Experiments upon Swedes. 161 



In explanation of the results of these field trials, I beg to offer 

 the following observations : — 



1. It will be seen that only those plots yielded an increase 

 ■which contained phosphates ; the other manuring constituents 

 either had no effect upon the turnip crop, or slightly di- 

 jninished it, 



2. On comparing the produce of No. I. with that of No. XI., it 

 will be seen that 3 cwt. of superphosphate, made from bone-ash 

 and sulphuric acid, and containing no appreciable quantity of nitro- 

 gen, produced as good a result as 15 tons of well-rotten farmyard 

 manure. This is an important fact, well worth the serious con- 

 sideration of the farmer ; and though I would not be understood 

 as saying in general terms that I consider 3 cwt. of good super- 

 phosphate to be worth, for the turnip crop, as much as 15 tons 

 of well-rotten dung, I believe there are many soils in England 

 which require nothing else but 2 or 3 cwt. of good superphos- 

 phate drilled in at the time of sowing, with liquid manure drill, 

 in order to yield an abundant crop of turnips. 



3. It is worthy of notice that 6 cwt. of bone-ash superphos- 

 phate hardly produced a heavier crop than 3 cwt. ; and also that 

 12 cwt. of the same superphosphate yielded only 17 cwt. and 

 76 lbs. more than a dressing with 3 cwt. There are soils on which 

 experience has shown that a large dressing of superphosphate 

 produces a more favourable result than a more scanty supply of 

 this fertilizer. I believe this to be the case with most light and 

 sandy soils. But in the majority of instances, I have no hesitation 

 in saying that much more superphosphate is applied to the land 

 than is really required to produce the maximum effect which this 

 fertilizer is capable of producing. Tiiis remark, however, applies 

 only to superior superphosphates, rich in soluble phosphate of 

 lime, and not to the majority of superphosphates which find 

 their way into the hands of the farmer ; for I regret to say there 

 have been sold this season many samples so poor in soluble 

 phosphate, that 2 cwt. per acre can produce but little effect ; 10 

 or 12 cwt. of such superphosphates certainly will prove superior 

 in efficacy to 6 or 8 cwt. of the same. 



4. Gypsum had no effect whatever on the turnip crop, a result 

 which was to be expected upon a soil naturally containing nearly 

 I percent, of sulphate of lime. Indeed, gypsum yielded 14 cwt. 

 less turnips per acre than the average produce of the unmanured 

 plots, but I do not think it had an injurious effect, and ascribe 

 the slightly-diminished produce of plot No. II, to purely acci- 

 dental causes. 



5. It will also be seen that neither sulphate of ammonia nor 

 sulphate of potash had any effect, and that sulphate of soda pro- 

 duced but a small increase. The inefficacy of these sulphates 



VOL. XIX. M 



