Feb. 1907.] 



75 



Edible Products. 



EFFECT OF TREATMENT ON SOIL. 



The third necessary point to determine a complete investigation of the effect 

 of any treatment is its influence on the soil. As a rule its estimation can only be 

 made by continuing the experiment over a long series of years. Our methods of soil 

 analysis are far too clumsy to be of any value in discovering the slight changes pro- 

 duced by any application in one year. The means to hand with annual crops of 

 determining the point by growing a second crop and making the latter the test of 

 any chauge in the soil is not possible in our case ; and hence it is only feasible to get 

 at the result by continuing the experiment for a long time. 



EFFECT OF TREATMENT ON THE BUSH. 



The same long continuance of the experiments is required for ascertaining 

 the effect of a treatment on the bush itself. But, in this case, the progress can be 

 measured annually, to a certain extent, with more ease, All old tea is uneven — this 

 is a necessity of the case. If we classify the bushes at the begining of a treatment 

 and go over the same ground at the end of each season, the change in the proportion of 

 good, medium, and poor bushes will give us a measure of what the treatment is doing. 

 In all comparative tests on old tea, the same classification is necessary for another 

 reason. However even a piece of tea looks to the eye, when it is divided into sec- 

 tions, it will be found that these are not equal. Hence when old tea is made use of, 

 before any comparative work can be done, we must know the relative value of the 

 bushes in each plot, and correct the figures of leaf weights accordingly. In laying out 

 the Heeleaka experiments, where very old tea had to be dealt with, the bushes were 

 divided into ten classes varying from worthless ones for yield (Class 0) to the best of 

 all (Class 9.) Every bush, on all these areas utilised, was hence mapped, and by 

 adding together the values assigned to each bush the original relative value of each 

 plot is ascertained. This will be repeated at the end of each season and so a measure 

 of the change in the permanent condition of the bushes by the treatment will be 

 obtained. We have now indicated the points to be ascertained in a series of experi- 

 ments, and the general methods which are being adopted to get at them. We must 

 now specify in more or less general terms what are the problems which await solu- 

 tion, and which are being or will be tackled at the Heeleaka station, 



MANURIAL EXPERIMENTS. 



First and foremost, undoubtedly, stands the question of the effect on yield 

 and quality of the bushes, of materials added to the soil as manures. It is generally 

 recognised, that the principal chemical ingredients of plants which must be supplied 

 from outside in exhausted soils are (1) nitrogen with which organic matter is closely 

 associated, (2) phosphoric acid in some form or other, (3) potash, and (4) lime. But, 

 hitherto, little definite information has been at hand of the results of the application 

 of any of these in the case of tea. The last constituent mentioned above, lime, is 

 extremely deficient in almost all tea soils, and hence nearly all English analysts, 

 consulted about the manurial experiments of tea soils, have specified lime in 

 large quantity as an essential ingredient in whatever fertiliser was added. 

 Whether these opinions are correct is extremely doubtful, as, according to our 

 experience, the tea plant is damaged by more than a very small quantity of this 

 constituent. The matter needs setting at rest, -and in our manurial experiments 

 there have been arrangements made to compare the effect of adding (1) lime alone 

 (2) lime with organic manures like oilcake, with (3) a plot to which no manure is 

 added. 



We may for the present, take the next two constituents specified above 

 together-phosphoric acid and potash. These seem to have a close connection with 

 the quality of the leaf, and their addition forms, hence, a most important part oi 



