Problematic Soil

1.SOIL – PHYSICAL, CHEMICAL & BIOLOGICAL CONSTRAINTS

Soil quality’ is the capacity of a specific kind of soil to function within ecosystem and land-use boundaries, to sustain biological productivity, maintains environment quality and sustains plant, animal and human health

Soil health is defined as being a state of dynamic equilibrium between flora and fauna and their surrounding soil environment in which all the metabolic activities of the former proceed optimally without any hindrance, stress or impedance from the latter plant and animal productivity.

Soil quality index

Soil quality Index (SQI) = f ( SP, P, E,H,ER,BD,FQ,MI)

SP- Soil properties, P = Potential Productivity E- Environmental factors H – Health of animal and Human ER- Erodability, BD – Biological diversity FQ = Food quality safety

Components of soil quality

         Soil quality is a composite of individual capacities of the soil to perform three functions viz., (i) crop and animal productivity (ii) environmental protection and safety (iii) Contribution to human and animal health. Productivity function is well understood scientifically and technologically.

TYPES OF INDICATOR

A.  Physical indicator

1. Aggregate Stability

Aggregate stability is an indicator of organic matter content, biological activity, and nutrient cycling in soil.

· small aggregates (< 0.25 mm)

· large aggregates (> 2-5 mm).

2 Available water capacity is the maximum amount of plant available water a soil can provide. It is an indicator of a soil’s ability to retain water and make it sufficiently available for plant use.

3.Bulk density is an indicator of soil compaction.

·         It is calculated as the dry weight of soil divided by its volume.

·          Bulk density is typically expressed in g/cm3.

4.Infiltration is the downward entry of water into the soil

5. Slaking :Slaking is the breakdown of large, air-dry soil aggregates (>2-5 mm) into smaller sized microaggregates (<0.25 mm) when they are suddenly immersed in water

6. Surface crust indicates poor infiltration, a problematical seedbed, and reduced air exchange between the soil and atmosphere.

7. Structure and Macropores

Sand, silt and clay particles are the primary mineral building blocks of soil. Soil structure is the combination or arrangement of primary soil particles into aggregates

Chemical indicators

1. Soil Electrical Conductivity

• Soil electrical conductivity (EC) is a measure of the amount of salts in soil (salinity of soil). It is an important indicator of soil health.

• It affects crop yields, crop suitability, plant nutrient availability, and activity of soil microorganisms which influence key soil processes including the emission of greenhouse gases such as nitrogen oxides, methane, and carbon dioxide.

•  Excess salts hinder plant growth by affecting the soil-water balance.

2. Soil pH

• Soil pH generally refers to the degree of soil acidity or alkalinity. Chemically, it is defined as the negative logarithm of hydrogen ion concentration in the soil solution

• The pH scale ranges from 0 to 14; a pH of 7 is considered neutral.

• If pH values are >7 the solution is considered basic or alkaline

Biological indicators

1. Earthworms

Earthworms are classified into three groups based on their habitat.

• • Litter-dwellers live in the litter, ingest plant residues, and may be absent in plowed, litter-free soil.

  • Mineral soil-dwellers live in topsoil that is rich in organic matter. They burrow narrow channels and feed on a mixture of soil and plant residues.

  • Deep soil-burrowers (night crawlers) dig long, large burrows into deep soil layers.

  2. Particulate Organic Matter

• Particulate organic matter (POM) fraction comprises all soil organic matter (SOM) particles <2 mm and > 0.053 mm in size

• POM is biologically and chemically active and is part of the labile (easily decomposable) pool of soil organic matter (SOM).

3.Soil respiration

• one measure of biological activity and decomposition.

• The rate of CO2 release is expressed as CO2-C lbs/acre/day (or kg/ha/d).

• During the decomposition of SOM, organic nutrients contained in organic matter (e.g., organic phosphorus, nitrogen, and sulfur) are converted to inorganic forms that are available for plant uptake. This conversion is known as mineralization.

• Soil respiration is also known as carbon mineralization.

2. WASTE LANDS

 NWDB defines wastelands as that land  is presently lying unutilized due to different constraints.

Kinds of wastelands

1.Cultivable / Cultural wastelands :

Culturable wastelands include the lands which have the potential for the development of

Vegetative cover and are not being used due to different constraints of varying degrees.

Categories of cultural wastelands

Gullied land/ravinous land

• Gullied land- the gullies are the result of the localized surface runoff affecting the friable

• Unconsolidated material resulting in the formation of perceptible channels resulting in undulating Terrain having a maximum depth of 3m.

• Ravinous land – this category of land contains system of gullies 77 running more or less

Parallel lo each other in deep alluvium and entering a nearby river flowing much lower than the

Surrounding table lands as are found along the courses of many rivers. The ravines are formed by

Gullies developed along river courses

The Ravinous land are categorized into three categories

1.      Shallow – 3-6 meters deep

2.      Medium – 6-9 meters deep

3.      Deep – more than 9 meters deep

Surface waterlogged and marshy lands

This is the land where water table is at /or near the surface and water stands for most of

The year. Water logging occurs due to the rise of sub-soil water-table and this happens almost all

The over-irrigated areas.

Marsh is the land which permanently or periodically is inundated by water and is

Characterized by vegetation that includes grasses and reeds. Marshes are classified into salt,

Brackish and fresh water categories depending on the salt

Degraded/under utilised notified forest land

 Lands as notified under the forest act and those lands with various types of forest cover in

Which denudation of vegetation cover is less than 20% of canopy cover, are classified as

Degraded land.

Degraded pastures/grazing land

All those grazing lands in non-forest areas, whether or not they are permanent pastures or

Meadows, which have become degraded due to lack of proper soil conservation and drainage

Measures fall under this category.

II. Unculturable wastelands

Uncultural wastelands which cannot be used for vegetation are classified as

a) Brown rocky / stony / shut of rocks – The upper surface of these soils are covered with rocks, Stones, boulders and other geological formations. Such land surface is not capable of supporting any

Living organism.

b) Steep sloppy areas – Very steep slopy lands tend to erosion and landslides

c) Snow covered and / or glacier lands – The lands above snowline are perma

3.SOIL CONSTAINTS

1.HIGHLY PERMEABLE SOIL

High permeable soils, also known as sandy or coarse-textured soils, have high infiltration rates and low water-holding capacities. Here are some characteristics and management strategies:

Characteristics

1. High infiltration rate: Water enters the soil quickly, reducing runoff and potential erosion.

2. Low water-holding capacity: Soil retains less water, making it challenging for plants to access water during dry periods.

3. Good aeration: Highly permeable soils allow for good air exchange, promoting healthy root growth.

Management Strategies

1. Frequent irrigation: Irrigate frequently to maintain optimal soil moisture levels.

2. Mulching: Apply organic mulch to reduce evaporation and retain soil moisture.

3. Adding organic matter: Incorporate organic matter to improve soil structure and increase water-holding capacity

[ Highly permeable soils, also known as sandy or coarse-textured soils, have high infiltration rates and low water-holding capacities. Here are some characteristics and management strategies:

Benefits

1. Reduced erosion: Highly permeable soils reduce the risk of erosion due to runoff.

2. Improved aeration: Good aeration promotes healthy root growth and microbial activity.

3. Warmer soils: Highly permeable soils tend to warm up faster in the spring, allowing for earlier planting.

Challenges

1. Drought stress: Plants may experience drought stress due to the low water-holding capacity.

2. Nutrient leaching: Nutrients may leach through the soil profile, reducing their availability to plants.

3. Soil compaction: Highly permeable soils can be prone to compaction, reducing soil aeration and water infiltration.

2.FLUFFY SOIL

Fluffy soil, also known as loose or light soil, requires special management to maintain its structure and fertility.

Management

1.400 kg  stone roller could be used to compact soil after sowing

2.Add organic matter: Incorporate compost, manure, or other organic materials to improve soil structure and fertility.

3.Mulch: Apply a layer of mulch to retain moisture, suppress weeds, and regulate soil temperature.

4.Avoid over-tilling: Minimize tilling to prevent soil compaction and damage to soil structure.

5.Use cover crops: Plant cover crops to stabilize the soil, reduce erosion, and add organic matter.

Benefits

1.Improved soil structure: Fluffy soil management can improve soil aeration, water infiltration, and root growth.

2.Increased fertility: Adding organic matter and using cover crops can increase soil fertility and promote healthy plant growth.

Soil crusting is a common issue that affects soil health 

Causes

1. Heavy rainfall or irrigation: Intensive rainfall or irrigation can cause soil particles to become dislodged and form a crust.

2. Soil texture: Soils with high silt or clay content are more prone to crusting.

3.Lack of organic matter: Soils with low organic matter content are more susceptible to crusting.

4.Tillage and traffic: Intensive tillage and traffic can damage soil structure, leading to crusting.

Impact

1.Reduced water infiltration: Soil crusting can reduce water infiltration, leading to runoff and erosion.

2. Increased runoff and erosion: Crusted soils can lead to increased runoff and erosion, reducing soil fertility and affecting plant growth.

3. Reduced seedling emergence: Soil crusting can make it difficult for seedlings to emerge, reducing crop yields.

4. Poor aeration: Crusted soils can reduce soil aeration, affecting microbial activity and root growth.

Management

1. Add organic matter: Incorporate organic matter, such as compost or manure, to improve soil structure and reduce crusting.

2. Conservation tillage: Use conservation tillage practices to minimize soil disturbance and preserve soil organic matter.

3. Mulching: Apply mulch to protect the soil surface and reduce crusting.

4. Crop selection: Choose crops that are tolerant of crusted soils or have deep roots to break through the crust.

5. Soil conditioning: Use soil conditioners, such as gypsum or lime, to improve soil structure and reduce crusting.

SURFACE CRUSTING

Surface crusting is a common issue in sodic soils:

Causes of Surface Crusting

1. Sodium dispersion: High sodium levels can cause clay particles to disperse, leading to crust formation.

2. Rainfall impact: Rainfall can cause soil particles to break down and form a crust.

3. Soil texture: Soils with high silt and clay content are more prone to crusting.

Effects of Surface Crusting

1. Reduced water infiltration: Crusting can reduce water infiltration, leading to runoff and erosion.

2. Increased soil erosion: Crusting can increase soil erosion, especially on sloping lands.

3. Impacted seedling emergence: Crusting can impede seedling emergence and crop establishment.

Management Strategies

1. Gypsum application: Applying gypsum can help reduce sodicity and improve soil structure.

2. Organic matter addition: Adding organic matter can improve soil fertility and structure.

3. Conservation tillage: Reducing tillage can help minimize soil disturbance and preserve soil structure.

4. Mulching: Applying mulch can help reduce soil crusting and improve water infiltration.

Benefits of Management

1. Improved water infiltration: Managing crusting can improve water infiltration and reduce runoff.

2. Reduced soil erosion: Managing crusting can reduce soil erosion and preserve soil health.

3. Enhanced crop productivity: Managing crusting can support crop productivity and sustainability.    

SUBSURFACE HARD PAN

Subsurface hardpan is a compacted layer of soil that can impede water and root growth:

Causes of Subsurface Hardpan

1. Compaction: Heavy machinery or foot traffic can cause soil compaction, leading to hardpan formation.

2. Sodicity: High sodium levels can contribute to hardpan formation.

3. Soil texture: Soils with high clay or silt content are more prone to hardpan formation.

Effects of Subsurface Hardpan

1. Reduced water infiltration: Hardpan can reduce water infiltration, leading to waterlogging and runoff.

2. Impeded root growth: Hardpan can impede root growth, reducing crop productivity.

3. Increased soil erosio: Hardpan can increase soil erosion, especially on sloping lands.

Management Strategies

1. Deep tillage: Deep tillage can help break up the hardpan, improving soil structure and water infiltration.

2. Gypsum application: Applying gypsum can help reduce sodicity and improve soil structure.

3. Organic matter addition: Adding organic matter can improve soil fertility and structure.

4. Crop rotation: Implementing crop rotation can help improve soil health and reduce hardpan formation.

Benefits of Management

Improved water infiltration: Managing hardpan can improve water infiltration and reduce runoff.

Enhanced root growth : Managing hardpan can support root growth and crop productivity.

Reduced soil erosion: Managing hardpan can reduce soil erosion and preserve soil health.

ERODED SOILS

Characteristics of Wind-Eroded Soils

1. Loss of topsoil: Wind erosion removes fertile topsoil, reducing soil productivity.

2. Coarser texture: Wind erosion can leave behind coarser particles like sand and gravel.

3. Reduced organic matter: Wind erosion leads to loss of organic matter, affecting soil fertility.

4. Increased soil compaction: Wind erosion can cause soil compaction, reducing water infiltration.

5. Changes in soil structure: Wind erosion alters soil structure, impacting water-holding capacity and aeration.

Impacts on Soil Health

1. Reduced fertility: Wind erosion reduces soil fertility due to loss of topsoil and organic matter.

2. Decreased productivity: Wind erosion affects soil productivity, leading to reduced crop yields.

3. Increased erosion risk: Wind-eroded soils are more susceptible to further erosion.

Management Strategies

1. Conservation tillage: Reducing tillage can help minimize soil disturbance.

2. Cover crops: Planting cover crops can protect soil from wind erosion.

3. Windbreaks: Establishing windbreaks can reduce wind speed and erosion.

4. Soil conservation practices: Implementing soil conservation practices can help restore soil health.

Water-eroded soils

Characteristics of Water-Eroded Soils

1. Loss of topsoil: Water erosion removes fertile topsoil, reducing soil productivity.

2. Gullies and rills: Water erosion can create gullies and rills, altering soil landscape.

3. Increased sedimentation: Water erosion leads to sedimentation in water bodies.

4. Changes in soil texture: Water erosion can change soil texture, affecting water-holding capacity.

5. Reduced organic matter: Water erosion can result in loss of organic matter, affecting soil fertility.

Impacts on Soil Health

1. Reduced fertility: Water erosion reduces soil fertility due to loss of topsoil and organic matter.

2. Decreased productivity: Water erosion affects soil productivity, leading to reduced crop yields.

3. Increased soil degradation: Water erosion contributes to soil degradation, impacting ecosystem services.

Factors Influencing Water Erosion

1. Rainfall intensity: High-intensity rainfall can increase water erosion risk.

2. Soil texture: Soils with high sand or silt content are more susceptible to water erosion.

3. Slope steepness: Steep slopes increase water erosion risk.

4. Vegetation cover: Lack of vegetation cover can increase water erosion risk.

Management Strategies

1. Conservation tillage: Reducing tillage can help minimize soil disturbance.

2. Terracing: Terracing can reduce water erosion on sloping lands.

3. Cover crops: Planting cover crops can protect soil from water erosion.

4. Soil conservation practices: Implementing soil conservation practices can help restore soil health.

8.FLOODED SOIL

 I.Characteristics of Flooded Soil

Physical Changes

·    Pores  saturated with water

·    Less aeration

·    Aggregates weak and broken

Biological Changes

·   Less aerobic microbes are present

Chemical Changes

·   The upper zone, a thin 1-10 mm, absorbs oxygen from the water, turns brown in color, and reacts to nitrogen like an unfolded soil. – oxidised zone

·   Lower zone, which extends down as far as the water, is extremely low in available oxygen, turns dark blue or gray in color, and takes on chemical properties quite different from those of the oxidized layer above – Reduced zone

SANDY SOILS MANAGEMENT

1)      Development practices

·    Develop the swamp so as to discourage leaching.

·    Keep the main drain shallow (so it will not “suck” water from the plots). Dig deep peripheral gutters (to intercept groundwaters percolating down from adjacent hillsides).

2)      Varietal Selection

Select a variety which does well under relatively difficult conditions, ie. A variety which can withstand an irregular water regime, nutrient deficiencies, and soil toxicities.

3)      Management Practice

·   Keep a constant. Slow-moving or non-moving flood spread out fertilization by applying top dressings in many small splits. On the plots.

·   To improve the structure and fertility of the soil, as well as to improve its ability to retain water, incorporate large amounts of organic material before and, if necessary, after the growing season

10 . ACID SOIL AND ACID SULPHATE SOIL

 Acid soil is a base unsaturated soil which has got enough of adsorbed exchangeable H’ ions so as to give soil a pH lower than 7.0.

 Genesis of acid soils

(1)   Leaching due to heavy rainfall

Acid soils are common in all regions where rainfall or precipitation is high enough to leach appreciable amounts of exchangeable bases ( C a^ 2- ) M g^ 2- N a^ - and K”) from the surface soils and relatively insoluble compounds of Al and Fe remains in the soil

(ii) Acidic parent material

Some soils developed from acidic parent materials like granite and gneiss may develop soil acidity.

(iii) Acid forming fertilizers and soluble salts

 ·         The use of acid forming fertilizers like ammonium sulphate  NH2 SO 4 and ammonium nitrate NHINO, increases soil acidity.

·         The Al ions displaced from clay minerals by cations are hydrolysed to monomeric and polymeric hydroxyl aluminium complexes as shown below.

Kinds of Soil Acidity

Soil acidity may be of the following two kinds

(1)   Active acidity

It is defined as the acidity that develops due to hydrogen (H) and aluminium (Al”) ions in the soil solution.

(ii) Exchange acidity

It is defined as the acidity that develops due to adsorbed hydrogen (H) and Aluminium (Al”) ions on the soil colloids. The magnitude of this acidity is very high. It is also called potential/reserve acidity.

(iii) Total acidity

Total acidity =Active acidity+ Exchange acidity..

Distribution of acid soils

Out of 157 m.ha of cultivable land in India, 49 m.ha are acidic, if which 36 m.ha have soil pH less than 5.6 and the rest 13 m.ha have soil pH in the range of 5.6 to 6.5

Problems of soil acidity

(1)   Acid toxicity

The acid toxicity includes toxicities of acidic anions as well as H ions.

(ii) Toxicity of nutrient elements

Iron and Manganese

·    The concentration of these two ions (Fe and Al”) in soil solution depends upon the soil reaction.

·    The pysiological disease of rice is found in submerged soils which is popularly known as browning disease.

Aluminium

·   The toxicity of aluminium tends to decrease with an increase in concentration of other cations such as calcium ,  affects plant growth

·    It affects various plant physiological processes like cell division, formation of DNA and respiratioIt restricts the absorption and translocation of important nutrient elements from the soil to the plants like P. Ca, Fe, Mn etc..

     ·    It canses wilting of plantsand  also inhibits the microbial activity in the soil.

(iii) Nutrient availability

 .  Non specific effects -It causes inhibition of root growth and thereby affects the nutrient availability.

 .  Specific effects

     ·  Exchangeable bases: Due to complementary ion effect, exchangeable bases are released preferentially in a fractional exchange.       Deficiency of bases like Ca” and Mg are found in acid soils

·   Nutrient imbalance

 Acid sulphate soil

·         Acid sulphate are drained coastal wetland soils that have become acid (pH<4) due to oxidation of the pyritic minerals in the soil.

·         Undraimed soils containing pyrites need not be acid and they are called potential acid sulphate soils.

 Types of acid sulphate soils

·         Potential acid sulphate soil

·         hey are neutral in pH (6.5-7.5), contain unoxidised iron sulfides,

·          soft, sticky and saturated with water and are usually gel-like muds

·         Actual acid sulphate soils

·         When PASS are exposed to oxygen, the iron sulfides are oxidised to produce sulfuric acid and the soil becomes strongly acidic (usually below pH 4).

10. Lime Requirement of Acid Soil, Liming Materials and Reclamation of

Acid soil

 Lime Requirement

·         Lime requirement of an acid soil is defined as the amount of liming material that must be added to raise the pH to some prescribed value. This value is usually in the range of pH 6.0 to 7.0, s.

·          Shoemaker et al. (1961) buffer method is used for the determination of lime requirement of an acid soi

 Kinds of Liming Materials

 Various kinds of liming materials are used for the correction of soil acidity. They are as follows

 (1)   Oxides of lime

·   It is normally called burned lime or quick lime. Oxides of lime is more caustic than limestones. Burned lime is produced by heating limestone and dolomite as follows.

·   CaCO Heat Limestone CaO+CO

·   CaMg(CO):+Heat CaO+MgO+200:

(ii) Hydroxides of lime

It can be produced by adding water to burned lime and is called slaked lime.

CaO+H₂O -- Ca (OH) + CO

(Burned lime)

It is more caustic than burned lime (CaO). If it is kept open in the moist air, then combination of calcium hydroxide occurs as follows.

Ca (OH)+CO Mg(OH)CO CaCO+HO MgCO,+H₂O

(iii) Carbonates of lime

 These are by products of certain industries and so the content of calcium and magnesium varies. The two important minerals found are calcite (CaCO3) and dolomite (CaMg(CO))

 (iv) Slags

 These are generally three types of slags that are found important.

a. Blast furnace slag It is a by- product of the manufacture of Pig iron. As a liming material, this behaves as calcium silicate. The neutralizing value of blast furnace slags ranges from about 75-90%.

b. Basic slag It is a by-product of the basic open hearth method of making steel from pig iron, which in turn is produced from high phosophorus iron ores. Impurities in the iron, including silica and phosphorus are fluxed with lime and the basic slags are produced. Its neutralizing value ranges from 60-70%

Electric furnace slag This is produced from the electric furnace reduction of phosphate rock

Percent Effective Calcium Carbonate (ECC) or (Neutralizing Index)

The effective calcium carbonate (ECC) rating of a limestone or liming material the product of the calcium carbonate equivalent (CCE) and the fineness factor.

Percent ECC or N.1=CCE x Fineness factor.

Chemical reactions during the process of amelioration

(1)   Oxides of lime (CaO) – When oxides of lime like CaO is applied to an acid soil, it reacts inmediately as follows.

2…Hydroxides of lime (Ca(OH)2) When hydroxides of lime like Ca(OH); is applied for the reclamation of an acid soil, the following chemical reaction takes place

SALINE SODIC SOILS

Salt affected soils occur most extensively in arid climates, but these soils are also found in coastal sea areas where soils are inundated by ocean or sea water.

Common sources of salts

1. Rocks and minerals

The salts primary originate as a result of hydrolysis, hydration, carbonation and oxidation reduction of the easily weatherable minerals inherited from the parent materials viz., halite, gypsum, sulphides, calcite, dolomite, apatite, amphiboles, olivine, feldspars and primary layer silicates.

2. Arid and semi-arid climate

·  Salt affected soils are mostly formed in arid and semi-arid regions where low rainfall and high evaporation prevails.

·  The low rainfall or precipitation in these regions is not sufficient to leach out the soluble weathered products and hence the salts accumulate in the soil.

3. Ground water

Groundwater contains large amounts of water soluble slats which depends upon the nature and properties of the geological material with which water remains in contact.

4. Ocean or sea water

· Ocean water containing 42 x 10 tonnes of dissolved salts (of which 85.6 % is NaCl) is a significant direct source of salts in the soils of the low-lying coastal areas.

· Near the sea coast, the rain water may contain salts upto 200 mg/L, containing high concentrations of chlorides of Na and Mg, but inland rain water is dominated by sulphates and bicarbonates of Ca and Mg.

5. Irrigation water

The application of irrigation water without proper management (i.e., lack of drainage and leaching facilities) increases the water table and surface salt content in the soil.

6. Atmospheric accession of salts

Atmospheric accession of salts in the soil of inland areas can occur as a result of falling dried droplets of ocean water from the atmosphere (aerosol) along with rain water or as dry salt-dust.

7. Salts blown by wind

In arid regions near the sea, appreciable amount of salts are blown by wind year after year and get deposited on the surface soil.

8. Excessive use of basic fertilizers

Use of basic fertilizers like sodium nitrate, basic slag etc., may develop soil alkalinity.

9. Marine rocks and depositsMarine rocks and evaporites developed with the upliftment of many parts of the continents from. The sea ocean are also important sources of salts in the soil. Eg. Localised concentration of salts along the lower Himalayas and the Shiwaliks,