• It would appear that Rhotwyda is knowledgeable about blackloam. Seek her in the orchard and ask her about this special soil.
• While Rhotwyda knows where blackloam may be found, she refuses to do the obtaining herself. In her stead, gather three bushels of blackloam from the lair of aurochs known as the Cookpot.
• You have obtained the required quantity of blackloam. Deliver it to Pfrewahl at Tiller's Rest.

Pfrewahl is overjoyed upon seeing the blackloam, but becomes coy when you express your curiosity at the soil's origins. Hopefully it is nothing to soil oneself over.

• Talk to Gurcant and accept the quest.
• Head west and speak to Rhotwyda
• Head west to The Cookpot and interact with three Blackloam
• Hand the Blackloam to Pfrewahl at Tiller's Rest to complete the quest.