Components of watershed management programme and land capability classification

Components of watershed management programme
and land capability classification
13.1 Components of watershed management programme
The main components of watershed programme are:
1. Soil and water conservation
2. Water harvesting
3. Crop management and
4. Alternate land use systems
13.1.1. Soil and water conservation measures
These measures coupled with water harvesting help to improve the moisture
availability in the soil profile and surface water availability for supplemental
irrigation. Based on the nature and type of hydraulic barriers and their cost the
conservation measures in arable lands can be divided into three categories:
Permanent treatments (Hardware treatments)
Semi permanent treatments (medium software treatments) and
Temporary treatments (software treatments).
a. Permanent measures: These measures are provided for improvement of relief,
physiography and drainage features of watershed, aimed at controlling soil erosion,
regulating surface runoff and reducing peak flow rates. Bunds, terraces and
waterways are the permanent measures in watershed management project.
Waterways: both with and without vegetation- grassed waterways for safe
disposal of runoff water.
Bunds: contour bunds –Suitable for low rainfall areas (< 600 mm) and in
permeable soils having slope up to 6%.
Graded bunds – Suitable for high rainfall areas (> 600 mm) and for poor
permeable soils having 2-6% slope and for soils having crust like ,chalka soils of
Telangana region of A.P.
Terraces: Bench terracing: suitable for soils having slopes 16 to 33%. Bench
terraces reduce both slope length and degree of slope. At Ootacamund erosion
rate decreased from 39 t/ha to less than 1.0 t/ha on 25% sloping land by bench
terracing.
b. Semi permanent measures: These are usually interbund treatments where field
sizes are large in conventionally bunded area. They are adopted to minimize the
velocity of overland flow. These measures may lost for 2 to 5 years.
i. Small section / key line bunds: A small section bund may be created
across the slope at half of the vertical bund spacing, which needs to be renovated at
an interval of 2-3 years.
ii. Strip Levelling: Levelling of about 4 to 5 m strips of land above the bund
across the major land slope help in reducing the velocity of surface flow. Strip
levelling can be done by running blade harrow at an interval of 2 to 4 years.
iii. Live beds: One or two live beds of 2-3 m width on contour or on grade
also serve the purpose. The vegetation on the beds may be annual or perennial or
both.
iv. Vegetative or live barriers: One or two barriers of close growing grasses
or legumes along the bund and at mid length of slope can filter the runoff water or
slow down over land flow. Khus grass is widely recommended as vegetative barrier.
c. Temporary measures (Software treatments): These are simple treatments for
in situ moisture conservation and needs to be remade or renovation every year.
Simple practices like contour farming, compartmental bunding, broad bed and
furrows, dead furrows, tillage and mulching have gained wide acceptance in the
recent past.
13.2. Water harvesting: The water harvesting structures and the use of harvested
water for life saving irrigation in watershed areas is discussed in detail in lecture No .15
13.3 Crop management
Location specific package of practices for dryland crops have been developed
by dryland research centres and state agricultural universities for all the crops and
cropping systems which include.
a) Selection of crops and cropping systems to suit length of growing season
b) Optimum sowing time
c) Fertilizer schedules and balanced use of plant nutrients for crops and
cropping systems
d) Weed management and package of practices for aberrant weather
e) Contingent cropping
13.4 Alternate land use systems: Alternate land use systems are discussed
separately in lecture No.16
13.5 Land use classification (land capability classification)
Land capability classification is grouping of soils into different classes
according to their capability for intensive use and treatments required for sustained
use. It emphasizes the need for using the land only for what it is suited best to realize
optimum returns, without land degradation. Land capability classification system
developed by USDA is useful for Agriculture. Eight land capability classes are
recognized and designated by Roman numericals from I to VIII. The Roman
numericals indicates increasing limitations and fewer choices for practical field crop
use.
Land capability classes from I to IV are suitable for arable crop production
Land capability classes from V to VIII are suitable for alternate land use systems
CLASS I: This group of soils has few limitations on their use. They are deep (> 90cm),
well drained and nearly levelled. They are fertile or responsive to fertilizer
application. There is no limitation on the type of crops grown. A variety of crops can
be grown intensively with recommended management practices. They are suitable
for intensive cultivation. This group of soils is represented by light green colour in
land use maps
CLASS II: Soils have moderate limitations such as gentle slope, moderate erosion
problem, inadequate depth (22.5–45cm), slight salinity and alkalinity and relatively
restricted drainage. Less intensive cropping systems must be followed. Simple
management practices such as contour cultivation will maintain the soil for crop
production. They are represented by yellow colour in land use maps.
CLASS III: Soils have moderate to severe limitations. The soil erosion, shallow water
permeability, low moisture retentively, moderate salinity and low fertility are the
limitations for their use. Soils can be used for crop production with special
conservation practices like terracing. Smothering crops such as legumes are more
ideal than row crops. They are represented by red colour in land capability maps.
CLASS IV: These soils will have very severe limitations that reduce the choice of
crops. Steep slope, severe erosion, shallow soil depth, salinity or alkalinity restricts
their use for profitable crop production. These lands should be used for close
growing crops or grasses with special soil conservation practices.
CLASS V: These soils generally not suitable for grain crops due to limitations such as
rocky soil, faded areas with no drainage facilities. Pastures can be improved on this
class of land.
CLASS VI: These soils are suitable for growing grasses and forest trees. Limitations
are same as those for class V but they are more rigid. Their use may be restricted to
woodland or wild life.
CLASS VII: These have severe limitations even for growing grass and forest trees.
They are steep soils of extremely shallow depth, used for woodlands and wild life.
CLASS VIII: Not suitable for forest trees and grasslands as they are steep, rough
stony mountains. Land use is restricted to recreation, wild life etc.,
Capability classes can be sub divided into sub classes with in each class based
on special limitations. They are designated by adding small letter c, e, s or w to roman
numerical.
c : shows that chief limitation is climate, low rainfall, too cold or too dry
(very high or very low temperature)
e : chief limitation is soil erosion
s : main limitation is soil character like depth (shallow depth, stony, salinity,
rocky)
w : soil wetness, excess water in or on soil interferes the plant growth