Page 94 - Enzymes in Tropical Soils

82 Enzymes In Tropical Soils

5.5 Regulating the Contents of Soil Organic Matters,
Organic C, and Total N

The linear relationship between activities of soil enzymes and soil organic
matters, organic C, or total N suggests that the activities of soil enzymes may be
regulated by manipulating the contents of soil organic matters, organic C, or total
N. The ratio of C/N is another variable of concern, because it will determine the
population and activities of soil microorganisms producing soil enzymes. In
general, the production of soil enzymes may be accelerated at low C/N ratios by
increasing both organic C and total N. With high contents of C and N, the soil
microorganisms may have enough N to increase their populations and enough C for
their energy in conducting their activities. Low organic C might be enhanced by
addition of organic matters and low N by adding N-sources such as Urea-N.
Data reported by Yusnaini et al. (2007) supports this suggestion.
Substituting chemical fertilizers with organic fertilizers (green or chicken manures)
was shown to increase the activities of phosphatase and -glucosidase (Table 5.13).
Tejada et al. (2010) also reported that cattle dung increased the soil organic matter
content, and hence, also the activities of soil microorganisms, dehydrogenase,
urease, -glucosidase, phosphatase, and arylsulfatase caused by more labile
fractions of organic matters in cattle dung. ‘Night soil’ was also demonstrated to
increase the soil total N and growth of corn (Table 5.14) (Banuwa et al., 2003a;
2003b; Banuwa and Damai, 2003).

Table 5.14. Effects of night soil on soil N, P, K and growth of corn*.

-1
Night Soil (Mg ha )
No. Variables Unit
0 15 30 45 60
-1
1 Total N g kg 1.4 1.8 1.7 2.2 1.8
-1
2 Available P mg kg 0 3.1 3.3 3.4 3.5
-1
3 Exch. K mg kg 7.5 8.1 8.3 9.0 11
4 Plant Height cm 13.1 13.6 13.7 14.0 14.6
Shoot Dry-
5 g 6.7 7.1 8.7 9.5 9.8
Weight

*Adapted from Banuwa et al. (2003a)

Abdul Kadir Salam - 2014