Christmas tree cultivation has shifted toward the production of higher-quality trees, increasing land quality expectations as well. Indeed, some species of tree, such as the Fraser fir, are unable to grow on low-quality, marginal farmland. Flat or gently rolling land is preferred to that with steep slopes and inclines, which is prone to erosion and fluctuations in fertility. Noticeable obstructions, such as rocks, fences or significant underbrush, are also undesirable. Like all crops and plants, Christmas trees require a specific set of nutrients to thrive. There are 16 elements crucial for growth; of those, three are obtained through air and water: hydrogen, carbon,
Thai royal and noble titles a courtesy title pronounced with a middle tone, should not be confused with the similarly-spelled tree or the feudal title of Khun (, pronounced in a rising tone). The courtesy title is used for children born to a noble mother who gave up her title to marry a man of lesser rank; a notable example was the late Khun Poom Jensen. Today, this word is used informally to courteously address nearly anyone except those who hold a title of Mom Rajawongse or higher. It is T-V distinct from "thoe" (). Thai royal and noble titles Thai royal and noble titles