PRECAUTIONS NECESSARY IN MAKING EXPERIMENTS 

 WITH FERTILIZERS. 



In the preceding pages it was shown how to make 

 experiments with fertilizers on a simple and also on a 

 more elaborate scale. The proposition is to judge the 

 effect of fertilizers from the actual increase produced by 

 their use. This is simple, indeed, yet accurate manipula- 

 tion and many precautions are necessary to make such 

 experiments really truthful and reliable, and as a guide to 

 the practical experimenter, the following rules are given : 



1. The greatest care should be taken to select a 

 portion of the field which is as even in fertility as possible. 

 Lack of uniformity of soil will give misleading results, and 

 often render the experiments of little value. 



2. It is best to select level land for experimenting. 

 If. such cannot be had, make the experimental plots run up 

 and down the slope, so that the washings by rain will not 

 carry the fertilizers from one plot to another. 



3. Land that has been freshly cleared, that has been 

 fertilized in preceding years, or that has been in sod, is not 

 well adapted for experiments, because such locations are 

 often uneven in fertility, and, therefore, would not give 

 reliable results. 



4. The experimental field can be measured by a 

 chain or pole, marked with feet and inches. Each plot 

 should be indicated by stakes or stones at the boundaries,, 

 so that the divisions will be well defined. It is best to 



