EXPERIMENTS CONDUCTED WITH A VIEW TO CONTROLLING DISEASE. 43 



Whatever improves the physical or mechanical condition of the soil would seem, therefore, 

 to aid in reducing the amount of Pit. The absorption and retention of moisture largely depends 

 upon the texture of the soil, and suitable tillage increases its capacity, as well as the addition of humus, 

 if necessary, in' the form of green manuring. To maintain a regular supply of moisture, especially 

 at the fruit-growing season, is one of the great requirements for the production of healthy fruit, and 

 to keep this water moving in the soil, so as to carry with it the plant food in solution and to draw the 

 atmospheric air after it, is promoted by drainage. 



As regards the chemical constituents, the magnesia is in much larger proportion in the 

 "Gracefield" soil, and in excess of the lime content; but what effect this may have on the fruit grown 

 upon it we do not know. A considerable amount is known to exist in chlorophyll, and it is probably a 

 constituent of the living substance itself. There are soils, however, such as those at Bacchus Marsh 

 (see Irrigation Experiments), which contain a superabundance of magnesia, and yet the apples pro- 

 duced there are of high quality and not particularly liable to Bitter Pit. It is generally considered 

 advantageous to have an ample proportion of lime in such soils, and Hilgard, in his work on "Soils," 

 sums up our present knowledge : "In general it is best that lime should exceed magnesia in amount." 



MAY BROS.' ORCHARD, SANDFORD, TASMANIA. 



In this orchard, where Cleopatras are grown every year in considerable quantities, even to 

 the extent of thousands of cases, there has never been any serious loss from Bitter Pit. 



The age of the trees varies from about ten to over thirty years. The system of pruning adopted 

 is rather light. The orchardists state that "it would probably be considered rather on the light side, 

 as we leave more branches on the tree than is usually the case." The nearest part of the orchard to 

 the beach is just about eighty yards from high-water mark, and it is protected by sandhills, which are 

 overgrown by a natural shelter of trees and bushes. The soil is a very light sand, not unlike that 

 upon the beach, and most of it has a clay subsoil, which is frequently from eight to ten feet below 

 the surface. 



Although the season was the driest on record, the rainfall being under thirteen inches, there 

 has seldom been a finer crop of Cleopatras, either for size or quality, with scarcely a trace of Pit. 



The Cleopatra is well known to be superior to Yates in the quality of drought resistance, 

 and the former thrives best in a rather dry climate and on a very light soil. 



That soil and climate exercise an important influence on the development of the disease in 

 varieties subject to Pit is evident from the above, which is given as a typical example. 



XIV. EXPERIMENTS CONDUCTED UNDER NATURAL CONDITIONS 

 WITH A VIEW TO CONTROLLING THE DISEASE. 



A. MANURIAL EXPERIMENTS. 



The main object of these experiments has been to determine the influences of the various 

 fertilizers upon the development of Pit, and incidentally the yield in relation thereto. They have been 

 conducted in each of the States, with the exception of Tasmania, under the most varying conditions 

 of soil and climate. At the end of four years the manures have begun to produce their special effects 

 and to give indications of the direction in which they act. All the various results have now to be com- 

 pared and co-ordinated in order to see chiefly what fertilizers increase or diminish the Pit. 



No attempt will be made to enter into detail as to the effect of the individual manures, but to 

 give the essential points as a basis for comparison throughout. The fertilizers yielding the greatest 

 and least amount of Pit in each State will be singled out and contrasted with the highest and lowest 

 yields. In this way some general conclusions may be arrived at, as to the relation between Pit, yield, 

 and fertilizers. 



