PT. II, CH. vi] Soil Types 95 



The distinction is well illustrated by the following 

 experiment due to S. T. Parkinson^. A trench was 

 dug 5 ft. broad, 30 ft. long and 3 ft. deep: the sides 

 and bottom were lined with loose bricks and stones, and 

 four partitions were put up. The divisions were then 

 filled respectively with a good loam, a peat, a gault 



LOAM 



.^v' 



PE/VT 



GAULT 



3ft.- 



Fig. 25. Carrots grown on various types of soil. 

 (S. T. Parkinson's experiment.) 



clay, a poor sand and broken chalk. Carrots were sown 

 and gave results shown in Fig. 25. The student should 

 repeat the experiment using typical local soils. The 

 observed differences depend on the intrinsic properties 

 of the soil, the extrinsic conditions being the same for all. 

 The chief intrinsic conditions are that the soil must 

 be capable of going into a good tilth, that it must con- 

 tain enough of all the constituents required for the plant 

 and that it must not be "sour," while the most impor- 

 tant extrinsic conditions are that it must be sufficiently 



1 Journ. Smith Eastern Agric. Coll., Wye, 1910, 258-261. 



