Page 171 - Ilmu Tanah Book

158 The Chemistry and Fertility of Soils under Tropical Weeds

10.2 The Availabilities of Plant Nutrients under Weed

Management

The availabilities of macro and micronutrients in soils under weeds may
increase significantly. The increase is caused by several mechanisms. The most
important sources of nutrients in soil minerals and organic matters may speed up
the release of nutrient elements through soil mineral weathering and organic
matter decomposition by the decrease in soil pH and the increase in soil enzymatic
activities. The supplies of nutrient elements may stay high as long as the soil pH
relatively low and the soil enzymatic activities relatively high. The presence of
organic acids which may act as organic complexing agents may maintain the
availability of these elements
The increase in soil C and organic matter maintains sufficient soil moisture
content which may make the dissolved nutrient elements to be available to plants.
In addition, the increase in soil CEC may maintain nutrient reserves available to
plants. Higher CEC also makes the mineral weathering continues and maintain the
availability of nutrient elements from soil mineral sources. The increase in soil
moisture content also maintain higher microbial and earthworm population and
activities, and production of enzymes. Higher organic matter decomposition also
releases nutrient elements from organic sources. Earthworms also produce faces
that contain nutrient elements.

10.3 The Use of Effective Weeds

It is obvious that weed roots may increase the fertility of soils by improving the
soil chemical, physical, and biological properties. Therefore, it is probable that
weeds are used in the management of soils for crop plants. However, it is
important to first select effective weeds to conduct this mission. A little number of
weeds are reported to employ in this mission even though further researches must
be conducted. Research must not only focus on the effectiveness of weeds in
enhancing the soil fertility but also on how the effective weeds are applied in crop
production. Such alternatives as to employ weeds in the same time during plant
growth or to employ weeds before planting the main crops are one of the choices.
The most important is how to get the benefit of increased soil fertility by the
presence of weeds.

Abdul Kadir Salam and Nanik Sriyani – 2019