Often you may have several weeds in your pasture (or other places) that you would like to control. For a few plants it might be easy to pull them out by hand, but for others chemical control may be a preferable option. But an important aspect to weed control is that in good, healthy soils pasture is often able to outgrow weeds. If you have poor, acid and compacted soils, you will have weeds, regardless how much you dig out and spray.
First you need to know what you are looking at. I have provided pictures of some of the more common weeds you may find in your paddocks. One thing you have to be aware of is that plants may look different at different stages of growth. Ragort for instance may look a little bit like a dandelion when young, just a small rosette of leaves low to the ground. This is the best stage to spray at. But when older they may have flowerspikes up to two meters high with lots of yellow flowers. This is the stage when a ragwort infestation becomes most obvious, but much harder to control. While pulling out by hand may seem easy, often small roots are left behind which may grow into multiple new plants. Do your research or seek advice before doing anything which could possibly make things worse or cause other problems.
For the weeds for which I have provided pictures I have developed a chart which cross references to some of the more common herbicides. The chart may make it easier to select a suitable chemical. As with all chemicals it is vital to read the manufacturers instructions as there maybe specific stock withholding periods, or special licences may be required or the chemicals are only suitable at certain times of the year or stage of plant growth. Anyway, take care.