Page 99 - Ilmu Tanah

86 The Chemistry and Fertility of Soils under Tropical Weeds

Chapter 6

Effects of Tropical Weeds on Soil

Carbon, Phosphorus, Nitrogen, and

Sulfur

6.1 Nutrient Cycles
6.2 Effects of Land-Use Conversion
6.3 Effects of Weed Management
6.4 Effects of Continuous Cropping
6.5 Effect of C and N on Enzymes
Key Questions

L
ike all vegetation, weeds are one of the several agents important in the
carbon cycle or C-Cycle. Weeds absorb a great amount of atmospheric CO 2
and combine it with H 2 O absorbed from soils to produce hydrocarbon and its
derivates contained in organic matters. Similar to that of C, N, P, and S also
encounter cycles called N-Cycle, P-cycle, and S-Cycle, respectively. Nitrogen, P, and
- 2- 2-
S are absorbed by weed roots from soil solution as NO 3 , HPO 4 , and SO 4 ,
respectively. Combined with hydrocarbon, these nutrient elements may form
proteins. Therefore, the whole mass of weeds contain a great amount of carbon
that whenever released in the soil environment it may increase the soil organic C

Abdul Kadir Salam and Nanik Sriyani – 2019