LEGUMINOUS CROPS. 



125 





1878 inclusive, and no manure since, 347.3 lb. of nitrogen Yield of 

 were gathered per acre, almost wholly by the leguminous nitr °9^- 

 crop — clover. On a plot on part of which the mineral 

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

 monium-salts or nitrate had been applied up to 1878, but 

 nothing since, 330.2 lb. 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 up to 1878, the yield of nitrogen 

 in the barley and clover was 280.9 lb. 



Here, then, in a field where beans had been grown for Large 

 many years in succession, and had yielded much less than fromsM >S 

 average crops, and the land had then been left fallow for poor in 

 several years ; where the surface-soil had become very poor mtro 9 en - 

 in total nitrogen ; where both surface and subsoil were very 

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

 minimum amount of crop-residue near the surface for decom- 

 position 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 soil 

 the surface-soils became determinably richer in nitrogen as ^^ ™ y 

 the results in Table 41 show. There are there given the the clover. 

 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 it per acre, in the 

 surface-soils, 9 inches deep, at the different dates ; also the 

 estimated gain of nitrogen under the influence of the growth 

 of the clover. 



TABLE 41. — Nitrogen, per cent, and per acre, in the surface- 

 soils, BEFORE AND AFTER THE GROWTH OF THE BARLEY AND CLOVER. 



