account_interest_line/view/account_payment_term_view.xml

<?xml version="1.0" encoding="utf-8"?>
<openerp>
  <data noupdate="0">

    <record id="view_payment_term_line_tree" model="ir.ui.view">
      <field name="name">account.payment.term.line.tree</field>
      <field name="model">account.payment.term.line</field>
      <field name="inherit_id" ref="account.view_payment_term_line_tree"/>
      <field name="arch" type="xml">
        <field name="days2" position="after">
          <field name="interest_rate"/>
        </field>
      </field>
    </record>
    <record id="view_payment_term_line_form" model="ir.ui.view">
      <field name="name">account.payment.term.line.form</field>
      <field name="model">account.payment.term.line</field>
      <field name="inherit_id" ref="account.view_payment_term_line_form"/>
      <field name="arch" type="xml">
        <xpath expr="/form/group/group[1]" position="inside">
          <field name="interest_rate"/>
        </xpath>
      </field>
    </record>
  </data>
</openerp>