8 EXPERIMENT STATION RECORD. 



into the subsoil. The natural fertility of the soil may also be exhausted 

 by irrigation. 



There is ueed of experiments to show the fertilizers best adapted to 

 dry soils and to moist or irrigated soils. 



The experiments of Lawes and Gilbert, reported by Deherain/ illus- 

 trate this point. An average of 1.03 meters of water falls at Rotham- 

 sted during April, May, and June,- but in 1870 the rainfall for that 

 time was only 70 cm. The harvest of hay was very light on the soils 

 without fertilizers and also on those which received phosphates and 

 salts of ammonia. There was a smaller delicit on the plats that had 

 received nitrate of soda, as the following table shows: 



Effect of fertilizers on yieUln in dry and norrnul seasons. 



Fertilizer used. 



No fertilizfT 



Mineral fertilizer, no nitrate 



Mineral fertilizer and nitrate of soda 



Yield of hay per 

 hectare. 



1870 (dry! Average,' 

 year) . l-t years. 



Eg. 



725 

 3,625 

 7,000 



Eg. 

 2,771 

 6,527 

 7,250 



Deticit. 



Eg. 

 2,046 

 2,902 

 250 



From this it appears that the deficit was almost nothing for the soils 

 receiving nitrate of soda. Under its influence the plants are enabled 

 to send down roots to take some of the water from the subsoil, which 

 is usually moist even in years of extreme drought. France expe- 

 rienced in 1892 and 1893 two seasons of i)rolonged drought, and all 

 experiments showed that the subsoil always retained considerable 

 water at a depth which was readily accessible to deep-rooted plants, 

 such as wheat.^ 



At Rothamsted in 1870, on the meadows which we have just men- 

 tioned, the following data relating to moisture in unfertilized soil were 

 obtained: At depth of 22 cm., 10.8 per cent; 44 cm., 13.3 per cent; 66 

 cm. 19.2 per cent; 88 cm,, 22.7 per cent; 110 cm., 24.2 per cent. 



This indicates that in the case of drought plants will not perish if 

 they are able to develop roots which descend to a sufficient depth. 

 They are not likely to suffer even on a plat without fertilizers if their 

 roots descend to a depth of 66 cm. In soils rich in nitrates plants have 

 roots 1.3 meters long, and through these they take up large quantities 

 of water from the subsoil, which may contain 25 per cent moisture at 

 this depth. For this reason, as well as because they are washed out of 

 the soil in a wet season, nitrates are most effective during rather dry 

 seasons. 



1 Chimie Agricole, p. 665. 



"Lawes and Gilbert, Aun. Agrou., 1 (1875), pp. 251,551. 



3 Compt. Rend., 1892 and 1893, May to September. 



