Seeding into heavy residue may be a problem for some drills. For example, seeding canola into barley stubble at V2 with a ZT disc drill. There may be problems with hairpinning. Another factor may be fertilizer placement. Inherent with direct seeding is the need to precision band fertilizer away from the seed.
Seed placed fertilizer is risky especially with crops such as canola and flax.
With sensitive crops a better choice may be to broadcast the fertilizer. It may be an advantage to use a heavy nutrient and moisture user following a less nutrient taxing crop. In the case of a legume crop or perhaps a forage crop such as alfalfa, nitrification may take place for two years allowing for two successive crops of heavy nitrogen users following these crops. Fertilizer inputs should still be used, but perhaps at a reduced rate. In areas of moisture restrictions, it may be necessary to alternate heavy water users with crops not as demanding.