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Soil Tillage and Tilth

Basics of Soil Tillage and Tilth

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Soil Tillage and Tilth

Tillage: It is the manipulation of the soil with tools and implements for loosening the surface crust and bringing about conditions favourable for germination.

Tilth: It is the physical condition of the soil in relation to plant growth.

• Buck scraper (or) levelling plank – major leveling of field.
• Percentage of soil volume occupied by porespace is called “Porosity”.
• Crumb and granular structure is the good soil structure.
Bulk density – It is the mass per unit volume of dry soil.
• Mechanical manipulation of soil at high moisture content is known as “Puddling”.
Peddamadaka → Heavy plough, used for deep ploughing in black cotton soils.
• Levelling implement → Buck scraper.
• Layout of seed bed → Broad bed furrow former; ridges plough bund former.
• Star weeder → used in groundnut for control of weeds.
• Japanese rotary weeder → used in low land rice.
• Seed dril = gorru, Blade harrow = Guntaka.
• Levelling of puddled soil is done by the implement called “Pallamanu”.
• Humus is the end (or) final product of organic matter decomposition. The right time for
incorporation of green manure is at crop flowering stage.

Depth of sowing depends on seed size.
• It is not possible to build up high oraganic matter in Indian soils because of high
temperature.
· It is not advisable to broasdcast fertilizer when there is dew on leaves.
Green manure crop used for reclamation of saline and alkaline soils is Diancha.
• The method of sowing in which all plants get uniform spacing is drilling, seeding behind
country plough.
• Earth rotates from west to east.
• The response of living organisms to regular change in temperature either day (or) night is
known as “Thermoperiodism”.
• Hydrometers – forms of precipitation.
• Orographic rains – Rains caused by mountains.
Solistice → It is the maximum distance between sun and earth. It occurs twice – once each
in South and North of celestial equation during the annual path of earth around the sun.
June – 21st
Dec – 22nd
Equinox : The astronomical day at which light and night are equal, which occurs when the
sun is directly over head of equator.
March – 21st
Septermber – 22nd
• Emmission of surface other than a perfect black body is always less than one.
· Albedo values are highest in winter and sunrise, sunset

S.No. :Surface % of albedo
1. Fresh snow 75 – 95%
2. Dry Sand duke 35-45 %
3. Clay Soil 20-35%
4. Wet sand 20-30%
5. Deciduous forests 10-20%
6. Human Skin bloude 43-45%
7. Dark soil 5-15%

· Heat capacity in the range of 0.3 – 0.6 cal/cm3
· Specific heat : Minerals – 0.18 – 0.20 cal/gm.
Humus – 0 – 45 cal/gm
· The “Grant Anicut” across the river Cauvery in TN was constructed by “Chola King”.
· Large number of tanks are seen in South India, Inundation canals are common in North
India.
· First irrigation commission – 1901.
· Total geographical area – 328 m ha
Average Rainfall – 1200 mm
· Total Precipitation – 400 m ha
· Major source of irrigation in Andhra Pradesh is Canals.
· Anicut – Embankment across a river.
· Ayacut – Irrigation area under a project.
· A structure less soil allows water to percolate too rapidly (or) two slowly.
· Suitable resorting system of water distribution among farmers is “Warabandi”.
· 2/3 of capillary water is available to growing plants in India.
· Musi Project – Nalgonda, Kaddem – Adilabad, Yerralakawa – East Godavari Rayalabanda
diversion scheme – Mahaboobnagar, Vamsadara – Srikakullum and Gajuladinne – Kurnool.
· Soil texture determines the amount of water a soil can hold.
· A platy structure can impede downward movement of water.
· Particle density – 2.65 g/cc, Bulk density – 1.25 to 1.70 g/cc.
Porasity = [(1-B.D/P.D) X 100]
· When all the pores, large and small are filled, the soil is said to be saturated and it at its
“Maximum retentive capacity”.
· Water in large pores move downwards – Gravitational water (or) free water.
· Water in the small pores move because of capillary force and is called “Capillary water”. It
moves more freely than free water. It can move in any direction, but always in the direction
of “Increasing tension”.
· Thin film around soil particles that cannot be used by plants is called “Hygroscopic water”.
· Capillary movement is by adhesive and cohesive forces.
· Water moves from saturated soil to unsaturated layers.
· In moist soils water movement is more uniform than in dry soils.
· At saturation, capillary movement is most rapid in sandy soils and slowest in clay soils. But
in unsaturated, capillary movement is rapid in clay and slow in sandy soils.
· Adhesion – attraction of soil particle and water.
· Cohesion – between water molecule.
· Soil moisture tension is a measure of the tenacity with which water is retained in the soil
and shows the force per unit area that must be exerted to remove water from the soil. It is
usually expressed in atmosphere.
· Soil moisture tension does not indicate the amount of water. To show the amount of
moisture a given soil holds at various tension.
· “Moisture extraction curves” (Soil moisture characteristic curves) must be develoed.
· PF is defined as the logarithm of height in a column of water. Pf value of saturated soil is
‘O’.
· At Field capacity pF 2.54; P.W.P – 4.2 soil moisture tension – 15 bars.
· Movement of irrigation water from the surface into the soil through the soil is called “Water
intake = Percolation + Infiltration”.
· Infiltration is the downward flow of water from the surface into the soil.
· Percolation is the movement of water through soil profile.
· Percolation rate is governed by the permeability (or) Hydraulic conductivity of the soil.
· Permeability is the quality of soil that enables it to transmit air and water.
· Hydraulic conductivity is the co-efficient ‘K’ (Proportionality factor).
· Darcy’s law = V = Ki
V = Effective flow velocity
i = Hydraulic gradient
‘K’ depends on the properties of fluid as well as the soil.
· Seepage is the lateral movement of water in the soil.
· Leaching is removal of soluble salts by passage of water through soil.
· Field capacity is the amount of water a well drained soil held after free water had drains
against held gravity.
· Available water = F.C – PWP
· 1/3 atmospheric tension is usually taken as field capacity of the soil
· Permanent wilting point is the soil moisture to meet transpiration requirements.
· Ultimate wilting point – At this point the plant will die even after providing water.
· A higher water table limits root growth and a raised water table may kill rooots.
· The usual water extraction pattern 40% moisture from the upper quarter 30% from second
quarter, 20% from III, 10% from IV quarter.
· Effective root zone depth is the soil depth from which the crop extracts most of the water
needed for “evapo transpiration”.
· Safflower – very deep root system, cotton – deep root system
· Soil crusting reduces infiltration.


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