I think I've seen this same issue in my last ice sheet colony. Takes a very long time to fertilize a whole growing area.

I love this mod, but this is one thing that absolutely drives me mad. I usually have 3-5 large sowing areas (around 150-250 tiles) and can finish sowing 1 of the areas by 1pm. I then have to make 3 workers work overtime usually until at least 3am in the morning if I want them to finish in "the same day". Why can't they pick up a big sack of biosolids as if they were hauling and then fertilize an area of land like if they were laying down the blueprints of power conduits with steel. Imagine if you had a backyard garden and a large sack of fertilizer in your garage, 40 feet away at the front of your house. Do you run back and forth using a tiny spoon to transfer it ,or do you just grab the whole freaking sack and divvy it amongst the garden all at once. Sorry if this sounds hostile, but it's literally the only gripe I have with this mod. This is a first-rimworld problem, but man it would be such a blessing.