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The Chemistry and Fertility of Soils under Tropical Weeds 73

Chapter 5

Effects of Tropical Weeds on Soil pH

and Enzymatic Activities

5.1 Effects on Soil pH
5.2 Effects of Alang-Alang
5.3 Effects on Soil Enzymatic Activities
Key Questions

R +
oots of all vegetation are unique in that they release some chemicals into
the adjacent soil environment among which are H ions, organic acids
(Table 5.1), and soil enzymes which are very important to suffice the
nutrient elements needed for their growth from various nutrient sources both of
organic matters and mineral matters. Hydrogen ion is released in exchange of
nutrient element cations absorbed by vegetation roots. Combined with those of
+
organic acids, these H ions may lower the soil pH, which may then intensify the
release of plant nutrient elements adsorbed on or contained in the structure of the
primary and secondary minerals. The evolved CO 2 by the respiration in the
vegetation roots may also intensify the decrease in soil pH and the release of
nutrient elements from mineral sources.

Abdul Kadir Salam and Nanik Sriyani – 2019