land

Distinctions

eretz (ארץ)

The Vilna Gaon: eretz connotes land as national settlement, and in the construct it names a particular nation's land, so "country" fits it well; an unqualified eretz often means Eretz Yisrael in particular. Malbim: eretz takes in the whole planet, from the surface down to the innermost core, while adamah is only the crust whose dirt is farmed.

The berachos put the difference on display. Over bread one says that Hashem brings forth bread min ha'aretz, from the land; over vegetables, that He creates the fruit ha'adamah, of the ground. Rabbeinu Bachaya and the Ritva: bread should by rights have taken the more specific adamah, the word for a field, and the reason it does not is that Chazal shaped the berachah on the language of the pasuk (Tehillim 104:14), which says bread comes from the eretz.

Rabbi Yechiel Michel Moravsky of Lublin answers from the meanings themselves. Adamah is limited to the immediate top layer of dirt, while eretz reaches what lies underground; wheat, whose roots run deep (Yerushalmi Taanis 1:3 puts them at fifty handbreadths), is therefore said to come from the eretz, while vegetables, which do not need such depth, are fruit of the adamah. Rabbi Yisrael Lipschitz explains similarly.

adamah (אדמה)

The Gra: adamah denotes specifically uninhabited land set aside for agriculture, against eretz as settled national territory. The Pri Megadim adds a different axis entirely: eretz is land in its supernal, unblemished state, which is why it suits the Holy Land, while adamah is the stained and imperfect ground that Hashem cursed for Adam's sin (Bereishis 3:17). On his reading the vegetable berachah says adamah because it acknowledges Hashem's kindness now, growing produce out of cursed ground, while the bread berachah looks back before the sin, when whole loaves rose from the earth, and forward to the days of Mashiach when they will again (Shabbos 30b), and so says eretz, the land that will by then break free of its curse and return to its pure, unblemished state.

the dissent

The Maharshal holds the reverse: eretz is limited to the surface and the topmost three cubits of soil (compare Rashi to Bereishis 6:13), while adamah is the more general word and takes in the depths as well. On his reading bread comes from the eretz because grain shoots up out of the surface, and vegetables are of the adamah because they draw their nourishment from deeper down. Rabbi Yitzchok Dov Bamberger, the Wurzburger Rav, follows him.

the word-switch at Korach

The Torah moves between the two words as the ground opens under Korach: Moshe warns that the adamah will open its mouth, the adamah under them splits, and then the eretz opens its mouth and swallows them, and the people flee lest the eretz swallow them too (Bamidbar 16:30-34). Where the episode is recalled it is the eretz that swallowed them (Bamidbar 26:10, Devarim 11:6). Rabbi Yaakov Chaim Sofer, Rosh Yeshivah of Yeshivas Kaf HaChaim in Yerushalayim, works from the distinction above: the opening came in two stages, the surface layer first and then the subterranean depths, and the switch of words records it.

Rendering guidance

• Eretz: land, or country where a nation's territory is meant, or earth where the whole world is (shamayim va'aretz). Eretz Yisrael stays as it is.
• Adamah: ground, or soil where farming is in view. "Land" for adamah should be reserved for the idiom "the face of the earth."
• Adam min ha'adamah: keep the echo. Where a passage builds on man being taken from the adamah, "ground" preserves it and "earth" muffles it.
• Trap: English "earth" absorbs both words outright, and "land" absorbs both nearly as well. At Bamidbar 16:30-34 the entire question is why the pasuk switched, so the English must switch too: "ground" for the first stage, "land" for the second.
• Trap: do not carry one commentator's scale of breadth into another's passage. The Gra and the Maharshal are opposed on which word reaches deeper.

Sources

Rabbi Reuven Chaim Klein, "The Land Down Under," What's in a Word?, Ohr Somayach, 30 Sivan 5777 (2017-06-24): raw text in sources/whats-in-a-word/raw/7313-the-land-down-under.md. Primary loci: Bamidbar 16:30-34, 26:10; Devarim 11:6; Tehillim 104:14; Bereishis 3:17; Rashi to Bereishis 6:13; Yerushalmi Taanis 1:3; Shabbos 30b; the berachos of hamotzi lechem min ha'aretz and borei pri ha'adamah.