Agriculture Reference
In-Depth Information
GT sheets
General purpose topographical survey sheets.
Gullied land Land badly eroded by water and formed into a network of trenches
and mounds.
Ravines.
Gully plugging Blocking the gullies with earth, brushwood, or gabion to prevent
rush of water in order to contain progress of erosion.
Gypsum
Mineral consisting of hydrous calcium sulphate, used in soil amendment.
Hardy plants Plants that can withstand adverse conditions of harsh weather,
nutrient deficiency, and moisture stress.
HDPE
High density polyethylene.
Head In pumps and water supply systems, the pressure of water expressed in terms
of equivalent height of a water column. Also known as pressure head.
Headwall
In a stopdam or spillway, the main wall that allows flow of water over it.
Heat wave
Sudden and severe rise in atmospheric temperature causing damage to
plants.
Heavy soil Soil with predominant content of clay in it. Heavier soils have finer
particles, they swell on getting moist, and crack on drying up. They are characterised
by better availability of plant nutrients, but poor drainage and root aeration.
Heptachlor A cyclodiene chlorinated hydrocarbon pesticide (C 10 H 5 C l 7 ). It can
cause liver disease in animals and is suspected to cause cancer in humans.
High density polyethylene A kind of polyethylene used in moulding of large mass
objects, such as pipes and water tanks, compared to the low density polyethylene
which is used in manufacture of thin film objects such as polypots. The HDPE is
often used as recycled material in black colour; it is brittle, and has less strength than
LDPE.
Hoeing Tilling, raking, or loosening the earth around plants to prevent loss of subsoil
moisture and to promote aeration and temperature moderation in the soil.
Horizontal integration Level of interaction, co-ordination and communication
between different units at a given level in the organisational hierarchy.
HSL
Hydrostatic level
Humus
Partially decomposed plant or animal matter forming the organic part of
the soil.
Hydrant A discharge pipe with a valve and a spout from which water may be drawn.
Hydrostatic level A device consisting of two wooden graduated staves with the two
ends of a transparent water-filled rubber tube passing over each, indicating level of
water under free atmospheric pressure. The HSL is a simple yet versatile and reliable
instrument for marking contour lines in field, as well as for surveying cross sections
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