EXPERIMENT STATION BULLETINS. 



283 



enough to remember that while a clover crop does exhaust to some extent 

 the mineral constituents of the soil, still as a net result of the production 

 of a crop of clover hay, a field is actually enriched in nitrogen. 



This fact was clearly shown by an experiment performed at the station 

 in the summer of 1897. A sandy knoll was bearing a heavy crop of 

 clover. A section of earth four feet long by two feet wide in the clover 

 plot was dug about and left standing, the earth on all four sides being 

 removed to a depth of four feet. By means of iron rods thrust through 

 the mass of earth from a strong board at each end and cross rods extend- 

 ing from side to side, the clover roots were held in place while the sand 

 was washed away. Many of the finer roots were washed away with 

 the sand. After removing the mass of tops and roots from the place 

 in which they grew, it was photographed and separated into two parts 

 by cutting the clover an inch above the crown, thus removing with the 

 tops more than would be removed in the crop of hay. The experiment 

 was performed July 2nd, while the clover was in full bloom. 



The green tops weighed 2.44 lbs., and the roots 2.14 lbs. The dry 

 matter in the tops weighed .99 lbs. and in the roots .656 lbs. A chemical 

 analysis of the tops and roots showed the following composition of the 

 drv matter: 



Com position of clover forage and roots. 



Reducing these figures to the amounts of these fertilizing elements in 

 the tops and roots on an acre, the results can be better appreciated. 



Fertilizing constituents in tlie tops and roots of an acre of clover in full bloom. 



Nitrogen 



Potash 



Phosphoric acicL. 



Roots. 



lba. 



62.07 

 46.51 

 31.90 



In Bulletin 9, of the Mass. (Hatch) Experiment Station, analyses of 

 six samples of barn yard manure are reported. Using the average of 

 these analyses as fairly representing the composition of average barn 

 yard manure, it is possible to estimate how many tons of manure it would 

 take to supply to the soil the amount of nitrogen left in it by the roots 

 of a heavy crop of clover. According to the figures obtained from the 

 bulletin referred to, barn yard manure contains .289 per cent of phos- 

 phoric acid, .582 per cent of potash and .441 per cent of nitrogen. To 

 supply the amounts of these elements left in the soil in the roots of the 



