For additional information regarding the effects and use of fertilizer, see farming. If the crop itself is already gold-quality, this benefit will simply be added to the return, or 4 extra produce and seeds total.
The quality of the grapes will affect the quality of the products made from it.
Grapes are an improvable crop, meaning they have a variety of quality levels and can be improved upon with fertilizer. With quality crops, the produce and seeds will be increased by 2, as well as guaranteeing 2 upgraded produce and seeds. Grapes are a type of crop which can be grown from grape seeds in the vineyard. With basic crops, the produce will be increased by 6 and the seeds will be increased by 3. In regards to Quality fertilizer II specifically, the given crop's return on average will be improved significantly. The benefit of a 'Quality' fertilizer - note the star icon - is an overall improvement to a crop's yield. Like all fertilizers, a single unit may be applied to a single farming plot - either an empty garden bed, garden bed with sticks, or vine trellis - in order to provide a benefit to the subsequently planted crop.
Quality fertilizer II is produced at the Church workbench by combining the basic fertilizer peat with two flavor enhancer, the latter requiring advanced alchemy.
