4. References to spray irrigation in section 57 of the Water Resources Act 1991 (the effect of which section is described in the Schedule hereto) shall be construed as not including spray irrigation if carried out—
(a)within a building or other structure, whether fixed or mobile, used for the production of agricultural produce, being a building or structure which excludes from the plants growing in or under it water falling as rain;
(b)on land in the immediate vicinity of cloches, in or under which plants are growing, for the purpose of securing a supply of moisture to those plants;
(c)on containers or pots in the open in which plants intended for sale are grown in such a way as to be unable to take moisture from the soil.