No land shall be patented to any person under sections 321 to 323, 325, and 327 to 329 of this title unless he or his assignors shall have expended in the necessary irrigation, reclamation, and cultivation thereof, by means of main canals and branch ditches, and in permanent improvements upon the land, and in the purchase of water rights for the irrigation of the same, at least $3 per acre of whole tract reclaimed and patented in the manner following: Within one year after making entry for such tract of desert land as aforesaid the party so entering shall expend not less than $1 per acre for the purposes aforesaid; and he shall in like manner expend the sum of $1 per acre during the second and also during the third year thereafter, until the full sum of $3 per acre is so expended. Said party shall file during each year with the officer designated by the Secretary of the Interior proof, by the affidavits of two or more credible witnesses, that the full sum of $1 per acre has been expended in such necessary improvements during such year, and the manner in which expended, and at the expiration of the third year a map or plan showing the character and extent of such improvements. If any party who has made such application shall fail during any year to file the testimony aforesaid the lands shall revert to the United States, and the 25 cents advanced payment shall be forfeited to the United States, and the entry shall be canceled. Nothing herein contained shall prevent a claimant from making his final entry and receiving his patent at an earlier date than hereinbefore prescribed, provided that he then makes the required proof of reclamation to the aggregate extent of $3 per acre: Provided, That proof be further required of the cultivation of one-eighth of the land.