Agricultural Theurgy

Food Crops
Theurgy is used across the Hegemony to accelerate the growth of food grains, bringing enough harvests to sustain a larger population that our world achieved until modernity. However, there are indications that this is ultimately unsustainable, exhausting the soil over time, so incrementally more blood is required every year to bring the same yield.

"It’s possible to do Theurgic farming more sustainably than at present–but the science of it is poorly understood, because for so long the Hegemony has been enjoying a blood surplus that meant it could ignore the limitations of their current agriculture model with e.g. just a bit of crop rotation.

"It will take either a whole lot more blood or many years of soil repair to fix the problem–and the solution needs to be done at a large scale to avoid starvation. You’ll also need a lot of landowners to convert from commercial cash cropping back to food." (source)

Dyes
The Valley of Dyes in Karagon is full of Theurges continually breeding new dye-plants, with colors never yielded by nature. (Though they've yet to reproduce the rich notteco dye, made from a plant that grows only in the far southern reaches of Abhuman territory.)

Mullow and Shrub Yam
The herb mullow was carefully bred by Theurges to sedate the homunculi in both male and female seed, As both homunculi are needed to unite into a new human being, either a man or a woman can chew mullow and prevent conception. The effects of chewing a few dried leaves lasts about a week. The shrub yam, helots' primary food, was tweaked to have the opposite effect, and helots are forbidden to eat mullow. Mullow grows wild across Shayard, though rather less so in higher or dryer areas; many yeomen families do well gathering and selling it to traders.