In my channel Asha Latha Kothapalli @biologyintelugu I am adding a new video on acid soils and alkaline soils and methods to control their pH.
pH is the concentration of hydrogen ions in a volume of solution. ph is a number. Total number of hydronium ions and hydroxyl ions in a given solution is always 14. If pH is 7 that solution is neutral. If pH is greater than 7 it is base,pH is less than seven it is acid.
Soil contains cations like Na+, K+, Ca+2, Mg+2,Al +3
Anions like Cl+1, NO3-1, CO3-2, SO4-2,PO4-3
How to measure the pH of the soil:
Water or Calcium chloride is added to soil stir well occasionally for two hours. We can test the filtered water with Litmus paper or indicator solution or electronic pH meter or by spectrophotometer.
Why should we measure the pH of the soil:
Before preparing the soil for planting we should measure pH. So that we know that the soil is neutral or acidic or alkaline. Which crop should be grown in that soil and proper crop management can be done.
Factors affecting soil:
Minerals composition in the parent rock from which soil is formed.
Leaching of cations. If leaching is more the soil is acidic or leaching is less the soil is alkaline.
pH suitable for agriculture land is 5.5 -7.5
Soil profile:
Soil has different horizons. O,A,E,B,C&R. Through the E horizon water leaches down. Clay particles,Fe,Al, and organic compounds will be more in the B horizon. CaCO3 and weathering rock are in the C horizon. Horizon A is the one with humus and minerals suitable for plant growth.
Reasons for acidity of the soil:
Natural causes: Carbon dioxide in the air or soil dissolves in rainwater forms Carbonic acid. This Carbonic acid dissolves in water and gives bicarbonates. These bicarbonates leach into soil along with cations except Aluminium. Hydrogen ions will be more, pH is less means acidity more.
Organic compounds in the soil decompose more and pH of the soil is less.
While plants are growing plants take more cations. To maintain equilibrium of ions plants release Hydrogen ions or release organic acids to get Iron from the soil. This lessens the pH.
Human activities:
By burning fossil fuels gasses like Carbon dioxide,and Sulphur dioxide enters into the atmosphere. These gasses dissolve in water and form acids. This causes acid rains results in lessening pH
Using more Ammonium salts lessens the pH of soli. Due to nitrification Ammonium changes into nitrites and releases Hydrogen ions.
Mining near cultivation leads to acidic soil.
Reasons for Alkali soil:
Natural causes:
Parent rock which weathering contributes more alkaline metal, Sodium. Alkaline soils are rich in Sodium Carbonate and Sodium bicarbonate.
Excess rainfall and temperature leads to alkaline soils
Leaching of ions is not proper in clay soil, which leads to alkaline soil.
Underground water which is at low heights springs out due to capillary activity of the soil leads to alkaline soil.
Human activities :
When coal rich with calcium carbonate is burned in thermal power houses Calcium oxide enters into air. When it dissolves in water it changes into Calcium hydroxide. It reacts with Sodium bicarbonate and forms Calcium carbonate. It precipitates in water. Sodium bicarbonate changes into Sodium carbonate. It raises the alkalinity of soil.
In preparation of Sodium salts like Sodium bicarbonate, Sodium carbonate and Sodium chloride , some of these salts dissolve in water resources and raise the pH of water.
Effects of acidity on plants :
Excess of Hydrogen ions changes the permeability of cell membrane.
Toxicity of Aluminium and Manganese increases.
Aluminum shows an effect on root formation and root development that results in deficiency of nutrients.
Excess Manganese results in crumple of leaves.
Alkaline soil is not favorable for nitrogen fixation bacteria.
Effects of salinity on plants:
Clay soils are alkaline soils. Water will not leach out. So the water becomes muddy. When water evaporates soil becomes hard. The salts remain on the soil layer. The pH of the soil is more than 8.5.
Sodium carbonate said bicarbonates make the soil swell and the structure of the soil changes. Seed will not germinate. Number of the plants that survive in this soil is very less. This soil is not suitable for plant growth.
How to increase the pH of acidic soils:
Raising pH means neutralising acidic soil.
Lime should be added to soil to neutralise. Calcium compounds like Calcium carbonate,Calcium oxide,Calcium hydroxide and calcium magnesium carbonate.
Adding biochar.
How to reduce pH of soil:
Use compost manure or Ammonium salts,or gypsum or urea or superphosphate.
Water management should be perfect. Separate drainage canal should be there.
Salts should be separated with spades . Irrigation land should be made into small plots and water should be filled for a week then drain the water by a separate canal.
19 сен 2024
