by one half compared with plots subjected to dry spells of 7 days.Nedulation and nitrogen production in tops were similarly affected. Thus, for the species tested, the response to irrigation was much greater with the legume than with grasses. and without mulch, imder a range of w a t e r i n g frequencies a t t h e f i r s t isampling. 1533.10. Mean number of nodules recovered from s i r a t r o a t t h e f i r s t sampling, from p l o t s w i t h and without mulch, and grown under a range of watering f r e q u e n c i e s . 155
3.11u R e l a t i o n between nodule number and nodule weight a t t h e f i r s t asampling. 1^6^
. 1 2 . R e l a t i o n s h i p of weight of n i t r o g e n i n tops:; (g.)and volume of nodules; (mli) a t t h e second sampling. 157 3.13* Diagrammatic r e p r e s e n t a t i o n of mean diy m a t t e r production per day from l u c e r n e and s i r a t r o i n t h e second s e a s o n . Shallow soils exaegerate this stress con.ition which is likely to occur eveil when soil moisture supply is 600d.An important feature of a water harvesting project is that its irrieated pastures rely on runoff for their water supply, and such runoff is erratiic; -depending on such things as rainfall intensity and duration, slope of the land, surface cover, infiltration rate, antecedent soil moisture, and catchment area. Generally, however, it.could be expected that a water supply should become available in the summer storm season (December to March), and that irrigation could be carried out in autiann, winter, and spring when native pastures are at their worst for animal production.However, periods will occur when no irrigation water is available, and plants will then suffer from high water stress, and possibly desiccation. This could be common in early summer, when the storage ha,s been emptied by prior irrigation, and is awaiting replenishment. Plants without good drought resistance could not withstand these conditions, and so would not be suitable components of perennial pastures unless they had good re-seeding capabilities.Areas which may be irrigated from dajns are generally fairly small in extent, so that animals Trould not normally be grazing on the irrigated area all the jear round.Hence, it would be best to use the area to provide forage when it is most needed -i.e. autumn, winter, and spring. Management to provide a balanced pasture ma,y not be required, as it may be more convenient to allow animals to graze on the irrigated area for only conditions. An improved strain of rhodes grass was used as the compajiion species as; methods of establishing legumes in kikt^ru had not been studied, and after the experience with experiment Al it was expected that rhodes grass would invade the area. The productivity of these mixtures was measured over a period of two years, and, following a further period of two years daring which time plants were subjected to severe drought conditions, persistence of the species was ol^erved.
II REVIEW OF LITERATUREA. THE CLIMATE AT LA.WES.
