92 The Control of the Soil [pt. il 



picably poor. This is the general rule ; exceptions arise 

 when the subsoil contains much chalk or marl, and the 

 surface soil does not ; or when the subsoil is clay, and the 

 surface soil is too light a sand. With these exceptions 

 the subsoil is much poorer than the surface soil, and 

 therefore to make it equal the gardener must add manure 

 to it. 



To get the subsoil into the same mechanical condition 

 as the surface soil without bringing it up to the top is 

 not easy because frost does not penetrate readily. Some- 

 thing can be done, however, by adding lime, limestone, 

 chalk, or basic slag, to the subsoil at the time of trench- 

 ing. 



The roots of the plants have a wonderful facihty for 

 boring their way into the subsoil, and very stout roots 

 can often be found well below the surface depth. It is 

 not clear, however, that the loosening of the soil is par- 

 ticularly helpful to these plants, indeed a soil which is 

 simply loosened and then left soon settles back to its 

 natural condition. 



Three methods of trenching have been used : 



1. The top spit is kept on the top, and manure is 

 buried in with the subsoil. 



2. The digging is done in the same way but no 

 manure is added, the subsoil being simply loosened. 



3. The subsoil is put on the top and the surface soil 

 below. 



These three methods have given rise to much dis- 

 cussion but there are times when at least two of them 

 are sound. 



The first is practically always beneficial, though it is 

 not always a commercial success. 



Experiments at the Woburn Fruit Farm and at 



