CHAPTER IX 



EXPERIMENTS UPON GRASS LAND MOWN FOR HAY EVERY YEAR 



I. The Unmanured Plots. 



II. Use of Nitrogenous Manures alone. 



III. Mineral Manures used alone. 



IV. Complete Manures Nitrogen and Minerals. 

 V. The Action of Organic Matter. 



VI. Effects of Lime. 



VII. Changes in Herbage following Changes in Manuring. 

 VIII. The Effect of Season. 



Practical Conclusions and References. 



THE experiments upon grass at Rothamsted began in 1856, 

 about 7 acres of the park close to the house being set aside for 

 the purpose. The land has been in grass as long as any 

 recorded history of it exists, for some centuries at least. It is 

 not known that seed has ever been sown, and at the beginning 

 of the experiments the herbage on all the plots was apparently 

 uniform. The soil is the same stiff reddish loam as is found in 

 the other fields, though owing to the length of time the land 

 has been in grass stones are not abundant near the surface. 



The plots, of which there are twenty in all, vary somewhat 

 in size between one-half and one-eighth of an acre. Up to 

 1874 inclusive the grass was only cut once, the aftermath 

 being fed off by sheep. Since that time there has been no 

 grazing, and the plots are generally cut twice in the year. The 

 grass is made into hay in the usual way and the whole produce 

 of each plot is then weighed. On some occasions, however, 

 with the second crop, continuous wet weather has rendered 

 it necessary to weigh the produce in a wet condition and 



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