242 FARMYARD MANURE [chap. 



means, such as the ploughing-in of green crops, must be 

 employed in order to maintain the stock of humus. 

 The effect of dung upon the soil is seen in two ways. 

 In the first place, it will cause the surface soil to absorb 

 more of the rainfall and to hold it up near the surface, 

 so that cases may be found in which the subsoil is 

 actually drier where farmyard manure has been used, 

 because the rain has been held near the surface and 

 therefore within reach of evaporation. But the chief 

 value of the humus which the farmyard manure con- 

 tributes to the soil lies in the better texture that it 

 induces. It is particularly noticeable in the number of 

 plants that are obtained when growing turnips and other 

 root crops. When soils have long been farmed without 

 organic manure, however rich they may be in the con- 

 stituents of plant food, there will be great difficulties and 

 even total failures in obtaining a proper stand should 

 the weather conditions have been unsuitable soon after 

 sowing. 



In ordinary mixed farming, undoubtedly the best 

 way of utilising farmyard manure is to apply it to the 

 root crops, and especially to mangolds and potatoes. 

 Swedes require much less nitrogen than do the other 

 root crops. They also require a firm but fine tilth ; in 

 consequence, not more than lo to 12 tons of dung per 

 acre should be given for swedes, and it should be applied 

 in the autumn, in order that it may become well rotted 

 down before the spring cultivation begins. But up to 

 20 tons of dung per acre can be profitably employed for 

 mangolds and potatoes, and it can, if necessary, be 

 applied immediately before sowing. In America where 

 corn (maize) takes the place of root crops, the farmyard 

 manure may most profitably be applied to that crop. Any 

 surplus dung, after the requirements of the root crops 

 have been satisfied, is probably best given to the young 



