and Magazine of the Ceylon Agricultural Society. 291 



Why not go back to 1902 when tho yield, as 

 far as I can discover, was 182 lb. per acre ? How 

 did it become 420 lb. in 1903, without manure, 

 or prunings, or albizzias? The increases for the 

 years given are 14'5, 4'7, 29, and 8'2 per cent. It 

 would be interesting to know the reason of these 

 periodic differences in the annual increase: is 

 it pure chance that the greater coincide with 

 the two great increases in the total Ceylon crop 

 since 1904? It may be pointed out, by the way, 

 that a difference of 8 per cent, in a held experi- 

 ment is regarded as inconciusive. Some fields 

 yielded 700 lb. per acre in 1904 : have they 

 shared in the general increase, and do they 

 now yield 1,150 lb. per acre? How is it that 

 Mahawale shows in one year a gain of 14 per 

 cent., when "from the burying of prunings, 

 quick returns are not to be looked for, or ex- 

 pected," and another estate, more liberally 

 treated, does not show a profit for four years ? 



But when was Mahawale opened ? I do not 

 find it in the Directory for 1896-7. And were the 

 650 acres of tea all planted at the same time ? 

 Apart from the fact that it is not an experiment 

 in burying tea prunings, it would appear that 

 all the cards are not on the table in this case. 



Take now the ".definite experiment" on two 

 adjoining fields. The average crop for the two 

 H was under 300 lb. per acre. It is unfortunate 

 that the yields are not given separately, because 

 if one gave 330 lb. and the other 270 lb. , the bot- 

 tom is knocked clean out of the experiment. But 

 this does not affect the value of the experiment 

 from the point of view of the present discussion. 

 "A" had cultivation, buried prunings, basic slag, 

 sulphate of potash, and artificial manure. B had 

 artificial manure only ; and the two fields were 

 not treated at the same time, This last may be a 

 minor detail : Still, it is best to avoid all pos- 

 sible errors in making a " definite experiment." 

 After eight years' treatment, A shows an ad- 

 vantage of 33 per cent, per annum over B. It 

 is no doubt a successful experiment in manuring 

 tea ; but if it was designed to show the benefit 

 derived from burying prunings, it was most 

 hopelessly misconceived. It only shows that the 

 treatment accorded lo A gives a better yield than 

 the treatment accorded to B. But do the culti- 

 vation, and the basic slag, and the sulphate of 

 potash count for nothing ? How much of the 

 gain is due to each ? To make a difference in four 

 factors (or five, if the time is taken into account), 

 and then to quote the result as a proof of the ad- 

 vantage of one of them, is utterly unjustifiable, 

 and it supports tho previous contention that 

 what passes for experiment in tropical agri- 

 culture is often the most feeble imitation. Ex- 

 amples of such "experiments" can be quoted 

 by the dozen, and none of them proves any- 

 thing " definite." To obtain any evidence on the 

 subject of burying prunings, B should have re- 

 ceived exactly the same treatment as A, 'minus 

 the prunings, at the same time, even to the ex- 

 tent of digging holes and filling them up again, 

 and there should have been a control plot. 



I have been referred to theories and figures 

 Bent some years ago to the Experiment Station 

 Committee. The figures there are nearly those 

 published in Saturday's issuo, viz., that the 

 prunings from a highly-manured, well-plucked, 



medium-pruned estate, with large well dove- 

 loped bushes, remove 101 lb. of nitrogen per 

 annum, etc. Presumably this is 202 lb. per 

 pruning. The figures are indisputable. I do not 

 mean that they are correct, but that they are 

 not open to discussion. We might just as well 

 be told the total of an obliterated column of 

 figures, and asked to discuss its accuracy. If 

 the justification of the burial of prunings 

 is to be based on their manurial value, the 

 figures must be supported by details which give 

 them some semblance of probability. 



Some idea of the accuracy of the figures 

 cited above may be gathered from the fol- 

 lowing sentence, which is quoted from the 

 manuscript referred to : "It does not appear 

 financially sound to throw or waste tea pru- 

 ning containing 4 to 4-J per cent, of nitrogen 

 in their dry substance, to be replaced by orga- 

 nic matter containing 2§| to 4 per cent, at most, 

 even though secured from the nitrogen of the 

 air by the aid of nodule bacteria." It certainly 

 does not : but whoever claims that tea prunings 

 contain 4 per cent, of nitrogen in their dry 

 substance? We are told that the leaves (dry) 

 contain 4£ per cent. Surely it is obvious that 

 the great mass of the prunings consists of wood 

 which has only a small nitrogen content. In 

 the absence of details we are left to guess 

 where the fallacies lie; but the two most pro- 

 bable are: (1) the nitrogen content of the leaves 

 is applied to the whole of the prunings, and (2) 

 there is a confusion of "wet weight" with "dry 

 weight." Percentages, to be of any use, must 

 be calculated on the dry weight, i.e., after 

 drying at 100° Cent, until constant. 



The figures for Hevca give a typical example. 

 The leaves (dry) contain 3"44 per cent, of nitro- 

 gen ; the twigs, *62 per cent. ; and the wood, - 59 

 per cent. What are the corresponding figures 

 for tea?— and will the nitrogen content of the 

 whole of the prunings exceed 1*5 per cent? To 

 estimate this we must know the dry weights of 

 the leaves and green twigs, red wood, and old 

 wood removed per acre, and the nitrogen con- 

 tent of each. As far as regards loss of weight, 

 on drying, old tea leaves lose over 60 per cent., 

 green shoots with full-grown leaves lose over 70 

 per cent., redwood loses 60 per cent, and old 

 loses over 50 per cent. 



202 lb. of nitrogen are said to be removed in 

 the prunings of one acre. If we take the nitro- 

 gen percentage as 4, this requires 5,050 lb. of 

 dry prunings; and putting the average loss of 

 weight in drying at 60 per cent. , this means 12,500 

 lb. of prunings in their natural condition. But 

 ttiis percentage of nitrogen is most probably 

 three times too great, and, therefore, the pru- 

 nings required will be about 37,500 lb per acre. 

 To illustrate our lack of facts, -can any planter 

 say, to half-a-ton, what weight of prunings is 

 removed per acre on his estate ? 



I hope the above will give some idea of the 

 figures and experiments required to solve this 

 question. At present those who advocate the 

 burial of prunings because of their manurial 

 value, give no valid basis whatever for their 

 belief. We do not know how much nitrogen 

 or what weight of dry material is removed 



