Minecraft wiki entry for Tips_and_tricks, associated text: When starting out, you can speed up wheat or other crop growth by planting in alternate rows, with empty farmland or a different crop between. However, once you've gotten to the point where you can plant a whole field in one crop, the speed isn't really worth the trouble of mixed crop, as it's easier to use a water bucket to harvest the whole field at once, and it's quickest to replant the field in a single crop.