ON THE GROWTH OF LEGUMINOUS CROPS. 



29 



was not brought under experiment until 5 years later than the other 

 plots. 



Thus, on a plot where a purely mineral manure containing potash, 

 but no nitrogen, had been applied for 27 years, to 1878 inclusive, and 

 no manure since, 347 '3 Ibs. of nitrogen were gathered per acre, almost 

 wholly by the Leguminous crop Clover. On a plot on part of which the 

 mineral only, and on part the same mineral manure and ammonium- 

 salts or nitrate had been applied up to 1878, but nothing since, 330*2 

 Ibs. of nitrogen were removed in the crops. Lastly, where, to half of 

 the plot no manure whatever had been applied for nearly 40 years, but 

 to the other half ammonium-salts or nitrate had been applied up to 

 1878, the yield of nitrogen in the Barley and Clover was 280-9 Ibs. 



Here, then, in a field where Beans had been grown for many years 

 in succession, and had yielded much less than average crops, and the 

 land had then been left fallow for several years j where the surface-soil 

 had become very poor in total nitrogen ; where both surface and sub- 

 soil were very poor in ready-formed nitric acid ; and where there was a 

 minimum amount of crop residue near the surface for decomposition 

 and nitrification, there were grown very large crops of clover, containing 

 very large amounts of nitrogen. 



Not only was so much nitrogen removed in the crops, but the 

 surface-soils became determinably richer in nitrogen, as the results in 

 Table XIV. (below) show. There are there given, the percentages of 

 nitrogen in the sifted dry surface-soil of the three plots for which the 

 produce and the nitrogen in the Beans have been given. The results 

 relate to samples taken in April 1883, before the sowing of the Barley 

 and Clover, and in November 1885, after the removal of the crops. 

 The first two columns show the percentages of nitrogen, and the other 

 columns the calculated amounts of nitrogen per acre, in the surface- 

 soils, 9 inches deep, at the different dates, and the estimated gain of 

 nitrogen under the influence of the growth of the clover. 



TABLE XIV. 



Nitrogen, per cent, and per acre, in the surf ace -soils, before and after the 

 growth of the Barley and Clover. 



Without assuming that the figures represent accurately the amounts 

 of nitrogen accumulated per acre, it cannot be doubted that the 



