JO HOW TO EXPERIMENT. 



The only reliable way to determine the crop-making 

 value or power of a soil is by making what are called plot 

 experiments. Small portions of land, usually one-tenth or 

 one-twentieth of an acre each, are laid out on an even, 

 level field. These plots are all broken, seeded and tilled 

 precisely in the same manner, but are treated differently 

 as to applications of plant food. Some of the plots receive 

 no fertilizer, others one or two or all three of the plant 

 food ingredients and in varying proportions. The crops 

 are harvested separately from each plot, carefully weighed, 

 and their quality noted. Thus, the results obtained from 

 the various plots show the effectiveness of the different 

 fertilizer combinations in producing yield and quality. 

 Plot experiments have been made extensively for years 

 and a great deal of valuable information has been obtained 

 from them, but it is necessary to continue them more or 

 less all the time, as soils change quickly when not system- 

 atically fertilized. 



The agricultural experiment stations, as a rule, make 

 fertilizer experiments, some of them extensively, but the 

 stations have many problems in agriculture to work out, 

 and cannot give all their attention to one line of work. In 

 Europe there are a number of special experiment farms, 

 confined largely to the study of plant food and soils. In 

 this country thus far we have but one, the Experiment 

 Farm of the North Carolina State Horticultural Society, at 

 Southern Pines, North Carolina, of which a more detailed 

 account will be given later in this book. 



