Oh, and one more thing! -- Cleaning Crops:
Some crops can be termed "cleaning crops" because they can be kept weed free fairly easily. Examples are squash and potatoes. Potatoes because when you hill them you are disturbing and killing weeds anyways, and squash because they can be weeded easily until they vine out and smother weeds with their vines. On the other hand, root crops such as onions, beets, carrots, turnips, and such are great examples of crops that are much harder to keep weed free.
The advantage to growing a cleaning crop is that with good weed control one year you should have less weed pressure the next. So if you grow a cleaning crop one year and then another crop which is harder to keep weed free the following year, you can benefit from less weed pressure during the time you grow the crop that is harder to weed anyways.
Make sure to mark that on your 3x5 cards too! 🙂