Agricultural Chemistrij — Turnips. 497 



do not fully appreciate the nature of the question at issue ; but 

 those who choose to go through the details which we are about to 

 quote will, it is thought, find that a true understanding of them 

 tends much to explain the principles upon which the best agricul- 

 ture is founded. 



Before entering upon a consideration of the turnip results them- 

 selves, we shall remind the reader of some of the leading facts 

 which may be assumed, regarding the conditions of growth of the 

 wheat plant. 



In the paper on " Agricultural Chemistry " in the last number 

 of this Journal, a series of experiments was quoted for the purpose 

 of showing the effect of season and manuring upon the growth of 

 wheat; and a careful consideration of them led to some very 

 important conclusions regarding the nature of the exhaustion by 

 corn-cropping, and also as to the varying nutritive and marketable 

 value of specimens of grain, having different characters and com- 

 position, traceable to known conditions of growth. 



It was seen that the varying quantity and the quality of the 

 produce of a plot of land, unmanured during several successive 

 seasons, were materially dependent on the number of rainy days, 

 the inches of rain and the temperature, of the months of May, 

 June, July, and August, during which periods the accumulative 

 and elaborative processes of the wheat plant are most actively de- 

 termined. The average annual produce of the soil and season, 

 unaided by manure, amounted to about three-fourths of the 

 estimated yield of the neighbourhood under ordinary cultivation — 

 to two-thirds of that of a plot manured by farm-yard dung — and 

 to fully half as much as might be expected from as high a course 

 of farming as the soil and the climate with which we have to deal 

 would justify us in adopting. It is remarkable too that, whilst 

 the quality of this natural produce, as indicated by the relation of 

 corn to straw, and the weight per bushel of the corn, varied year 

 by year according to season, yet the characters of the crops grown 

 by very various and, in some cases, rather high manures, were for 

 each season somewhat similar to those of the produce of the 

 unmanured plot. It is evident then, that the conditions favourable 

 to an increased growth of wheat are perfectly consistent in kind 

 with the natural tendencies of the plant, and that they only differ 

 quantitativelt/ from the natural resources of soil and season, and 

 less indeed in this respect than might have been supposed. 



The following table exhibits the influence of season upon the 

 produce of turnip-bulb unaided by the supply of manure. Tlie 

 soil upon which the experiments were conducted was a somewhat 

 heavy loam, not well suited for turnips ; the previous crops since 

 manure having been wheat, clover, wheat : — 



