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Tuesday, April 28, 2015


1.    Companion Planting
In the simplest terms, companion planting is the technique of combining two plants for a particular purpose. If your crops are regularly attacked by insects, you can use companions to hide, repel, or trap pests. Other companions provide food and shelter to attract and protect beneficial insects. And some plants grow well together just because they don’t compete for light or rooting space. Expanding the diversity of your garden plantings and incorporating plants with particularly useful characteristics are both part of successful companion planting.
Companion Planting is ideal for organic gardening because in nature, where plants grow without cultivation, there is always a mixture of plant types growing in an area. The selection of the plants living in an area depends on the soil type, local climactic conditions, and horticultural history. With few exceptions, the plants that grow together in the wild are mutually beneficial in that they allow for maximum utilization of light, moisture and soil. Plants needing less light live in the shade of those which must have full light, while the roots of some plants live close to the surface and others send their roots far down into the ground. This is known as companion planting. Companion planting enables gardeners to make maximum use of sun, soil and moisture to grow mixed crops in one area.
Beneficial effects of Companion Planting is Some plants have a beneficial effect upon the garden because of some peculiar characteristic of their growth, scent, or root formation and soil demands. Odoriferous plants (the smelly ones), including those with aromatic oils, play an important part in determining just which insects visit the garden. Hemp, for instance, is said to repel the cabbage butterfly. But while some plants can repel insects, they can also hinder the growth rate of other plants or otherwise adversely affect them. Below are combinations of
vegetables, herbs, flowers and weeds that are mutually beneficial, according to reports of organic gardeners and companion planting guides.
2.    Crop Rotation
Crop rotation is an easy way to control diseases and insects at no cost. For example, tomatoes, cauliflower or cabbage planted in the same location each year will actually encourage buildup of certain diseases in the soil. By rotating crops, you are removing the host plant and preventing the spread of disease. Also, as overwintering insects emerge from the soil in the spring, they expect to find the same plant in the same place. By moving garden plants around, insect pests will have a harder time finding their target.
Each crop has different fertilizer requirements. By changing the location of your crops you can avoid the risk of depleting the soil of specific nutrients. Some crops will actually add essential elements to the soil. By using crop rotation, you can actually build up the soil over the years.
Plants are often grouped by families that share similar growth habits and cultural requirements. By knowing your plant families (and their garden companions) you can create a plan for your own garden rotation. The following example divides the garden into four sections. As you can see, each year, the vegetable groups are planted in a different section of the garden.
3.    Countor Ploughing
Contour plowing (or contour ploughing) or contour farming is the farming practice of plowing across a slope following its elevation contour lines. The rows form slow water run-off during rainstorms to prevent soil erosion and allow the water time to settle into the soil. In contour plowing, the ruts made by the plow run perpendicular rather than parallel to slopes, generally resulting in furrows that curve around the land and are level. A similar practice is contour bunding where stones are placed around the contours of slopes.
Contour ploughing is a well-established agronomic measure that contributes to soil and water conservation . The soil is ploughed along the contour instead of up- and downward. This decreases the velocity of runoff and thus soil erosion by concentrating water in the downward furrows. Contour ploughing on the other hand purposely builds a barrier against rainwater runoff which is collected in the furrows. Infiltration rates increase and more water is kept in place. Contour ploughing is especially important at the beginning of the rainy season when biological conservation effects are poor. The effectiveness of contour ploughing decreases with increase in slope gradient and length, rainfall intensity and erodibility of the soil (http://www.geo.fu-berlin.de).
4.    Biological Pest Control
Biological control is the deliberate use of one organism to regulate the population size of a pest organism. There are three main branches of biological control. Classical biological control is the control of pests introduced from another region through importing specialized natural enemies of the pest from its native range. The aim is to establish a sustained population of the natural enemies. Conservation biological control aims to manipulate the environment to favor natural enemies of the pest. Pedro Barbosa (University of Maryland) has written and excellent book on the topic.
Augmentation biological control occurs when the number of biolotical control agents is supplemented. Inoculation is the introduction of a small number of individuals of the biological control agent, while inundation is the introduction of vast numbers of individuals. This over all approach is common when the biological control agent can not survive the entire year, or can not achieve densities high enough to regulate the pest population.
The benefits of biological control are that it can provide fairly permanant regulation of devastating agricultural and environmental pests that may be difficult or impossible to manage with more traditional chemical means. However, there are obvious risks. Biological control agents may negatively affect native species directly or indirectly. Historically biological control introductions were not regulated the way they are today, and some horrible mistakes were made in the name of biological control (e.g. cane toads in Australia). Even relatively specialized herbivorous insects released for the biological control of invasive weeds can pose risk to related native plants.
The risks inherent to biological control have led to a strong backlash against it. Where once it was touted as the “environmentally safe” way to control pests without toxic chemicals, it is now reviled as being a cure worse than the disease. I feel that neither polemical perspective has merit. Biological control is both powerful and risky. With caution and study, safe, effective biological control should be possible. We simply need to take the time necessary to do the appropriate research prior to considering an introduction, and to weigh the pros and cons very carefully (http://lamar.colostate.edu).
5.    Irrigation
Irrigation is the artificial application of water to the land or soil. It is used to assist in the growing of agricultural crops, maintenance of landscapes, and revegetation of disturbed soils in dry areas and during periods of inadequate rainfall. Additionally, irrigation also has a few other uses in crop production, which include protecting plants against frost, suppressing weed growing in grain fields and helping in preventing soil consolidation. In contrast, agriculture that relies only on direct rainfall is referred to as rain-fed or dryland farming. Irrigation systems are also used for dust suppression, disposal of sewage, and in mining. Irrigation is often studied together with drainage, which is the natural or artificial removal of surface and sub-surface water from a given area (http://en.wikipedia.org).
There are three broad classes of irrigation systems: (1) pressurized distribution; (2) gravity flow distribution; and (3) drainage flow distribution. The pressurized systems include sprinkler, trickle, and the array of similar systems in which water is conveyed to and distributed over the farmland through pressurized pipe networks. There are many individual system configurations identified by unique features (centre-pivot sprinkler systems). Gravity flow systems convey and distribute water at the field level by a free surface, overland flow regime. These surface irrigation methods are also subdivided according to configuration and operational characteristics. Irrigation by control of the drainage system, subirrigation, is not common but is interesting conceptually. Relatively large volumes of applied irrigation water percolate through the root zone and become a drainage or groundwater flow. By controlling the flow at critical points, it is possible to raise the level of the groundwater to within reach of the crop roots. These individual irrigation systems have a variety of advantages and particular applications which are beyond the scope of this paper. Suffice it to say that one should be familiar with each in order to satisfy best the needs of irrigation projects likely to be of interest during their formulation.
Irrigation systems are often designed to maximize efficiencies and minimize labour and capital requirements. The most effective management practices are dependent on the type of irrigation system and its design. For example, management can be influenced by the use of automation, the control of or the capture and reuse of runoff, field soil and topographical variations and the existence and location of flow measurement and water control structures. Questions that are common to all irrigation systems are when to irrigate, how much to apply, and can the efficiency be improved. A large number of considerations must be taken into account in the selection of an irrigation system. These will vary from location to location, crop to crop, year to year, and farmer to farmer. In general these considerations will include the compatibility of the system with other farm operations, economic feasibility, topographic and soil properties, crop characteristics, and social constraints (http://www.fao.org).
a.    Compatibility
The irrigation system for a field or a farm must function alongside other farm operations such as land preparation, cultivation, and harvesting. The use of the large mechanized equipment requires longer and wider fields. The irrigation systems must not interfere with these operations and may need to be portable or function primarily outside the crop boundaries (i.e. surface irrigation systems). Smaller equipment or animal-powered cultivating equipment is more suitable for small fields and more permanent irrigation facilities.
b.    Economics
The type of irrigation system selected is an important economic decision. Some types of pressurized systems have high capital and operating costs but may utilize minimal labour and conserve water. Their use tends toward high value cropping patterns. Other systems are relatively less expensive to construct and operate but have high labour requirements. Some systems are limited by the type of soil or the topography found on a field. The costs of maintenance and expected life of the rehabilitation along with an array of annual costs like energy, water, depreciation, land preparation, maintenance, labour and taxes should be included in the selection of an irrigation system.
c.    Topographical characteristics
Topography is a major factor affecting irrigation, particularly surface irrigation. Of general concern are the location and elevation of the water supply relative to the field boundaries, the area and configuration of the fields, and access by roads, utility lines (gas, electricity, water, etc.), and migrating herds whether wild or domestic. Field slope and its uniformity are two of the most important topographical factors. Surface systems, for instance, require uniform grades in the 0-5 percent range
d.   Soils
The soil’s moisture-holding capacity, intake rate and depth are the principal criteria affecting the type of system selected. Sandy soils typically have high intake rates and low soil moisture storage capacities and may require an entirely different irrigation strategy than the deep clay soil with low infiltration rates but high moisture-storage capacities. Sandy soil requires more frequent, smaller applications of water whereas clay soils can be irrigated less frequently and to a larger depth. Other important soil properties influence the type of irrigation system to use. The physical, biological and chemical interactions of soil and water influence the hydraulic characteristics and filth. The mix of silt in a soil influences crusting and erodibility and should be considered in each design. The soil influences crusting and erodibility and should be considered in each design. The distribution of soils may vary widely over a field and may be an important limitation on some methods of applying irrigation water.
e.    Water supply
The quality and quantity of the source of water can have a significant impact on the irrigation practices. Crop water demands are continuous during the growing season. The soil moisture reservoir transforms this continuous demand into a periodic one which the irrigation system can service. A water supply with a relatively small discharge is best utilized in an irrigation system which incorporates frequent applications. The depths applied per irrigation would tend to be smaller under these systems than under systems having a large discharge which is available less frequently. The quality of water affects decisions similarly. Salinity is generally the most significant problem but other elements like boron or selenium can be important. A poor quality water supply must be utilized more frequently and in larger amounts than one of good quality.
f.     Crops
The yields of many crops may be as much affected by how water is applied as the quantity delivered. Irrigation systems create different environmental conditions such as humidity, temperature, and soil aeration. They affect the plant differently by wetting different parts of the plant thereby introducing various undesirable consequences like leaf burn, fruit spotting and deformation, crown rot, etc. Rice, on the other hand, thrives under ponded conditions. Some crops have high economic value and allow the application of more capital-intensive practices. Deep-rooted crops are more amenable to low-frequency, high-application rate systems than shallow-rooted crops.
g.    Social influences
Beyond the confines of the individual field, irrigation is a community enterprise. Individuals, groups of individuals, and often the state must join together to construct, operate and maintain the irrigation system as a whole. Within a typical irrigation system there are three levels of community organization. There is the individual or small informal group of individuals participating in the system at the field and tertiary level of conveyance and distribution. There are the farmer collectives which form in structures as simple as informal organizations or as complex as irrigation districts. These assume, in addition to operation and maintenance, responsibility for allocation and conflict resolution. And then there is the state organization responsible for the water distribution and use at the project level.
Irrigation system designers should be aware that perhaps the most important goal of the irrigation community at all levels is the assurance of equity among its members. Thus the operation, if not always the structure, of the irrigation system will tend to mirror the community view of sharing and allocation.
Irrigation often means a technological intervention in the agricultural system even if irrigation has been practiced locally for generations. New technologies mean new operation and maintenance practices. If the community is not sufficiently adaptable to change, some irrigation systems will not succeed.
h.    External influences
Conditions outside the sphere of agriculture affect and even dictate the type of system selected. For example, national policies regarding foreign exchange, strengthening specific sectors of the local economy, or sufficiency in particular industries may lead to specific irrigation systems being utilized. Key components in the manufacture or importation of system elements may not be available or cannot be efficiently serviced. Since many irrigation projects are financed by outside donors and lenders, specific system configurations may be precluded because of international policies and attitudes.

DFID (2004). The Impact of Climate Change on Pro-Poor Growth. DFID: London, UK.

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