MODULE 1 Flashcards
Irrigation – application of water into the soil; in some areas,
irrigation means to supplement rainfall and serves to
increase production
Irrigation –
– removal of excess water within or on the soil; it can be
natural or artificial
Drainage
Advantages of Irrigation and Drainage:
-increase cropping efficiency
-increase crop productivity and yield
-increase cropping intensity
Agriculture consumes ——-of our total water consumption, and the
majority of this consumption is accounted for by irrigation.
Moreover, roughly half of all harvested rice area and ——-of the
total rice output are irrigated rice.
82% , 70%
the largest irrigation scheme,
servicing about 44 % of the total irrigated land
National Irrigation System (NIS) -
- relative proportion
of variously sized
groups of mineral
particles in a
particular soil or
horizon
Soil Texture
– represents the soil which is made up of air, water and
solids.
Soil System
TOTAL VOLUME
VT = Va + Vw + Vs
Vv = Va + Vw
determines the amount of pore spaces within the soil
- amount of water a soil can hold in a saturated condition
c. Porosity (n)
- the ratio of the volume of
voids in a soil to volume of
solids
Void Ratio (e)
e = Vv / Vs = n / 1-n
Degree of Saturation (DOS)
DOS =( Vw-Vv) x 100
lateral movement of water in the ground surface
surface runoff -
lateral movement of water below water table
seepage -
flow of water from the ground surface into the soil
infiltration -
further downward movement of water into the soil
percolation -
3 types of Moisture Content Measurement
Direct Method
b. Feel and Appearance
c. Bouyoucos Method
d. Tensiometers
- uses the electrical properties of the soil to determine its
moisture content
. Bouyoucos Method
Soil water content and matric potential are not uniquely
related and depend on the path of saturation or desaturation
- Difference in mc readings even same tensiometer readings
Hysteresis
- amount of water the soil profile will hold when all its pore
spaces are filled up
Saturation Point
- soil is allowed to drain 2-3 days
- amount of water the soil profile will hold against the soil
moisture tension of 1/3 bar
Field Capacity
- amount of water the soil profile will hold against the soil
moisture tension of 15 bar
Permanent Wilting Point
- amount of water the soil profile will hold against the soil
moisture tension of 10,000 bar
Hygroscopic Point
causes the dissimilar particles and/or surfaces to
cling to one another
Adhesive force -
similar or identical particles/ surfaces
to cling to one another
Cohesive force -
due to the effect of gravity
Gravitational force -
caused by salt or ion concentration differences or
gradients
Osmotic forces -
water on the soil grains that is not capable
of significant movement by the action of gravity or capillary
forces
Hygroscopic water -
*water that exists in the pore spaces of the soil
and is retained against the force of gravity in a soil that permits
unobstructed drainage
Capillary water -
water that will readily move out of the soil
if favorable drainage is provided
- Gravitational water -
*held too tightly by capillary forces and is
generally not accessible to plant roots
Unavailable water -
difference between gravitational and
unavailable water
- Available water -
drains quickly from the root zone under
normal drainage conditions
- Gravitational water -
drains quickly from the root zone under
normal drainage conditions
- Gravitational water -
