I have 5 farming, and the The Will to Power skill, but Yeomanry doesn't appear on my skills list for purchase? Would someone please explain to me the requirements for it?
And I'd like to know if I can use mulberries or blueberries to "plant grass," and how to get the option to plant grass?
There is a farming skill like the skills hunting and foraging which is not the same as having a skill level in farming. If you get farming you will be able to access yeomanry and plant grass. Farming costs 400 lp.
To plant grass you need seed. To get seed you need to find wild windsown weed (it looks like a white feather) which can first be seen when your exploration is at 8. You dry the www on either a drying rack or an herbalist's bench. It will turn into some sort of planting product. You can't use hop cones or onions for grass seeds but the other products: tea, wheat, flax, poppies, hemp etc can be put onto either ploughed or paved ground using the planting grass option from the Adventure>Landscaping menu.