"Add to cart" minimum order quantity
If you want to alter the cart item, then you can use hook_uc_cart_alter of ubercart.


  This is called every time the cart is rebuild (e.g. when products are
  added), so it's a good place to alter the cart item.


Code snippets to modify the qty of the item

/**
 * Implements uc_cart_alter.
 */
function mymodule_uc_cart_alter(&amp;$items ) {

  foreach ($items as $index =&gt; $item) {

   //you can add condition for your product

    $items[$index]-&gt;qty = 2;
  }
}


For reference:

http://www.ubercart.org/docs/api/hook_uc_cart_alter