Page 125 - Ilmu Tanah Book

112 The Chemistry and Fertility of Soils under Tropical Weeds

Chapter 7

Effects of Tropical Weeds on Soil

Potassium

7.1 The Release of Potassium from Soil Minerals
7.2 The Release of Potassium from Soil Organic Matters
7.3 The Effects of Soil pH on Soil Potassium Release
7.4 The Effects of Weeds on Soil Potassium Release
Key Questions

A
s previously stated, the weed root excretion may lower the soil pH and
increase the soil enzymatic activities. These chemical changes may bring
about the changes in other soil chemical and fertility properties. Among
the most important change is the increase in dissolved and exchangeable K of soils.
Of course with a prerequisite that the related soils contain adequate organic and
inorganic sources of K easily transformed into readily available form for plants by
chemical weathering and enzymatic decomposition.
+
The accumulation of H ions may cause the soil K-mineral dissolution. In the
+
presence of H and water, orthoclase, which is one of the K sources of silicate
minerals may detach its structural K increasing the dissolved K in the soil solution
and in turn may enhance the soil exchangeable K. Any other sources of K may also
dissolve increasing these available forms of K in the soil environment. Some

Abdul Kadir Salam and Nanik Sriyani – 2019