In the original manuscript, Oliver Cowdery initially started to write also a second time in this passage (that is, he almost created a dittography for the word also). He wrote the initial als but apparently not the letter o; then he erased most of the l and all of the s and overwrote the erased portion with the initial p of the following word, plenty. The corrected reading in 𝓞 definitely reads a plenty, but it is possible that the original text itself read plenty rather than a plenty—in other words, the a was simply the initial a of also left accidentally unerased.
This interpretation of 𝓞 could be used in support of the 1981 LDS emendation, where a plenty was replaced by plenty. This emended reading, of course, is what modern English readers expect. Furthermore, it agrees with one other instance of plenty in the text: “our women did give plenty of suck for their children” (1 Nephi 17:2). Nonetheless, there is one other instance where plenty takes the indefinite article:
In this case, the use of the indefinite article seems required. But this last example also suggests that the use of a plenty in Alma 57:6 is intended.
We can find ample support for a plenty in earlier English, beginning with the following example from John Wycliffe’s 1388 translation of the Bible:
Here the accidentals are regularized in accord with W. R. Cooper’s transcription on page 446 of The Wycliffe New Testament (London: The British Library, 2002). This example, with its adjective, seems to require the indefinite article, like the example in Helaman 6:9. But under definition 2b of the noun plenty, the Oxford English Dictionary lists a number of examples of a plenty of with the meaning ‘an abundance of ’ (again accidentals are regularized):
Literature Online has a couple of examples of the specific phrase “a plenty of provision(s)”, both dating from the 1600s (once more the accidentals are regularized):
There is no reason, then, for considering “a plenty of provisions” an unacceptable reading in Alma 57:6. The critical text will restore this instance of the indefinite article.
The 1981 change from a plenty to plenty may have been prompted by a list of problems in the LDS text vaguely identified by Paul Cheesman on page 163 (Appendix 1) of his book The Keystone of Mormonism: Little Known Truths about the Book of Mormon (Salt Lake City, Utah: Deseret Book, 1973). We cannot be sure what Cheesman actually meant since for each problem he lists only the chapter and verse without actually identifying what the problem is except to categorize the problem as related to grammar, usage, spelling, meaning, punctuation, or construction—or as a redundancy, excess word, or archaic word. Here under Alma 57:6, Cheesman was apparently worried about the indefinite article a before plenty since he claims there is an “excess word” in this verse. The a before plenty appears to be the only possible “excess word” in this verse; in current English, readers expect “plenty of provisions” rather than “a plenty of provisions”. The editors for the 1981 LDS edition may have followed Cheesman’s suggestion here. It is worth pointing out, though, that the 1981 edition implemented no substantive textual changes based on any of the other problematic passages listed by Cheesman (although there is the 1981 change of the spelling plead to pled in Alma 22:20 that may have come from Cheesman’s list). In general, the 1981 edition avoided the editing out of other unusual instances of the indefinite article a, as in the following two examples that were left unchanged in the 1981 edition (and were also not listed by Cheesman as problematic):
Since the editing for the 1981 edition was very carefully controlled, it appears that the omission of the a from a plenty was fully intended rather than being a typo.
Summary: Restore the original indefinite article a before plenty in Alma 57:6 (“a plenty of provisions”) since such usage can be found in earlier English.