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Agricultural Chemistry — Turnips. 



A practical farmer, accustomed to consume his turnips upon his 

 land every fourth or fifth year, might be inclined to doubt the 

 correctness of any conclusions drawn from a set of experiments so 

 artificial as the removal of five successive crops of turnips from 

 the same field. It should therefore be distinctly understood that 

 the object of these experiments is not to provide any examples for 

 direct imitation in practice, but to enable us to ascertain the real 

 characters of season, soil, and manuring required for the growth 

 of the turnip, in order that, the principles of its culture being 

 better understood, the practice of it may be more economically 

 carried out. In our experiments upon wheat, given in the last 

 number of this Journal, we showed that the produce of grain, 

 beyond that which the soil and season gave in successive years, 

 was dependent upon the supply of nitrogen; that 100 lbs. of rape- 

 cake, containing 5 lbs. of nitrogen and 80 to 90 lbs. of carbonaceous 

 matter, gave no greater increase of corn than a salt of ammonia 

 containing 5 lbs. of nitrogen and no carbonaceous matter ; and 

 that the produce from 14 tons of farm-yard dung upon the same 

 space of ground year after year, was invariably less than that 

 which was obtained from 2 cwts. of ammoniacal salts. The farm- 

 yard dung and rape-cake increased the produce of grain in pro- 

 portion to the amount of nitrogen which they contained ; but as 

 the rape- cake contains only 5 per cent, of nitrogen^ and dung 

 frequently not a i per cent., or one pound in 200, to what pur- 

 pose can this bulk of carbonaceous matter be applied ? As long 

 as corn is cultivated, it is evidently of little use. Our experiments 

 upon turnips answer this question in a most satisfactory manner. 

 They show distinctly that the production of turnip-bulb depends 

 upon the supply of carbonaceous matter in the soil, and that the 

 true office of the turnip and other root-crops consists in converting 

 the otherwise useless refuse of our corn-crops (straw) into a suc- 

 culent and nourishing food for animals. Durmg the five years 

 over which our turnip experiments have been carried; in only one 

 instance has the acreage weight of bulbs reached 17 tons. We 

 know that the mineral matter required by the turnip has not been 

 deficient, and in many instances very large quantities of nitrogen 

 have been supplied ; but the essential substance, carbonaceous 

 matter, required for bulb-formation, has been but moderately 

 supplied in the form of rape-cake ; in one instance, where it was 

 supplied in a larger quantity by dung, the greatest produce was 

 obtained. Having, therefore, shown that to obtain heavy crops of 

 bulbs, large amounts of carbonaceous matters should be supplied 

 to the soil, and that dung is the cheapest source of this substance, 

 the question next arises, What are the best substitutes for it ? 

 Dung is an article in which our farm-yards are very apt to be de- 

 ficient. It might be supposed that if sufficient carbonaceous 



