Using herbicides to kill weeds
Glyphosate is the main herbicide used to kill almost any plant. It is sprayed onto the plant's leaves. A major glyphosate herbicide is Roundup® (for commercial and agricultural use), but there are many other glyphosate products on the market.
Glyphosate has some advantages over other herbicides. Although glyphosate dissolves well in water, it sticks to soil particles. The soil itself could be washed into river systems, but the glyphosate would end up in the aquatic sediment and not in the water.
Because it binds to soil, glyphosate does not leach into groundwater or poison crops through the roots. Glyphosate is also much less poisonous to animals (including humans) than many other herbicides. Microbes break glyphosate down relatively quickly, so the herbicide does not remain in the soil for long periods of time.
However, glyphosate can kill all the plants it falls on – both crops and weeds.
A number of other herbicides are also available to farmers; for example, atrazine, glufosinate or bromoxynil. Farmers may spray their crops with at least two different herbicides, because some weeds may be tolerant and survive the spraying with the first herbicide. Those weeds are often killed by the second or third spraying with a different herbicide.