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