It is important to remember that the soil must be parameterised for the crops that you're going to sow. If your simulation is going to sow wheat, then the soil must have LL, KL and XF values for wheat.
If the soil you wish to use does not have these values for the crop you desire, then you can add them.
Start by clicking on the soil component in your simulation tree, make sure the Water tab is selected, then right click anywhere on the table. Click the "Manage crops" pop up.

In the window that appears, click the green plus symbol "+" button to add a new crop.

Type in the name of the new crop that you wish to add. (nb. It must match the name of the crop component that you are going to drag onto the simulation tree exactly). Click OK.


In the Water tab you should now see that your new crop has been added with default values filled in for LL, PAWC, KL and XF. (You may have to use the horizontal scroll bar along the bottom of the table to view your crop. Depending on what order you specified when you added it)
The table is editable so you may change any of the values in the table. Including those of other crops, SO BE CAREFUL.

Once you have changed the values for LL, PAWC, KL and XF to what you want, you are done. You can now continue building the rest of your simulation or do a run.
Note, you can copy and paste these values from other crops by selecting all the cells you want to copy with the mouse, and then pressing "Ctrl + C" and then clicking on the top cell of the LL column for the new crop you have added, then pressing "Ctrl + V".
You can find out more about LL, PAWC, KL and XF in the Science Documentation for Soil.