25 CFR §162.223

1. (a)Except as provided in paragraph (c) of this section, an agricultural lease must provide for one or more rental adjustments if the lease term runs more than five years, unless the lease provides for the payment of:
   1. (1)Less than a fair annual rental, as permitted under § 162.222(b) through (c) of this part; or
   2. (2)A rental based primarily on a share of the agricultural products generated by the lease, or a percentage of the income derived from the sale of agricultural products.
2. (b)If rental adjustments are required, the lease must specify:
   1. (1)How adjustments are made;
   2. (2)Who makes the adjustments;
   3. (3)When the adjustments are effective; and
   4. (4)How disputes about the adjustments are resolved.
3. (c)An agricultural lease of tribal land may run for a term of more than five years, without providing for a rental adjustment, if the tribe establishes such a policy under § 162.203(b)(4) and negotiates such a lease.