THE SOIL IN RELATION TO PLANT GROWTH 313 



factors that determine the water supply to the crop. The 

 water supply is usually satisfactory when the surface soil 

 contains sufficient clay and not too much coarse sand and 

 gravel, and rests on a deep subsoil containing rather more of 

 the finer particles. It is a further advantage if other land lies 

 higher and furnishes a supply of underground water. In such 

 cases the land is nearly always cultivated ; it yields early crops 

 of high quality rather than heavy crops, the tendency to 

 drought inducing early maturation, while the absence of 

 stickiness makes sowing an easy matter at any time. Fruiti 

 nursery stocks, potatoes, and market-garden produce are often 

 raised, and high quality barley is also grown. The winter 

 feeding of sheep on the land is a common way of fertilising, 

 but crops must be sown early, or the fertilising material is 

 washed out unused, and the young roots have no time to 

 strike into the subsoil before the surface layer dries out. High 

 farming is the only profitable way of dealing with these soils ; 

 any carelessness in cultivation lets in hosts of weeds, such as 

 poppies, knot-weed {Polygonum aviculare), spurrey {Spergula 

 arvensis), sorrel, horsetail, convolvulus, creeping buttercup, and 

 others. Crops should follow each other in rapid succession, 

 any interval being a period of loss ; under good management 

 two or even three market-garden crops can be secured in the 

 year, while in purely farming districts catch crops should 

 always be taken. Organic manures are very necessary to 

 increase the water-holding capacity : sheep-folding or green- 

 manuring are, therefore, very desirable. Frequent repetition 

 is necessary, as the organic matter speedily disappears. 

 Calcium carbonate is often needed and is better applied as 

 ground chalk or limestone than as lime. Potassium salts are 

 beneficial and may be added as kainit ; nitrates often give 

 remarkable results, but phosphates are not usually needed 

 because the soil conditions already tend to promote good root 

 development. Only small quantities of manure must be added 

 at the time, as the soil has little retentive power. Above all, 

 no very costly scheme of manuring should be recommended till 

 preliminary trials have shown its profitableness. 



