102 The Control of tlie Soil [ft. ii 



the district must also be cleaned regularly. If the land 

 is not wet enough to need actual pipe drains it may still 

 require a water furrow to carry away excess of rain, and, 

 should no natural outlet occur, a sump or a dell may be 

 made, as is done in parts of Hertfordshire. The great 

 point is that water must not stand about on the land. 



It is not enough that the soil should go into a good 

 tilth and be of sufficient depth : it must also contain all 

 the things wanted for the proper growth of the plant. 

 The soil, in short, must be complete, containing adequate 

 quantities of sand, silt, clay, calcium carbonate, organic 

 matter, and the various nutrient salts. Many natural 

 soils are lacking in some direction or another, but it is 

 usually possible to make good the defect. The farmer, 

 however, wants more than this: he wants to make a 

 profit on the transaction, and therefore a compromise 

 usually has to be effected between the ideal and the 

 commercial. Sand can be added if necessary, but 100 

 tons or more would commonly be required per acre to 

 make ajiy appreciable difference. This would cost too 

 much to be practicable in England although it can be 

 done in countries where labour is very cheap. Clay can 

 be added at less expense because a dressing goes further 

 than in the case of sand : the operation becomes a com- 

 mercial possibility when the clay contains calcium car- 

 bonate^, so that two desirable constituents are added in 

 one operation. Illustrations are afforded in the Isle of 

 Ely, where such clay is obtained from below the surface. 

 The method consists in laying trenches. 18 yards apart, 

 and in each digging holes ten to the chain and sufficiently 

 deep to reach the clay: about a ton is then got from 

 every hole and spread round about. The cost of the 



^ This mixture is called MarL 



