Page 33 - Ilmu Tanah

20 The Chemistry and Fertility of Soils under Tropical Weeds

Chapter 2

The Soil – Weed Interrelationships

2.1 The Soil – Water – Nutrient – Weed Relationships
2.2 The Release of Nutrient Elements from Soil Minerals and Organic
Matters
2.3 The Effects of Weeds on Nutrient Element Release from Soil Minerals
and Organic Matters
Key Questions

J -
ust like plants, crops, and all vegetation, weeds directly and indirectly interact
with the soil system. All absorb nutrient elements from soil water and excrete
+
H ions in exchange of cation absorption or OH ions in exchange of anion
absorption. In addition, all also excrete organic acids into the soil solution where
they absorb nutrient elements from, which in turn acidify the soil ambience. The
+
net excretion of H ion, and also the evolution of CO 2 produced by weed roots and
its associated microbial respiration, may cause the soil acidification even more
intensively and significantly affect other properties of soil environment. As pointed
out previously, weeds are significantly different from other vegetation; they are
+
progressive, expansive, and competitive. Therefore, weeds may produce more H ,
organic acids, and CO 2 , particularly those that have high root-to-shoot ratios
(Salam, 2019).
These characteristics of weeds may enable weeds to stimulate changes in
several soil chemical properties since weed roots are related to other soil
components like soil mineral matters and soil organic matters. As discussed

Abdul Kadir Salam and Nanik Sriyani – 2019