Knight Farm Machinery trailed sprayers: When Brian Knight built his first 2,000-litre, 12m boom trailed sprayer back in 1984, he fitted it with a mechanical tracking drawbar. Twenty years on, there has been a whole raft of further drawbar and other developments. If looking for a machine from the interim, the key to ‘used’ success is finding a model of the optimum spec, as James de Havilland reports