SPRING AND AUTJJMN DRESSINGS 



51 



the soil, and wash out very readily if heavy rain falls during 

 the early winter. This is seen in the analyses of the drainage 

 water collected beneath Plot 15. It is generally very rich in 

 nitrates in the autumn as compared with Plot 7 ; whereas in the 

 spring, when the ammonium-salts are applied, a corresponding 

 loss does not happen with Plot 7, because the crop then 

 occupies the land and is able to take up the nitrates as fast as 

 they are formed. 



The diagram Fig. 7 shows the estimated loss of nitrates in 

 Ib. per acre on these two plots during the summer and winter 

 respectively, between the spring sowing of manures in 1879 and 

 the corresponding date in 1881. 



Table XVIII. shows that the drop in yield due to the autumn 

 application is very small in dry winters but becomes considerably 

 more serious in wet winters. 



TABLE XVIII. Comparison of Spring and Autumn Dressings of 

 Ammonium-salts in Wet and Dry Seasons respectively. 



* The years of low winter rainfall were 1889, 1890, 1891, 1893, 1898, 1901, 1902, 1903, 1905, 1906, 1909. 

 t The years of high winter rainfall were 1892, 1894, 1895, 1896, 1897, 1899, 1900, 1907, 1908, 1910, 1911. 



Plots 17 and 18 further illustrate the fate of ammonium- 

 salts. These plots receive the dressing of Plot 7 400 Ib. 

 ammonium-salts and complete minerals but the ammonium- 

 salts and the minerals are applied in alternate years to the two 



