What are immovables by incorporation?

Immovables by incorporation are those which are essentially movables but are attached to an immovable in such a way as to be an integral part [especially par. 2, 3, 4, 6 & 7 of Art. 415 of the Civil Code].

[1] Trees and plants are only considered immovables when they are attached to the land or form an integral part of an immovable. Hence, uprooted trees and plants are not immovable.
[2] When trees have been cut or uprooted, they become movables. However, Manresa holds the view that uprooted timber is still immovable because of the purpose of a timberland.
[3] By special treatment of Act 1508 (Chattel Mortgage Law), growing crops may be subject of a Chattel Mortgage.
[4] For the purpose of attachment, growing crops are to be attached in the same manner as realty. According to De Leon, under the rules on attachment, growing crops may be treated as personal property.
[5] "Everything attached to an immovable in a fixed manner, in such a way that it cannot be separated therefrom without breaking the material or deterioration of the object." (Res vinta in Roman Law)
[6] “Attachment in a fixed manner" means that breakage or injury in case of separation will be substantial, e.g. that caused on wells, sewers, aqueducts and railways.
[7] "Attachment in a fixed matter" does not require that the thing has been attached by the owner himself or some other person.
[8] "Fertilizer actually used on a piece of land" is immovable. "Actually used" means that it has been spread over the land.