Page 61 - Ilmu Tanah

48 The Chemistry and Fertility of Soils under Tropical Weeds

these methods need limited control employing other methods of weed control or
may not need other method of weed control due to the limited and insignificant
weed population.

Mechanical and Physical Control of Weeds

The principles of mechanical and physical weed control is to destroy or to
eliminate the physics of weeds with the objective to kill or inhibit the growth and
propagation of weeds (Sriyani, 2010). This method has been so popular for
centuries and is a common practice for farmers and plantation. It is popular
because this method is the easiest and probably relatively cheap and the result is
fairly instant. Included in this method are hand weeding or foot-stepping, weeding
with some tools like blade, shovel, hoe and cutting machines, weed burning or
flooding, as weel as soil tillage.
However, even though popular and easy for farmers, this method shows
some weaknesses, among which it may destroy crop rooting system and may ease
the soil erosion. If conducted with tractors or machines with weed cutters, this
method may also cause soil compaction, particularly if conducted with high
frequences for a long time. Weed burning may also cause air polution and of
course exhaust the soil carbon pools. Other weakness of this method is that weed
may quickly regrow particularly those with really short life cycles like alang-alang
(Imperata cylindrica) and Asystasia sp. and weeds that produce abundance seeds
like Ageratum conyzoides. Sriyani (2010) reports that the growth of weeds 8 weeks
after controlled with this method (weed clearing) regrow much faster that those
controlled with herbicides.

Biological Weed Control

Using this method, weeds are controlled by employing natural enemies of
weeds. This method works based on the understanding that every organism has its
own enemy in its original habitat to maintain its population equilibrium. In general
researchers agree that in its new habitat any plant tends to become weed because
plant grows and propagates relatively quickly and dominates, and then disturb the
new ecosystem. In addition due to their fast gowth, the ability of weeds to
dominate new habitat is also caused by the absence of its natural enemy.

Abdul Kadir Salam and Nanik Sriyani – 2019