many places means an extra crop can be grown. For instance if the local
growing season is 5 months long, and the farmers main crop takes 3 or 4 months to grow, an extra month may be enough time to grow a secondary crop. During times of drought, what rain does fall can be collected in the pits and used to secure the farmer's main crop.Bucket drip irrigation
An irrigation system consisting of a
bucket hung from apole , with a hose coming out of the bottom, and holes punched into the hose. The bucket is filled, andgravity feeds the water to the plants. As a rule about 40liters of water per day are needed for every 100 plants, although this can vary depending upon what is being grown.Treadle pumps
The
treadle pump is a human-powered pump designed to lift water from a depth of seven meters or less. A treadle is lever device pressed by the foot to drive a machine, in this case a pump. The treadle pump can do most of the work of a motorized pump, but costs considerably less to purchase, and needs nofossil fuel as it is driven by the operators body weight andleg muscle s. It can lift five to seven cubic meters of water per hour fromwells andborehole s up to seven meters deep and can also be used to draw water fromlakes andrivers . Most treadle pumps used are oflocal manufacture , as they are simple and inexpensive to build.Standard treadle pumps are
suction pumps, and where first developed in the early 1980s inBangladesh . Most treadle pumps manufactured inAfrica arepressure treadle pumps; a modification to the original design that means water is forced out of the pump under pressure. Pressure treadle pumps are more versatile as they allow farmers to pump water uphill, or over long distances, or fill elevated tanks.Pest control
Crop rotation
Crop rotation is the cornerstonepest control in the tropics. When a single crop is planted repeatedly in the same soil,insects anddiseases that attack that crop are allowed to build up to unmanageable levels, greatly reducing the farmer’sharvest .The most basic form of crop rotation is also the simplest: never plant the same thing in the same place twice. This results in naturally breaking the cycles of
weed s, insects and diseases that attack food crops. Rotations are used to prevent or at least partially control several pests and at the same time to reduce the farmer’s reliance on chemicalpesticides . Crop rotations often are the only economically feasible method for reducing insect and diseasedamage .Crop rotation replaces a crop that is
susceptible to a serious pest with another crop that is not susceptible. Each food crop comes with its own set of pests that attack that particular crop. By planting a different crop each time, the farmer is able to starve out those pests. Often a set of three or four crops are planted on a rotating basis, ensuring that by the time the first crop is replanted, the pests that attack it are substantially reduced.Another side benefit of crop rotation is it improves the soil. Constantly growing the same crop in the same location will strip the soil of the
nutrients that particular crop requires. Rotating to a different crop will reduce the pressure placed on the soil. Or if a green manure is used as part of the rotation sequence, the soil can actually be improved.Integrated pest management
Integrated Pest Management (IPM) was developed as an alternative to the heavy use of chemical pesticides. Eliminating all insect pests requires the extensive use of chemical pesticides, which over time can become self-defeating. Farmers end up using more and more chemicals with diminishing effect as pests quickly adapt –while at the same time naturalpredator insects are eliminated from the farm. Under IPM chemicals should be a secondary line of defense, while building up the number of natural predators on a farm is the main goal. The IPM approach calls for keeping the pestpopulations below the levels at which they cause economic injury, not total eradication.IPM in its pure form is extremely complex, and beyond the ability of most farmers to manage; however, the underlying principals have gained widespread acceptance in the tropics, with most governments sponsoring IPM educational programs.
ystem of Rice Intensification and other sustainable agricultural systems
Besides
IPM , there are also completely biological systems (not using pesticides at all) which are used in the developing world, mostly theSystem of Rice Intensification andOrganic farming . In theWorld of Organic Agriculture 2007 , we can clearly see that in Oceania and Latin America, organic farming is matching the organic farming in the developed world.Major constraints
Mild winters
Winters are mild in the tropics; there is no
frost , nosnow , and noice , so the insect population flourishes year-round. In temperate areas winter eliminates most insect pests prior to the emergence of new crops, so plants coming up in the spring have a chance to take hold and grow prior to being attacked. In the tropics plants enter a world already full of hungry adult insects.Acidic soils
Soils in the humid tropics are normally highly acidic and nutrient poor;
decomposition is rapid because of high temperatures, highhumidity , and frequent heavyrains . Heavy rains, especially monsoon rains, lead to rapid nutrientleaching , andchemical weathering of the soil. Standard temperatestrategies for improving nutrient poor soil, such ascomposting , have limited application in such an environment due to rapid leaching.Aluminum is the most commonmetal found in the Earth’scrust . It is found in all soils and in all environments, from temperate to tropical. In asoluble state it is highlytoxic to plant life, as it inhibitsroot growth; however, in neutral andalkaline soils common to the temperate zones it isinsoluble and thereforeinert . Soilfertility is directly influenced by how acidic it is, as the more acidic the higher the level of aluminum toxicity; in areas where thepH drops below 5, aluminum becomes soluble and can enter into plant roots where it accumulates.Approximately a third of all tropical soils are too acidic to support traditional food crops. These highly acidic tropical soils represent the largest untapped
arable land left in the world, and therefore more productive utilization of these lands is key to expanding the worldfood supply .Winrock International states "In the humid tropics, the relative importance of acid soils is greatest in Latin America (81%), but also significant in Africa (56%) and Asia (38%)" [http://www.winrock.org/forestry/FACTPUB/AIS_web/AIS10.html] .
Traditionally on commercial farms aluminum toxicity is countered by adding lime to the soil, which neutralizes the acid and renders the aluminum inert. However, many small land holders and resource-poor farmers cannot afford lime, and instead rely on slash-and-burn agriculture. As the original plant life is burnt, the ash acts to neutralize the acidic soil and makes the area acceptable for food plants. In time acidity increases and only plants will grow, forcing the farmer to move on and clear a new area.
Soil color in humid areas is related to the level of
oxidation that has occurred in the soil, with red soil being the result ofiron oxidation, and yellow soil being the result of aluminum oxidation.alinization
Salinization occurs naturally in arid areas where not enough rain falls to wash soluble salts down and out of the root zone. Irrigation makes the situation worse, since surface water and groundwater contain more salt than rainwater does. Salt tends to build up in the soil as water is added through irrigation. As water is used by plants andevaporates from the soil surface, the salt in the waterconcentrate s in the soil. The high temperatures and low humidity in arid regions means that salinization often accompanies irrigation.Day-length sensitive plants
Some plants have a photoperiod (
photoperiodism ) requirement for a certain number of hours of daylight before they willgrow ,flower , or producefruit . Without this they will not complete theirlife-cycle and will not produce fruit and seeds. For this reason seeds brought from the temperate zones may not perform as expected, or at all in the tropics. Some plants are genetically keyed to only start producing when a certain number of hours of daylight is reached, the same number of hours as is found in their native habitat. With the shorter daylight hours experienced in the tropics, that switch never gets thrown.Logging of rainforest/tropical forests to produce food
Throughout the tropics and predominantly in
Indonesia , and certain South-East Asian Countries, a lot of forest is being cleared to produce food. Major examples are theoil palm plantations in Indonesia and thedry rice farming techniques usingslash and burn -method in Southeast Asia. This of course adds toglobal warming (as trees collect CO2 in life and release it in death) and increases the decline in biodiversity. It has been argued that although tropical crops should be grown, it should be done in regions under threat (e.g., regions at risk of desertification, salination, ...)Low economic input in Africa, constraining the export of tropical crops
In certain tropical places (predominantly the entire continent of Africa), there are very few (registered) African companies at all to sell their products trough the normal ways, let alone that they are capable of exporting products beyond their borders/continent. This phenomenon can be clearly seen if one walks into a supermarket (not a normal market, where this isn't the case) in the developing world (e.g., Africa); almost all products come from Western companies.
As such, tropical crops (vegetables, grain, fruit), although it has high value at European markets (very low production, increasing the demand and unknown products), are not sold at all (most crops) or very limited (certain tropical fruit as papaya, guave, mango, cacao by mostly Western companies and representing only a few percentages of the entire bunch of crops).
At the country of origin, predominantly at normal markets (not supermarkets), these food items are available, but only within the season and not always the crops of the entire country (rather only the ones grown locally). Of course because the demand and availability are closer together in these places, prices are lower and farmers are not capable of getting as high returns as if they would in the West.
Availability of inexpensive Western crops and food
Western food, as it is subsidized by the
EU and theUSA , is for certain products, such as chicken, cheaper than it's counterparts in the developing world. Besides the matching food products being cheaper, the availability of Western surrogates for certain food has also proven disastrous. At least in certain continents as Africa, Western surrogate foods are thought to be 'better' and more modern by African people, who thus switch from their traditional ingredients and meals to Western counterparts (see article below).This availability of inexpensive foreign food is not only damaging to the indigenous economy, but also for the
health of the people themselves (sparking obesity, heart problems, and a lack of certain vitamins and minerals). This is believed to be because certain Western food (not only hamburgers but also the main staple food) is not qualified for them (as strange as it may seem). Because of these problems, the traditional African food is again slowly being distributed within the continent (e.g. inNairobi , the TuskerSupermarket ).Pioneering crops
Pioneering crops are used in places where the land has been striped bare, and the
topsoil has been entirely lost to erosion, or wheredesertification has started. The intent is not to grow food or cash crops, but torepair and reinvigorate the soil in order to prepare the way for the later planting of food or cash crops.Nitrogen fixing plants and trees normally form the basis of such areclamation project.Hunger season
The hunger season is that period of time when all the food from the previous
harvest has been consumed, and the next harvest is still some time away. Even in normal years, many households face an annual reduction in the amount of food they have available. Typically the hunger season will coincide with the start ofplanting the new crop, or shortly thereafter. So farmers are faced with a shortage of food at the very time they are expected to perform their heaviest labor.One way of mitigating the effects of the hunger season is growing some non-seasonal crops close to the family home, such as
banana s in humid areas, or cassava where it is arid. As an example, a family that has ten banana plants producing fruit during the hunger season is unlikely to experience excessive hardship.Sweet potato ,pigeon pea , andMoringa oleifera should also be considered.Common tropical horticulture crops
*
papaya
*rubber tree
*coconut
*Banana
* Palms (mainly oil palm)Common agricultural crops
*
Cassava
*Maize (corn)
*Rice
*Sorghum
*barley
*wheat
*buckwheat
*Sweet Potato
*Taro
*millet
* yam
*tobacco
*sugar cane
*kidney beans
*soy
*tea
*cotton
*Coffee
*cocoa
*morus alba References
* [http://www.echotech.org/network/modules.php?name=AZ Amaranth to Zai Holes - Ideas for Growing Food Under Difficult Conditions]
* [http://www.winrock.org/forestry/factnet.htm Forest, Farm, and Community Tree Network]
* [http://cidicco.hn/newcidiccoenglish/index.htm International Cover Crops Clearinghouse (CIDICCO)]
* [http://ppathw3.cals.cornell.edu/mba_project/moist/home2.html Management of Organic Inputs in Soils of the Tropics (MOIST)] - Cornell University
* [http://www.mekonginfo.org/mrc_en/doclib.nsf/0/1C15891F0E9A47FEC7256604001580FC/$FILE/FULLTEXT.HTML Report on soil conservation, soil improvement and extension for the Song Da watershed and CARE projects]
* [http://www.agroforestry.net/overstory/ The Overstory]
*The Doubly Green Revolution: "Food for All in the Twenty-First Century"; by Gordon Conway, Cornell University Press (March, 1999) ISBN 0-8014-8610-6
*Two Ears of Corn: "A Guide to People-Centered Agricultural Improvement"; by Roland Bunch, World Neighbors; 3rd edition (June, 1995) ISBN 0-942716-03-5External links
* [http://www.globalhort.org/ Global Horticulture Initiative]
* [http://www.iita.org International Institute of Tropical Agriculture]
* [http://www.bioversityinternational.org/publications/Pdf/1090.pdf Benefits of traditional vegetables, over Western food]
* [http://www.ipgri.cgiar.org/Events/IFAD-NUS/pdf/Emile%20paper%20to%20the%20CBD%20on%20Nurtrition.pdf Article on the effects of Western food to Africans]
* [http://www.nap.edu/books/0309049903/html/Lost Crops of Africa: Vol 1 Grains ]
* [http://books.nap.edu/openbook.php?isbn=0309103339 Lost Crops of Africa: Vol 2 Vegetables]
* [http://www.soel.de/oekolandbau/weltweit.html Organic Farming Worldwide]
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