Page 112 - Enzymes in Tropical Soils

100 Enzymes In Tropical Soils

presence of cover plants, just like mulches, particularly with good coverage may
also decrease heat absorption by soils. As previously discussed, soil water may
buffer the changes in soil temperature as heat is absorbed. Moistened soils warm
slower than do dry soils because water posseses high heat capacity. This means
that the soil temperature can be managed at a particular value by setting soil
water contentss, soil colors, and soil covers.
Depending on the purposes, sometimes we may increase the soil
temperature, but sometimes we may also decrease the soil temperature. To
increase the soil temperature, soil cover can be decreased so that the sunlight
energy may directly reach the soil sufcace and increase the soil temperature.
Increasing the soil temperature can also be conducted by applying transparent
mulches that may cause a micro-greenhouse effect that may increase the soil
temperature. The short-wave sunlight is absorbed by soil surface, part of it will be
reemitted as long-wafe light. The long-wave light will be heating the soil covered
by the transparent mulches. Deguchi et al. (2009) reported that compost may also
increase the soil temperature.
Decreasing soil temperature can be done by the use of cover plants or dark
mulches so that sunlight can not directly reach the soil surface (Sauer et al., 1996).
Soil wetting may also decrease the soil temperature because water posseses a
relatively high heat capacity that can resist the temperature raise.
Greenhouse can also be used to control the soil temperature through air
temperature management. When the soil temperature is high, the greenhouse air
conditioner can be operated. Conversely, when the soil temperature is low
disturbing the plant growth, the greenhouse heater can be operated.

Important Questions

1. Explain the role of water in affecting the rates of biochemical reactions in soils!
2. Explain the role of temperature in affecting the rates of biochemical reactions in
soils!
3. What is the relationship between soil water and temperature? Explain!
4. What happens with the soil enzymatic activities when the soil temperature or the
soil water increases above the optimum values? Explain!
5. Explain the daily temperature fluctuation of soils with different water content!
6. Explain the general trend in water content of soils with differing textures: sand, silt,
and clay and differing soil aggregation (structures)!

Abdul Kadir Salam - 2014