Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
pastĭno, āvi, ātum, 1, v. a. [pastinum], to dig and trench the ground, to prepare the ground, for the planting of vines: pastinandi agri rationem tradere, Col. 3, 13, 6; 11, 3, 9: solum, Plin. 17, 21, 35, § 159: vineas, id. 18, 26, 65, § 240: pastinatae vineae, id. 14, 1, 3, § 14; Vulg. Marc. 12, 1.
Hence, pastĭnātum, i, n. (sc. solum), ground dug and trenched; ground prepared for planting the vine, Col. 3, 13, 7: vineam in pastinato serere, Plin. 17, 22, 35, § 172; Col. 3, 3, 11: umidum pastinatum, id. 3, 16, 1.