PRACTICAL REMARKS 115 



ordinary crop of mangel will contain about 300 Ibs. of potash, 

 and a large crop much more, it is evident that when less than 

 20 tons of dung per acre are employed, the additional manure 

 should usually be one containing potash as well as nitrogen. 

 Recent field experiments on the economical use of manures 

 have frequently shown that the use of very heavy dressings of 

 dung is not profitable, and that it is better to employ a smaller 

 quantity, and supplement it by artificial manure. Supposing 

 that 10 tons of farmyard manure are employed for the mangel 

 crop, we should probably do right to use with this, 2 cwts. of 

 superphosphate, 4 cwts. of kainite, and 3 cwts. of sulphate of 

 ammonia. This will of course be a more liberal manuring 

 than that previously mentioned. 



Recent research has pointed out that when ammonia salts, 

 or nitrate of soda, are to be applied to land which also receives 

 farmyard manure, the latter manure should be well rotted. 

 If fresh manure is used it should be applied to the land a month 

 or more before the nitrate or ammonia salt. In the case of 

 moderate dressings of farmyard manure, and in ordinary sea- 

 sons, there is little evidence that any injury is to be feared, but 

 as the danger of denitrification would increase if continued 

 wet weather followed, it is wisest to avoid any chance of loss 

 by adopting the precautions named. 



The thorough mixing of the ammonia salt and other 

 artificial manures with the soil before sowing the seed, which 

 has been the plan employed at Rothamsted, will in most cases 

 be found the best plan to adopt. 



TURNIPS 



The character of the turnip crop, and its behaviour towards 

 manures, are in several important points very different from 

 those of the crops previously noticed. The land which is to 

 bear a turnip crop receives an ampler preparation by tillage 

 than is afforded to any other crop in the rotation ; and this tillage 

 is continued by hoeing far into the summer. The process of 

 nitrification in the soil is thus pushed to its extreme limits, and 

 much of the accumulated nitrogenous organic matter in the soil 

 is converted into available plant food. Not only is the supply of 



