Multiple harvests, better utilization of labor, eliminating the risk of bad late season weather wiping out your crops... I think doubling the net yield is a conservative estimate.
Ah, but that is, again, just playing into how much yield per land we are getting. What we need to know is how much workforce we need to actually sow and harvest all that. The real work.
I meant per unit of labor. I think the improvement relative to land area would be even greater. 100x growth rates mean you could potentially harvest one plot of land every day or two.
We've achieved that kind of result in the real world just by introducing herbicides.
As far as I am aware, the major point was actually harvesting machines, in terms of labor force savings. But in our example, no such machines are available.
There are many, many advances that have improved agriculture yields, you can't just pick out one and think that is the whole story.
http://africarice.blogspot.com/2012/11/creating-awareness-on-labor-saving.html
"Weeds are one of the major constraints to rice production in sub-Saharan Africa. Without control, they can cause yield losses ranging from 28% to 89%."
https://pesticidefacts.org/perspectives/herbicides-reduce-hand-weeding-in-africa/
"The majority of African farmers identify weeds as a major problem with yield losses, which can range from 25 to 100 percent."
"These hand-weeding methods account for 50-70 percent of production labor."
https://croplife.org/case-study/herbicide-use-in-africa-would-lead-to-large-increases-in-crop-yields/
"Research with herbicides has resulted in yield increases of up to 55% in maize and 75% in cotton. "
https://www.iita.org/news-item/novelty-weed-control-method-boosts-ssa-women-cassava-farmers/
"Research has shown that weeding takes 50% to 80% of the total labor budget of cassava growers"
https://www.tandfonline.com/doi/full/10.1080/00220388.2020.1786062#
This article discusses the poverty ramifications of herbicides displacing labor.
"Altogether, these households hired 65% less labour for weeding and banking when they used herbicides (n = 46)."
The exact numbers are going to vary depending on the crop, climate, etc. This is not a systematic survey, just trying to find examples that are not in the context of modern mechanized agriculture.
That's all about weeds which require labor, but rapid growth also defeats plant blights and pests. If you grow your entire crop in 1-2 days, there's much less opportunity for them to get eaten by pests.
https://link.springer.com/article/10.1007/s13593-012-0105-x
"Globally, an average of 35% of potential crop yield is lost to pre-harvest pests"
In the real world, herbicides and pesticides also cost labor, are imperfect, and have health ramifications. But here we eliminate the need for them entirely, and by making our farmers Druids they also have access to healing spells, purification spells, etc, so the overall health picture improves too (which also improves the efficiency of labor since people are out sick less).