In addition to the powers and authority, and including districts organized for the purpose of cooperating with the government of the United States under the terms of the federal reclamation law and other federal laws now vested in irrigation districts organized and existing under the laws of New Mexico, irrigation districts, through their respective boards of directors are hereby authorized and empowered to borrow money upon the income, credit and assets of such district and pledge the credit, income and assets thereof to secure the same, provided that no such loan shall exceed the sum of thirty dollars ($30.00) per acre for each acre of irrigated land within such district; if said loan exceeds one thousand dollars ($1,000) the same shall be authorized or approved in writing by landowners who own in excess of fifty-one percent of the lands irrigated and assessed by the district for district purposes, as such ownership and acreage be shown by the records of such district as certified by the secretary and president of said district and which said certificate or certificates shall be considered sufficient and conclusive as to the amount of such total irrigated acreage, and of the assent of the landowners authorizing or approving such loan; and after securing the said approval in writing of the landowners, the board of directors of any such district making any such loan is hereby authorized and empowered to execute, make and deliver, in the name of and for and on behalf of such district, notes, debentures, mortgages or pledges, or other form of obligation as shall by the board of directors be deemed for the best interest of such district.