454 Journal of Agriculture, Victoria. [10 Aug., 1918. 



APPLE CULTURE IN VICTORIA. 



Bij J. Farrell, Orchard Supervisor. 

 (Continued from p. 363.) 



The Dam System of Irrigation. 



It has been previously stated that, although good results attend the 

 channel system in the north, relatively better returns in apple produc- 

 tion would follow the more general adoption of the dam system of 

 irrigation than accrue from the rather limited application of water by 

 this means at present obtaining in the southern fruit areas. This 

 calculation is based on the fact that apple trees, when cultivated in the 

 cooler undulating fruit districts occupying the central and southern por- 

 tions of the State, thrive better land yield heavier crops of higher quality 

 fruit than those grown on the flat lands of the warmer northern districts. 



Orchardists in districts unsuitable for channel schemes, who realize 

 the advantages to b© derived from watering their trees, especially during 

 seasons of light summer rainfall, now resort to the dam system of irriga- 

 tion. The conditions militating against channel systems arise from the 

 serious irregular undulations in the physical features of those districts, 

 the absence of natural permanent streams and the consequent lack of 

 regular supply. Fortunately, however, the usually copious winter rains 

 experienced in such places are ample, when systematically accumulated 

 and carefully stored, to supply the normal irrigation requirements of 

 local orchardists during summer. 



Dam and Reservoir Construction, Water Accumulation and 



Storage . 



In selecting the site for a dam from which to irrigate by gravita- 

 tion, care should be taken that it be placed at a level high enough to 

 command the whole of the area to be watered. The ground chosen for 

 the excavation and to form the embankment should be of a retentive 

 character so as to prevent the escape of any of the accumulated water 

 by seepage. Mistakes are often made through constructing dams in 

 porous clays. Not alone is the orchardist thus deprived of the use of 

 the water during summer, but the trees below the dam suffer from the 

 seepage. 



Provided the soil on any part of a main slope will hold water, the 

 ground contour of the surroundings should be fully considered before 

 the position for the dam is decided upon. An area on which small 

 depressions of suitable lateral decline converge should be chosen. By 

 this means an adequately extensive water-shed may be provided and 

 ample catchment insured. When the plane of a slope is of even grade 

 the exca s'^atioLi may be made in a convenient position, then a few small 

 open drains or plough furrows running diagonally across the slope to the 

 dam will carry in the water. 



When the site has been fixed upon, the building of the dam should 

 be commenced by removing the whole of the surface soil from the dam 

 area, including the portion forming the base of the embankment. This 

 soil, being friable and consequently unsuitable for use in constructing 

 the base of the embankment particularly, may be utilized in filling up 

 minor depressions in the orchard surface to bring it to a more even 



