eChapters

1.1. Definition

Soil: Thin layer of earth’s crust made up of disintegrated and decomposed rocks, complex mineral compound, organic matter, water/air and living organism like bacteria, fungi, insects and worms and serves as the natural medium of growth of plants.

Provides nutrients, moisture, anchorage (support) and air to plants.

Parent materials are igneous rocks, sedimentary rocks and metamorphic rocks.

Soil Science: Science dealing with soil (Natural resource) on the surface of the earth, including pedology (Soil genesis, classification and mapping), physical, chemical, biological and fertility properties and their relation to management for crop production.

2.1. Soil structure

Important physical properties of soils

Soil texture

Soil structure

Surface area

Soil density

3.1. Soil colloids

Clay fraction of the soil contains particles less than 0.002 mm in size.

Particles less than 0.001 mm size possess colloidal properties and are known as soil colloids.

4.1. Role of soil microorganisms

Soil N utilization by plants.

Dead organic matters decomposed.

Nutrient transformation.

Physical and chemical properties of soil.

CO₂ content.

Soil formation.

5.1. Organic matter

In sandy soil, the sticky and slimy organic materials cement the sand particles together to form aggregates.

In clayey soil, it modifies the properties of clay by reducing its cohesiveness and making clay more crumby.

6.1. Humus

Fraction of organic matter.

Complex and resistant mixture of brown or dark brown amorphous and colloidal organic substance.

6.2. Humus formation

1. Decomposition: Chemicals in the plant residues are broken down by soil microbes.

Simpler chemicals are metabolized into new compounds in the body tissue of soil microbes.

New compounds are subjected to further modification and synthesis as the microbial tissue is subsequently attacked by other soil microbes.

Involved in plant metabolic functions and the plant cannot complete its life cycle without the element.

7.1. Plant nutrient concentration and plant growth

1. Deficient

Lowest concentration of an essential element that limit yield severely and cause distinct deficiency symptoms.

8.1. Classification of essential nutrients

8.1.1. Based on the amount required by the plant

Major nutrients-Required in large quantities eg. N, P, K.

Secondary nutrients-Required in lesser quantities compared to major nutrients eg. Ca, Mg, S.

Micronutrients-Required in trace quantities eg. Fe, Mn, Zn, Cu, B, Mo.

9.1. Nutrient deficiency of corrective measures

9.1.1. Major and secondary nutrients

Any material of natural or synthetic origin added to the soil to supply one or more plant nutrients.

10.1. Classification of fertilizers

10.1.1. Straight fertilizers

Supply only one primary plant nutrient, namely nitrogen or phosphorus or potassium.

Eg. Urea, ammonium sulphate, potassium chloride and potassium sulphate.

Word manure derived from French ‘Manoeuvrer, means to manipulate, to work, to produce crop.

11.1. Sources of organic wastes

Cattle shed wastes, dung, urine and slurry from biogas plants.

Human habitation wastes-night soil, human urine, town refuse, sewage, sludge and sullage.

Poultry jitter, droppings of sheep and goat.

Slaughterhouse wastes-bone meal, meat meal, blood meal, horn and hoof meal, fish wastes.

Byproducts of agro industries-oil cakes, bagasse and press mud, fruit and vegetable processing wastes etc.

12.1. Problem soils

Chemical constraints: Salinity, sodicity, acidity and nutrient toxicities

Physical constraints : High or low permeability, sub soil hard pan, surface crusting, fluffy paddy soils, sandy soils etc.

13.1. Soil survey and soil mapping

Refers to study and mapping of soils in the fields.

Process of classifying soil types and other soil properties in a given area and geo-encoding such information.

Draws information on geomorphology, theories of soil formation, physical geography, analysis of vegetation and land use patterns.

Primary data for the soil survey are acquired by field sampling and by remote sensing.

Remote sensing principally uses aerial photography (Illuminating the object/ target with pulsed laser light and measuring the reflected pulses with sensor), but LiDAR ( Light Detection and Ranging) and other digital techniques.

14.1. Soil fertility

Ability of the soil to supply essential plant nutrients during growth period of the plants

Crop producing capacity of the soil

1.1. Dry farming (Dryland farming)

Cultivation of crops in a region where the annual rainfall is more than 750 mm.

Semi arid crops with growing period of 75-120 days.

Crop failure is less frequent.

Moisture conservation practices are necessary.

Major 2 types of erosion (i) soil erosion and (ii) wind erosion

2.1. Soil erosion

Detachment of soil particles from the surface • Transportation by water, wind, ice or gravity.

3.1. Conventional farming

Refers to the use of synthetic chemical fertilizers, pesticides, herbicides and other continual inputs, genetically modified organisms, heavy irrigation, intensive tillage and concentrated monoculture production.

Highly resource and energy intensive, but also highly productive.

Conventional farming typically involves monocropping, but very expensive.

1.1. Watershed development

Refers to the conservation, regeneration and judicious utilization of all the resources viz., land, water, vegetation, animal and human within a particular watershed in integrated manner.

Water drainage area on earth’s surface from which runoff, due to precipitation, flows into a single to a larger stream, a river, a lake or the ocean.

1.2. Concept of watershed management

Planning and design of soil and water conservation structures such as bunds, waterways, overflow structures, water harvesting structure.

2.1. Definition

Land which is presently lying unused or which is not being used to its optimum potential due to some constraints

3.1. Land use classification

3.1.1. Classes

Capability class is the broadest category in the land capability classification system.

Class codes 1, 2, 3, 4, 5, 6, 7, and 8 are used to represent both irrigated and non-irrigated land capability classes.

Class 1: Soils have slight limitations that restrict their use.

Class 2: Soils have moderate limitations that reduce the choice of plants or require moderate conservation practices.

Class 3: Soils have severe limitations that reduce the choice of plants or require special conservation practices or both.

4.1. Highlights of the report on number and area of operational holdings (2015-16)

Total number of operational holdings in the country has increased from 138 million ha in 2010-11 to 146 million ha 2015-16 i.e. an increase of 5.33%.

Number of operational holders in different states

Uttar Pradesh (23.82 million ha)

Bihar (16.41 million ha)

Maharashtra (14.71 million ha)

Madhya Pradesh (10.00 million ha)

Karnataka (8.68 million ha)

5.1. Types of farming

Arable: Crops.

Pastoral: Animals.

Mixed: Crops and animals.

Subsistence: Grown just for the farmer and his family

Commercial: Grown to sell.

Intensive: High inputs of labour or capital usually small.

Extensive: Low inputs of labour or capital.

Sedentary: Permanently in one place.

Nomadic: The farmers move around to find new areas to farm.

1.1. Status of irrigation in Tamil Nadu

Geographical area of 13 million hectares is ranked eleventh in size among the Indian states.

Net area sown is about 6 million hectares.

3 million hectares or 50% get irrigation facilities.

To achieve maximum possible irrigation efficiencies, there are two approaches.

Modernization of conveyance system down below the reservoirs upto government controlled outlet. Involves mainly the construction and maintenance of head sluices, main canals, branch canals, and distributaries (Modernization of supplier’s side or system level development works)

Modernization below the government controlled outlets upto the drains (Modernization of user’s side or farm level development works). Also known as On-Farm Development Works (OFD).

3.1. Ground water development

3.1.1. Rain water harvesting

Collecting and using precipitation water from a catchments surface.

Extensive rain water harvesting apparatus existed 4000 years ago in the Palestine and Greece.

In ancient Rome, residences were built with individual cisterns and paved courtyards to capture rain water to augment water from city’s aqueducts.

As early as the third millennium BC, farming communities in Baluchistan and Kutch impounded rain water and used it for irrigation dams.

4.1. Water Use Efficiency (WUE)

An efficient irrigation system implies effective transfer of water from the source to the field with minimum possible loss.

To identify the nature of water loss and to decide the type of improvements in the system.

Evaluation of performance in terms of efficiency is prerequisite for proper use of irrigation water.

Term moisture stress is generally applied to the stomata opening and transpiration increases with time until they close due to high temperature.

5.1. Causes of moisture stress in plants

Main reason is extent of transpiration which is affected by leaf size and composition, size and distribution of stomata on leaf, atmospheric humidity, temperature, wind velocity and day length.

High atmospheric temperature due to intense sun and increased transpiration causes closure of stomata and wilting of leaves even, if soil moisture content is not limiting.

This deficit is made up during night due to decreased transpiration.

In plants, moisture content decreases either due to increased transpiration or reduction in absorption or both.

6.1. Quality of irrigation water

Asia per capita water availability has fallen by around 80 per cent during last five decades.

Suitability of waters for a specific purpose depends on the types and amounts of dissolved salts.

Some of the dissolved ions such as NO₃ are useful for crops.

1.1. Cropping pattern

Yearly sequence and spatial arrangement of crops or crops and fallow on a given area.

1.2. Cropping seasons in India

1.2.1. Kharif season: Southwest monsoon

Crops - Rice, cotton, jute, jowar (sorghum), bajra (pearl millet) and redgram (Pigeon pea).

Word manure derived from French word ‘Manoeuvrer, means to manipulate, to work, to produce crop.

2.1. Sources of organic wastes

Cattle shed wastes-dung, urine and slurry from biogas plants.

Human habitation wastes-night soil, human urine, town refuse, sewage, sludge and sullage.

Poultry litter, droppings of sheep and goat.

Slaughter house wastes-bone meal, meat meal, blood meal, horn and hoof meal, fish wastes.

Byproducts of agroindustries-oil cakes, bagasse and press mud, fruit and vegetable processing wastes.

3.1. Integrated nutrient management

Maintenance of soil fertility and plant nutrient supply at an optimum level for sustaining the desired productivity through optimization of all possible sources of organic, inorganic and biological components in an integrated manner.

3.2. Concepts

Regulated nutrient supply for optimum crop growth and higher productivity.

Improvement and maintenance of soil fertility.

Zero adverse impact on agro – ecosystem quality by balanced fertilization of organic manures, inorganic fertilizers and bioinoculants in an integrated manner.

4.1. Physiological disorders in field crops

Identification of physiological disorders in agricultural crops

5.1. Irrigation requirement of field crops

1.1. FYM compost

Decomposed mixture of dung and urine of farm animals along with litter and left over materials from roughages or fodder fed to the cattle.

Farmyard manure contains 0.5% N, 0.2% P₂O₅ and 0.5% K₂O.

Urine contains one per cent nitrogen and 1.35% potassium.

10 to 20 t/ha is applied, but more than 20 t/ha is applied to fodder grasses and vegetables like potato, tomato, sweet potato, carrot, radish, onion etc., respond well to the farmyard manure.

Crops like sugarcane, rice, oranges, banana, mango and coconut respond good to FYM.

Vermicomposting is the process of turning organic debris into worm castings by earthworms.

Earthworms feed on decaying material, pass through alimentary canals and excreted as castings.

pH of the castings is 7 (neutral) and the castings are odourless.

Contain high amounts of nitrogen, potassium, phosphorus, calcium, and magnesium.

Contains 5 times the available nitrogen, 7 times the available potash, and 1 ½ times more calcium and rich in humus.

Improves aeration, porosity, structure, drainage, and moisture holding capacity.