(lessors of farmland failed to perfect interest in lessee’s government payments; bank did perfect interest in government payments and applied payments to balance of loan owed by lessees that declared bankruptcy; lessors did not receive full rental payments before lessee filed bankruptcy; lessors sued the bank claiming a superior lien in government payments and that a constructive trust existed because bank had knowledge of leases, so payments should have come to lessors; district court granted summary judgment in favor of bank; appellate court affirmed holding no constructive trust existed because there was no confidential relationship between bank and lessors).