Normally the text refers to “the lands of our possessions”. Nonetheless, the singular land is possible; see for instance the discussion under 2 Nephi 9:2 regarding the related phrase “the land(s) of one’s inheritance”. Similarly, the singular possession is generally possible, as discussed under Alma 22:33–34. For specific discussion of the phrase “the land(s) of one’s possession(s)”, see under 2 Nephi 29:14 and Helaman 5:52. Here in Helaman 7:22, the critical text will maintain the reading of the earliest extant text, “the land of our possession” (the reading in 𝓟).
Summary: Maintain in Helaman 7:22 the earliest extant reading, “the land of our possession”; usage elsewhere in the text allows for the singular land and the singular possession in this phrase.