Page 59 - Ilmu Tanah

46 The Chemistry and Fertility of Soils under Tropical Weeds

aspects: the inclusion of ecological principles, the use of weed – plant competition
principles, consideration on both economy and environment, integration of all
available control methods that may include selective herbicides, and control of
weed management by professionals.

Table 3.2. The effects of weeds on some chemical properties of soil from Great
Giant Pinapple plantation Central Lampung.

Total N Avail. P Org. C CEC
Weeds -1 -1 -1 -1
(g kg ) (mg kg ) (g kg ) (cmol c kg )
Control (without 1.0 11.07 6.4 4.78
Weeds)
Crotalaria lappacea 1.2 7.09 10.8 5.13
Asystasia gangetica 0.9 9.16 11.0 6.66

Chromolaena odorata 1.0 10.13 7.7 4.68
Widelia sp. 1.0 18.36 9.0 5.58
Imperata cylindrica 0.9 7.29 8.4 4.75
Setaria plicata 1.0 9.69 9.5 4.93
Paspalum conjugatum 1.0 7.90 9.6 5.23
Sembodo et al. (2012)

The cost for weed management and weed control comprises a significant
amount of farmer’s expenditure. Hundreds billions dollar is spent yearly for this
purpose around the world, including that for the procurement of control tools and
machines, herbicides, and other chemicals as well as for labors. In Indonesia, the
expenditure in 2006 alone for herbicide procurement amounted to 99 million euros
or about 1.4 trillion rupiahs (CropLife Asia, 2007). These figures indicate that
weeds are so important part in agriculture that they need particular attention. The
high expenditure in weed control shows that farmers concern about the negative
effects of weeds on crop production, environment, health, and natural beauty.
Weed control techniques may ecologically also affect the soil environment.
Some soil properties may be influenced by the presence or the absence of weeds.
Some chemicals employed in weed management may also directly or indirectly
affect the soil properties.

Abdul Kadir Salam and Nanik Sriyani – 2019