windbreak or shelterbelt is a plantation usually made up of one or by malj

VIEWS: 40 PAGES: 6

									    RAISING OF WINDBREAK/SHELTERBELT IN THAL TRACT
            FOR CONTAINING OF WIND EROSION
INTRODUCTION
One of the biggest problems of the Thal tract is power of wind erosion that move exposed soil,
sending it into the air in wind storms and depositing it elsewhere in cultivated fields. One of the
most feasible and practicable method to tackle this problem is to raise tree rows known as
shelterbelt as barrier against the wind.

Windbreak or Shelterbelt is a plantation usually made up of single or multiple rows of trees or
shrubs planted in such a manner as to provide shelter from the wind and to protect soil from
erosion. Eroded soils are less productive due to loss of fertility and are more prone to erosion.
Windbreaks are commonly planted around the boundaries of fields for environmental purposes.
Other benefits include saving crops from scorching winds, reducing loss of moisture in the field
by desiccating winds, providing habitat for wildlife and obtaining valuable wood products from
trees. Field shelterbelts are a part of conservation management systems that will help safeguard
the productive quality of our soils.




                                       Shelterbelt in Thal desert


Raja Attaullah Khan                                                                              1
Shelterbelts protect nearby leeward areas from troublesome winds to reduce wind erosion,
protect growing crops, improve irrigation efficiency and provide products like leaves, fuel wood,
timber etc. The heights of the tallest row greatly influence the size of the nearby area that is
protected or sheltered from wind. Shelterbelts give greater percent yield increases in arid areas
than in areas where water is not usually a problem. In arid areas windbreaks may need
supplemental water or water harvesting techniques during first 3 years for successful
establishment.




A multiple row shelterbelt has usually shrubs in the outer rows and taller trees in the interior.
Although wind speeds are reduced to a distance of 20 times the shelterbelt’s height, protection
from wind erosion is generally considered to extend to only 10 times the shelterbelt’s height. For
comprehensive protection of a field, windbreaks are placed in a series across the area (typically
spaced at intervals of 5 to 20 times the height of each windbreak), with individual windbreaks
running parallel to one another, but perpendicular to prevailing winds.



PURPOSE AND BENEFITS OF SHELTERBELTS
A shelterbelt is a barrier of trees to protect soil and crops from adverse effect of wind. It has
following purposes/benefits:-

   Reduce soil erosion from wind.




Raja Attaullah Khan                                                                             2
   Increase moisture for plant growth and improve irrigation efficiency by reducing moisture
    loss through evaporation.
   Protect fruit plants and crops from wind related damages e.g. bending, breaking, lodging and
    scorching.
   Enhancing plant growth and crop yield by modifying micro environment (moisture &
    temperature)
   Increased revenue and or reduced costs.
   Provide potential source of income for farmers (e.g. biomass, timber and non-timber
    products)
   Improve air quality by reducing and intercepting air borne dust particles.
   Enhance wildlife habitat and provide shelter.
   Provide shade and shelter for livestock.
   Beautification of Thal landscape which is otherwise quite dull.

The phenomenon is further explained as follows:-

Reg:- Reduced Soil Erosion By Wind
A field shelterbelt modifies the microclimate, mostly in its downwind vicinity. This modified
microclimate includes reduced wind speed and, therefore, reduced soil erosion. A significant
reduction of wind speed occurs downwind for a distance extending to approximately up to 20
times the height of the shelterbelt and also 3 to 5 times its height on the upwind side. It is safe to
assume that fields and plants are protected within an area 10 times the height (h) on the leeward
side and two times the height (h) on the windward side of the windbreak.




Raja Attaullah Khan                                                                                 3
               Approximate reduction of wind velocity by a single-row shelterbelt.


The shelterbelts must be planted perpendicular to the direction of the prevailing wind to provide
more complete protection.


Reg:- Increased Moisture for Crop Growth
Field shelterbelts reduce evaporation. Field shelterbelts use moisture and nutrients from a greater
depth than most annual crops. Additional moisture accumulated in the sheltered zone more than
compensates for moisture used by the shelterbelt.


Reg:- Reduced Wind Damage to Crops
Crops benefit from the reduced wind speeds in the protected zone. The plants are less likely to be
twisted/broken by the wind or sandblasted by eroding particles.


Reg:- Potential for Increased Crop Yields
Yield increases due to field shelterbelts as these maintain moderate moisture and temperature
condition for plant growth.


CHOICE OF SUITABLE SPECIES
Species must be adapted to the soils, climate and site conditions. The windbreak will be oriented
as close to perpendicular to the troublesome wind as possible. Irrigation will be needed for
shelterbelt establishment and growth where natural precipitation is too low for the species,




Raja Attaullah Khan                                                                              4
planted as windbreak. Following species of trees and shrubs can be used in Thal tract for raising
shelterbelt.


      Choice of Species and Numbers of Plants Required for Planting Field Shelterbelt

                                                         Number of plants required in
               Species      Plant to Plant distance
                                                         1000 feet length of shelterbelt

        Farash                         10 feet                          100

        Phoge                 3 feet in multiple row                    333

        Ber                            15 feet                          67

        Jand                           10 feet                          100

Sprinkler Irrigation and Shelterbelt
Where sprinkler irrigation is practiced, the windbreak shall be taller than the spray height in
order to prevent water loss due to wind. The windbreak should however not interfere with the
operation of the sprinkler irrigation system.


PLANNING
With good planning, site preparation and maintenance, field shelterbelts can play a significant
role in sustainable food production systems. Field shelterbelts are an investment in both the
future and long-term productivity of the soil. The benefits of shelterbelts are not achieved the
first few years. At first, a good deal of management is required to establish the trees. Other
variables in planning shelterbelts are height, porosity (or density) and spacing. The purpose and
function of shelterbelt will be accomplished within 5 to 10 years. A tall shelterbelt will provide
wind reduction over a greater distance than a shorter one. If protection from wind erosion is the
highest priority because soils are highly erodible, then a denser shelterbelt may be needed.


SITE PREPARATION
Moisture conservation is the major priority when preparing the planting site. The final pre-
planting application of pesticide is of utmost importance in Thal tract where termite infestation is
a serious problem.


PLANTING
Tree seedlings are highly perishable and should not be allowed to dry out. Saplings should be


Raja Attaullah Khan                                                                               5
planted about 1 cm deeper than they were growing in the nursery. If the soil is dry, the seedlings
should be watered immediately after planting. Farash and Phoge cuttings can be planted in
October to January whereas potted plant should be planted after the onset of monsoon rains.
Two-row shelterbelts usually consist of a shrub like Phoge and a taller tree like Farash and
proper space is kept between the rows.


Field shelterbelts should be continuous without any gap. Gaps can occur due to dead plants and
in such a case, wind erosion will accelerate in areas lying behind gaps in the shelterbelts. Dead or
missing trees must therefore be replaced continuously till shelterbelt is established.




OPERATION AND MAINTENANCE
Certain actions are required to insure that shelterbelt functions as intended throughout its
expected life.
   Replacement of dead trees or shrubs will be continued until the windbreak/shelterbelt is
    functional.
   Supplemental water is provided as needed.
   Inspect trees and shrubs periodically and protect from adverse impacts including insects
    especially termite, diseases or weeds.
   Shelterbelt trees and shrubs must be protected from fire and damage from livestock and
    wildlife.
   Cattle can damage and eventually kill shelterbelts. Shelterbelts in fields prone to grazing
    must be fenced. Brushwood fence of local material would be feasible and economical.
   Fire protection is necessary because grass fires can very quickly kill young shelterbelts.

Proper care of shelterbelt is important during critical period of first few years.




Raja Attaullah Khan                                                                               6

								
To top