Once all your fruit has been harvested, you have an opportunity to improve your soil fertility. Some nutrients are not very mobile in the soil. This list includes P, K, Mg, Ca, Fe, Mn and Zn. That means you can safely apply them in the fall without the fear of losing them to leaching loss when the heavy rain comes down later. Now, this doesn’t mean you should avoid applying them in the spring, especially if you know you have a deficiency of one or more. However, there are times when you simply cannot get all the nutrients that you need, applied in the spring. In particular, potash and magnesium are two common nutrients that can be fall-applied. If your recommendations are to apply a high volume, why not split the application; some in the spring and some in the fall. After harvest, once you have weeded, tucked in the canes, or other operations, then relax and zip up and down the rows, squirting in that little bit extra K and Mg, if you need them. As necessary, you can ask for a blend containing both, and include your humic acid or other ingredients too, all at the same time.