Nec tantum segetes alimentaque debita diues
poscebatur humus, sed itum est in uiscera terrae;
quasque recondiderat Stygiisque admouerat umbris,
effodiuntur opes, inritamenta malorum.
Nec tantum segetes alimentaque debita dives
poscebatur humus
This is syntactically somewhat interesting. It’s the passive of a double accusative construction, which occurs with this verb.
L&S posco:
With a double acc.: parentes pretium pro sepulturā liberum poscere, Cic. Verr. 2, 1, 3, § 7: magistratum nummos, id. ib. 2, 1, 17, § 44: aliquem causam disserendi, id. Tusc. 3, 3, 7: claves portarum magistratus, Liv. 27, 24, 8: non ita creditum Poscis Quintilium deos, Hor. C. 1, 24, 12: cur me in decursu lampada poscis? Pers. 6, 61: poscenti vos rationem, Vulg. 1 Pet. 3, 15.—Hence, pass.: poscor aliquid, I am asked for something, something is asked or demanded of me (poet. and in post-class. prose): gravidae posceris exta bovis, they ask you for the entrails, Ov. F. 4, 670; cf.: poscor meum Laelapa, they demand of me my Lœlaps, id. M. 7, 771: nec tantum segetes alimentaque debita dives Poscebatur humus, id. ib. 1, 138: quod rationem pecuniae posceretur, Gell. 4, 18, 12; to be called upon or invoked to inspire a poet or to sing: aversus Apollo Poscitur invitā verba pigenda lyrā, Prop. 4 (5), 1, 76 (better reading poscis ab); cf. absol. Palilia poscor: Non poscor frustra; si favet alma Pales, Ov. F. 4, 721; so, poscimur Aonides, Ov. M. 5, 333: poscimur, Hor. C. 1, 32, 1.—
http://perseus.uchicago.edu/cgi-bin/philologic/getobject.pl?c.14:3896.lewisandshort
"Not only was the rich earth required [to produce] crops [here, the crops, not the fields] and [rightfully] owed food . . . ", “Not only were grain and rightfully owed food demanded of the rich earth . . .”
The passive of eo is impersonal, as you recognize. From somewhere Aeneid 6: itur in antiquam siluam.
quasque recondiderat Stygiisque admouerat umbris,
effodiuntur opes, inritamenta malorum.
Once again, a relative clause quas[que] recondiderat Stygiisque admoverat umbris, comes before its grammatical antecedent, opes.
But your problem here (and I don’t mean to be a scold) is that you didn’t look up recondo in the dictionary. It doesn’t mean “re-found” – it means “store away” or “hide away.” Opes is plural and can’t be the subject of the recondiderat and admouerat, as you recognize. The subject is humus.
“and the resources which it had hidden away and moved to the Stygian shades [a poetic expression for “the underworld”] were dug up–incitements to evil deeds.”
I think malorum is probably neuter, not masculine, but I could be wrong.
Incidentally, “store away” is among the meanings of the base verb condo.
L&S:
II With the access. idea of carefulness, to put away, to lay, put, or place somewhere for preservation, etc.; to lay up, store or treasure up (opp. promo).
A In gen. 1 Prop. (a) Aliquid: pecuniam, Cic. Clu. 26, 72: frumentum, id. N. D. 2, 63, 157; Hor. Ep. 2, 1, 140: condere et reponere fructus, Cic. N. D. 2, 62, 156: agri multa efferunt, quae … mandentur condita vetustati, id. ib. 2, 60, 151; cf. id. Brut. 4, 16; Varr. R. R. 1, 62; Auct. B. Afr. 65: vinum, Varr. R. R. 1, 13; cf. Mart. 13, 111, 2; Verg. E. 3, 43; Hor. Ep. 1, 1, 12: aliquid proprio horreo, id. C. 1, 1, 9: Sabinum testā levi, id. ib. 1, 20, 3: pressa mella puris amphoris, id. Epod. 2, 15: messem, Tib. 1, 1, 42: fruges, Paul. Sent. 2, 8, 2.— (b) With the designation of the place (most freq. by in and acc.): minas viginti in crumenam, Plaut. Truc. 3, 1, 9: mustum in dolium, Varr. R. R. 1, 65, 1: cineres in urnas, Suet. Calig. 15: barbam in auream pyxidem, id. Ner. 12; cf. id. ib. 47: legem in aerarium, id. ib. 28: libri in sacrarium conditi, Gell. 1, 19, 10; cf. the foll.: te in pistrinum, Plaut. Ps. 1, 5, 120; cf.: aliquem in custodiam, Liv. 31, 23, 9; Tac. H. 4, 2: aliquem in carcerem, to thrust into prison, imprison, Cic. Verr. 2, 5, 29, § 76; Liv. 26, 16, 6; 29, 22, 7; 30, 21, 5; 45, 42, 5: aliquem in vincula, id. 23, 38, 7; 26, 34, 4. —With adv.: argentum intro, Plaut. Ps. 1, 3, 120; id. Truc. 5, 28: sortes eo, Cic. Div. 2, 41, 86 Orell. N. cr.—With in and abl.: litteras publicas in aerario sanctiore, to keep, lay up, Cic. Verr. 2, 4, 63, § 140: se (aves) in foliis, Verg. G. 4, 473: novissimo die dein (argyritin) condunt in plumbeo vase, Plin. 33, 6, 35, § 109.—With abl.: condidit (libros Sibyllinos) duobus forulis auratis sub Palatini Apollinis basi, Suet. Aug. 31; Scrib. Comp. 145.—With locat.: id domi nostrae, Cic. Verr. 2, 2, 2, § 5; cf.: ut ei jam exploratus et domi conditus consulatus videretur, i. e. he was sure of it, id. Mur. 24, 49.— 2 Trop.: teneo omnia; in pectore condita sunt, Plaut. Ps. 4, 1, 31: mandata corde memori, Cat. 64, 231: tu, qui omne bonum in visceribus medullisque condideris, Cic. Tusc. 5, 9, 27: in causis conditae sunt res futurae, lie, are contained, id. Div. 1, 56, 128.
http://perseus.uchicago.edu/cgi-bin/philologic/getobject.pl?c.2:4113.lewisandshort