AMELIORATION OF SOIL 133 



level soil had been badly disturbed by the wind. The shelter 

 afforded by low-growing crops was considerable ; and he 

 makes the very practical suggestion that such land should be 

 always cultivated in strips, fifteen or twenty rods wide, grass 

 or clover alternating with the arable culture. 



Both the tenacity and the water-holding power of coarse 

 sandy soils may be greatly improved by a small admixture 

 with clay ; this plan admits of being carried out with 

 economical success when the clay is found in the subsoil 

 of the field, or in the immediate neighbourhood. The applica- 

 tion of marl (a calcareous clay) to light soils is a common 

 practice in the eastern counties of England; from forty to 

 sixty tons per acre are usually applied. The effect of this 

 dressing is seen for many years. 



Peaty and fen land are also much benefited by the addition 

 of clay, which increases the weight and coherence of the 

 surface soil. On Rimpau's system for reclaiming peat land, 

 trenches are cut at intervals across the peat down to the 

 clay bottom which always underlies it ; the clay is then 

 brought up and spread on the surrounding peat, the land 

 being thus drained and clayed at the same time. A similar 

 plan is made use of in the Lincolnshire fens ; the trenches 

 are in this case eight to ten yards apart. 



Another very practical mode of improving the coherence 

 and water-holding power of sandy soils is by increasing the 

 proportion of humus. For garden purposes, or on a small 

 scale, this may be done by digging or ploughing in heavy 

 dressings of well-rotted farmyard manure. On a large scale, 

 the same result may be accomplished by the ploughing in of 

 green crops, which on their decay add greatly to the store 

 of humus in the soil. Preference is usually given to legumi- 



