171-176 Flashcards
What is flocculation in soil science?
The process where colloidal particles are coagulated by adding oppositely charged ions.
What is the order of effectiveness of different ions in flocculation?
$Al^{+3}>Ca^{+2}>H^{+}>Mg^{+2}$
What is the sequence of availability/absorption of nutrients in soil?
Nitrogen > Potassium > Phosphorus
Which nutrients are readily available in soil with a pH less than 6.0?
Aluminum (Al)
Which nutrients are readily available in soil with a pH between 6.0-6.5?
Phosphorus (P)
Which nutrients are readily available in soil with a pH greater than 7.0?
Calcium (Ca)
How does soil pH affect the availability of Calcium (Ca) and Molybdenum (Mo)?
The availability of Ca and Mo increases with an increase in soil pH.
What is active acidity in soil?
Acidity due to the presence of hydrogen ($H^{+}$) and aluminum ($Al^{+3}$) ions in the soil solution.
What is exchange acidity in soil?
Acidity due to hydrogen ($H^{+}$) and aluminum ($Al^{+3}$) ions adsorbed on soil colloids.
Which ions increase in concentration in acidic soils
and which nutrients decrease?
Which Indian states have the highest acidic soils?
West Bengal
What materials are used to manage acidic soils?
Agricultural liming materials like oxides
What are saline soils and where are they found?
Soils with a high concentration of soluble salts (chlorides and sulfates of sodium and calcium)
How is soil salinity measured?
By measuring the electrical conductivity (EC) of the soil.
How are saline soils reclaimed?
By flooding or leaching soluble salts with good irrigation water
What are alkaline soils and where are they found?
Soils with high pH (greater than 8.5) due to excess sodium carbonate ($NaCO_3$) and sodium bicarbonate ($NaHCO_3$)
What type of fertilizer should be used in alkaline soils instead of urea?
Calcium Ammonium Nitrate (CAN) or Diammonium Phosphate (DAP).
How are alkaline soils reclaimed?
By using gypsum
Name two salt-tolerant field crops.
Barley
Name two salt-tolerant fodder crops.
Rhodes grass
Name two salt-tolerant vegetable crops.
Spinach
Name two salt-tolerant fruit crops.
Date palm
Why is gypsum not recommended for saline soils?
Because it can increase the salt concentration due to the sulfate content.
What are soil amendments?
Substances that improve soil physical and chemical properties
What is hygroscopic water?
Water held tightly by soil colloids
What is capillary water?
Water held in the micro-pores of soil between field capacity and hygroscopic coefficient
What is gravitational water?
Free water that drains out of soil
What is soil erosion?
The process of removal of soil particles from the parent body and their transportation by wind or water.
What are the four stages of water erosion?
Splash/rain drop
Which stage of water erosion is the most serious and why?
Sheet erosion
What are the three stages of wind erosion?
Saltation
What is saltation in wind erosion?
The movement of soil particles through a series of jumps or bounces on the ground.
What is surface creep in wind erosion?
The rolling or sliding of larger soil particles along the ground surface.
What is suspension in wind erosion?
The floating of small-sized soil particles in the air.
What is wave erosion?
Erosion caused by the combined action of wind and water.
What is the permissible limit of soil loss in India?
12 tons/hectare/year.
What is anthropogenic erosion?
Erosion caused by human activities such as excessive grazing and deforestation.
What is deposition of soils?
The accumulation of transported soils at a new location.
What are the different types of soil deposition based on transportation source?
Colluvial (gravity)
What is mineralization in soil?
The conversion of an element from an immobilized form to an available form through microbial decomposition.
What is immobilization in soil?
The conversion of an element from an available form to an immobilized form.
What happens during mineralization and immobilization of nitrogen in soil?
Mineralization occurs when the C:N ratio is below 20:1
What is aminization?
The decomposition of proteins into amines
What is nitrification?
The microbial conversion of ammonia ($NH_3$) into nitrate ($NO_3$).
Which microbes mediate nitrification?
Nitrosomonas and Nitrobacter.
What is the optimal pH and temperature for nitrification?
pH 6.5-7.5 and temperature $30-35^{\circ}C$.
What is the major source of phosphorus in humus?
Phytin.
What is the C:N:P ratio in soil?
100:10:1.
What are manures?
Organic materials that supply plant nutrients in small quantities and provide organic matter in large quantities.
What is vermicompost?
Compost prepared with the help of earthworms.
What is night soil?
Human excreta used as manure.
What is green manure?
Undecomposed plant material used as manure.
What is in-situ green manuring?
Growing green manure crops and decomposing them in the same field.
What is ex-situ green manuring?
Collecting green leaves and twigs from other areas to use as manure.
What are fertilizers?
Inorganic materials that supply one or more essential plant nutrients in large proportions.
What are straight fertilizers?
Fertilizers that supply only one major plant nutrient.
What are complex fertilizers?
Fertilizers that supply two or more primary nutrients.
What are mixed fertilizers?
Fertilizers made by physically mixing two or more fertilizers.
What are complete fertilizers?
Fertilizers having all three primary major nutrients (N
What are low analysis fertilizers?
Fertilizers with less than 25% of the primary nutrient.
What are high analysis fertilizers?
Fertilizers containing more than 25% of the total primary nutrient.
What is fertilizer grade?
Refers to the guaranteed analysis of its plant nutrients.
What is fertilizer ratio?
Refers to the relative percentage of N
What is the order of hygroscopic nature of fertilizers (decreasing)?
Ammonium nitrate> Urea > ammonium sulphate> CAN
What is the acidic residual nature of fertilizer?
Anhydrous ammonia > ammonium chloride > ammonium sulphate> urea > ammonium nitrate (lowest).
What is the order of basic residual nature of fertilizer?
Calcium cyanamide > sodium nitrate > di calcium phosphate > calcium nitrate
What is the equivalent acidity of Anhydrous ammonia?
148 meq./100g.
What is the equivalent acidity of Ammonium chloride?
128 meq./100g.
What is the equivalent acidity of Ammonium sulphate?
110 meq./100g.
What is the equivalent acidity of Urea?
84 meq./100g.
What is the equivalent acidity of DAP?
77 meq./100g.
What is the equivalent acidity of Ammonium nitrate?
60 meq./100g.
