EXPERIMENT FARM AT SOUTHERN PINES, N C. 41 



food in various combinations. Thus one plot receives no 

 fertilizer at all ; another plot is fertilized with only potash 

 and nitrogen ; a third plot has potash and phosphoric acid, 

 while a fourth has all three elements of plant food, namely, 

 potash, phosphoric acid and nitrogen. Further variations 

 are made by increasing and decreasing the amounts of 

 potash or the other two ingredients. On some plots lime 

 is added, while green-manuring is given to other plots in 

 order to study its effects. These experimental plots usually 

 are 1/20 or i/io of an acre in size and are separated by 

 paths and roadways. Each series is cultivated, harrowed 

 and treated in the same manner, except as to the amounts 

 of fertilizer used. 



The progress of these experiments is being carefully 

 noted during the growing season under the guidance of 

 trained observers, and a careful record is kept of all obser- 

 vations made, to ascertain not only the rate of growth, but 

 also the general vigor and health of the plants upon the 

 different plots, also the effects of wet weather, drouth, 

 disease, attacks of insects, etc. At the end of each season 

 the product from each plot is compared in quality with the 

 yield from other plots, while the quantity grown in each 

 plot is accurately measured. 



The experiments with each particular crop are con- 

 tinued through a series of many years, so as to obtain an 

 average and a true knowledge of the various conditions 

 and effects, from which the irregularities of certain seasons 

 have become eliminated. It is only after a number of sue- 



