I'm not doing it for the farm ... probably a good idea now that I ponder on it ... but have something similar for the church  Someone is always saying "Well, when did we?" or "How much did we?"  I keep a running record of "significant actions" and another listing special speakers and groups, when they were here and what we paid them.  I just print it out every few  months and put the latest version in my folder with meeting minutes.

Sometimes the solution is not elegance.  Start writing it in a word processor document. Just open it and start writing new entries at the top and save it when you are done

When you want to find something you can scroll down and search by date or use the search function on your word processor to find key words. Depending on details you could have one document per year or month or week, or one big one that goes on forever.

You could also set up a database that sorts by fields but that takes more organization and discipline.  The text document is much more free style.

For instance:

2010 - 6 - 25  finished corn planting 5th time.  Going fishing.

2010 - 6 - 1  finished corn planting 4th time. FINALLY! 

2010 - 5 - 6  finished corn planting 3rd time.  Sure glad replant corn is free. 

2010 - 4 - 27  finished corn planting 2nd time.  Little muddy, and was raining when we finished. 

2010 - 4 - 10  finished corn planting.  Was raining when finished.

If you have one per year the 2010 could be left off.  If you want to write a daily diary type of entry it's no big difference, just more words