564 



Afjricultural Chemistry—- Turnips. 



such manures for turnips^ notwithstanding that the value of our 

 produce as food depends much upon the percentage of nitrogen 

 it contains. 



On some future occasion we shall endeavour to show that, 

 excepting rape-cake, the manures in the market containing nitro- 

 gen are more advantageously employed for clover, and other crops 

 of the like kind, than in any other place in the rotation. 



If a proper quantity of imported food be consumed upon a 

 farm, the direct supply of nitrogen to the turnip crop by means of 

 artificial manures will certainly not be necessary. An excess of 

 nitrogen in the soil produces too large a proportion of leaf, and 

 too little tendency to form bulb. It is true that a crop of turnips 

 having a large proportion of leaf will give a larger amount of 

 manure to the land ; but its yield of food will be comparatively 

 small. But, since the manure obtained in such a case previously 

 existed in the soil, the economy of the crop, even so far as its 

 manuring influence is concerned, may be doubted. In fact, so 

 far as our experiments upon this subject enable us to judge, we 

 believe that where the supply of nitrogen to the soil is very great, 

 the amount of it collected from the atmosphere is less, and thus a 

 part of the benefit of the crop would be lost. All the specimens 

 in which we found a high percentage of nitrogen were those in 

 which there was a great development of leaf with a compara- 

 tively small tendency to form bulb ; and we believe that the high 

 percentage was due to a deficient accumulation of carbon by the 

 plant. Whilst, then, a high percentage of nitrogen may indicate 

 an abundance of it in the soil, the growth of the plant has been 

 in other respects defective. It is probable that the full-grown 

 bulb of such a plant as has only a due proportion of leaf will sel- 

 dom have a percentage of nitrogen much higher than that which 

 has been usually observed ; for with an increased supply of ni- 

 trogen there is an excessive production of leaf, and a bulb which, 

 though richer in nitrogen, is not profitably developed. There is, 

 however, a casual advantage in having a somewhat full supply of 

 nitrogen in the soil for those of our turnips which are to be eaten 

 late in the season ; for the plants so grown, whilst they may have 

 a less favourable proportion of bulb, yet, owing to the increased 

 vitality and hardiness which result from the nitrogenous ma- 

 nure, the bulb is better fitted to stand the winter temperature 

 without injury. A sufficient importation of food for stock will, 

 however, render the purchase of nitrogenous manures for the 

 turnip crop quite unnecessary; but where such manures are em- 

 ployed, rape-cake will be found to afford a sufficient, and in other 

 respects the most advantageous, means of supply. 



Lastly, it must not be forgotten that the tillage of the soil con- 

 stitutes a most essential element in turnip culture ; and that he 

 who sows his turnip-seed upon a badly- cultivated soil is only 



