The first two lines of the poem are its most vague, and in turn, the most suggestive. The lines are a mysterious cliffhanger: so much depends upon... what exactly? In this moment, it could be anything; four short words open up endless possibilities.
The poem's form reflects this mystery—with the enjambment creating a sense of anticipation as the poem begins to spill down the page, each line depending on the following in order for its full meaning to become clear.
The language, meanwhile, creates a casual, calm tone. For one thing, there is no capitalization or punctuation whatsoever. The speaker is not concerned with following strict grammatical rules, and keeps the initial "s" lowercase despite the fact that this is the start of the poem's single sentence. The poem's lack of capitalization contributes to the speaker's tone, creating an atmosphere of detached observation rather than urgent judgment.
The language in this first stanza also demonstrates the gentleness that pervades "The Red Wheelbarrow." The first line does indeed make a declaration, asserting that "so much depends / upon" something (soon revealed, of course, to be a red wheelbarrow), but this declaration is far softer than it could be. Think of it this way: if the speaker instead announced, "My life depends on my red wheelbarrow," the poem would then be decidedly more urgent! It could very well be that the speaker's life depends on this wheelbarrow, but the phrasing and grammar soften the line's impact. This is a poem concerned with reflection, not drama; with creating an image, not relaying a plot.
The first two lines also contain both assonance and consonance: with the short /u/ sound (which sounds like, "uh") in the words "much" and "upon," as well as the /n/ and /p/ sounds in the words "depends" and "upon," respectively. The /u/ sound is also somewhat similar to the short /e/ sound ("eh") in the word "depends." This creates a sense of internal cohesion, the first line sonically connected to the second—even if the reader is not yet sure why.