Direct drilling comes in two guises; drilling after a little cultivation (“min till” really), and what in the USA would be called “zero till”. Each has its own consequence in terms of weed control. Maybe I learned, years ago, most from a farms manager called Richard Noyce, he always had clean bottoms to his crops simply because, after harvest, he cultivated the surface several times to get weeds seeds to germinate, before putting the next crop in. The alternative of one pass to put the crop in does imply more work to do with selective herbicide – but that is probably going to happen anyway, so it is not an extra cost. Generally, in the hands of a sensitive husbandry man, zero till costs less and gives higher yields.
Bill Butterworth, Land Research Ltd, 20 August ‘18