Page 95 - Enzymes in Tropical Soils

Enzymes in Tropical Soils 83

One of the reason for the differences in soil organic matter contents is the
types of vegetation grown on the soils. As previously shown, some research
reports (Chan, 1997; Studdert et al., 1997) showed that the organic matter
contents in soils planted with grasses were higher than those planted with food
plants. Therefore, grasses may be used to regulate the soil organic matter contents
of degraded soils. Grasses may also be used to increase the soil organic matter
contents by rotation of food plants with grasses. The more frequent the grasses
are used between food plants, the more effective the role of grasses in enhancing
the soil organic matter contents (Studdert dkk., 1997). Salam et al. (2001) also
reported that the organic and total N in a coffee plantation with P. conjugatum
were higher than those with natural vegetation or control.
Another important method to preserve and enhance the soil organic C, total
N, and organic mater content is employing a suitable tillage system (Salinas-Garcia
et al., 1997; Watts et al., 2010). It has been previously pointed out that
conservation tillage increased the soil organic matter contents including the total C,
fulvic acid, and humic acid (Klein and Koths, 1980; Sarno et al., 1998; Salam et al.,
1998c). Sarno et al. (1998) showed that the total C, humic acid, and fulvic acid
were higher in the no-tillage and minimum tillage soils that that in the conventional
tillage soil. Similarly, Salam et al. (1998c) found that the activities of acid and
alkaline phosphatases as well as -glucosidase were higher in the no tillage and
minimum tillage soils than that in the conventional tillage soil. This means that no-
tilage and minimum tillage systems are better than conventional tillage.
Conventional tillage may drastically degrades the soil organic C levels.

Important Questions

1. What is the difference between organic matter and humus in soils? Compare the
contents of organic matter in peat, muck, and mineral soils!
2. What factors affect the soil organic matter contents? Explain!
3. The organic matter content decreases with the soil depth. Explain why!
4. Compare the organic matter contents in soil planted with grasses and food plants!
5. What is humic substance? What are the differences between Humic and Non-Humic
Substances?
6. Explain the differences between Humin, Humic Acids, and Fulvic Acids! How can
these substances be fractionated?
7. Explain the benefits of Humic Substances in soils!

Abdul Kadir Salam - 2014