Significant of soil temperature in crop production

• Direct effect in seed germination and root system
• Effect in terms of respiration
• Nitrification
• Oxidation of organic matters
• Micro-biological process
• Indirect effect in growth of plants and its yield

a) Effect on microbial activity:

• Soil temperature influences the microbial growth and activity as well as decomposition of soil organic matter which is restricted below 10 °C.
• So, Composting is faster during summer than in winter season.
• The rate of microbial activity such as respiration becomes double for every 10 °C rise in soil temperature but at low temperature it drops (due to this reason farmers stores potato and ginger in the soil).
• The activity of ammonifying and nitrifying bacteria, celluytic bacteria, Actinomycetes etc decreases as the soil temperature decreases below 15 °C. Better microbial activity is obtained at constant temperature than fluctuating temperature.
• Nitrogen fixation is favorable in temperature range of 5 to 27 °C. However, higher temperature leads denitrification process and volatilization. Soil bacterial become inactive below 5 °C and death of bacteria occurs above 30 °C.

b) Effect on seed germination:

• The minimum temperature for the germination of the winter crops such as rye, mustard, pea etc is 1 to 3 °C and other winter crops like sugar beet is 5-8°C. Most of the winter crop will not germinate if the soil temperature is more than 35 °C. Soil temperature must be in the range of 14 to 20 °C for wheat and Pea. Potato and sunflower require more than 5 °C for germination and bean, corn etc. require above 10 °C for germination.
• Seed may not germinate due to higher or lower temperature even if they are physiologically mature (Quiescence).
• Seedling emergence is optimum at 26 to 34 °C.

c) Effect on root growth:

• Minimum and maximum soil temperature for the root growth is specific to the crop species.
• The development of the root above maximum and below minimum temperature is restricted.
• The initiation of adventitious roots of cereal crops is also influenced by soil temperature whose range is in between 10-30 °C.

d) Effect on crop growth:

• The minimum temperature required for growth and full maturity of crop is 12-17 °C for cotton, 5 to 6 °C for oat and potato etc.
• Similarly, rice, maize etc. can tolerate up to 35 °C for good production; Sugarcane can tolerate up to 38 °C.
• For potato, above 24 °C, there will be excessive branching of young sprouts and plant may seem in better appearance but there will be drastically decrease in tuber yield above 29 °C.

e) Effect on nutrient availability:

• The rate of absorption of water and nutrient uptake is low in cool soil and it increases with increase in soil temperature.

f) Removal on soil contaminants:

• The removal of certain organic pollutants from contaminated soils can be accomplished by raising the soil temperature.

g) Effect of freezing and thawing

• When soil temperature fluctuates above and below 0 °C, water in soil undergoes cycles of freezing and thawing.
• Alternate freezing and thawing leads to the formation of ice crystals in the soil and causes structural deterioration of the soil.