112 TALKS ABOUT THE SOIL. 



We will suppose that potatoes have been used. 

 During the growing-season, carefully observe the dif- 

 ferent plats, and see if any one or more appears to 

 be more or less thrifty than the others. Notice which 

 plat appears to mature first, and which blooms first, 

 and keep a record of the observations. At the end of 

 the season, carefully dig the crop on each square, gath- 

 ering all the tubers large and small, and weigh each 

 lot. First weigh the crops on squares 2 and 9. This 

 will serve as a standard of comparison, as it will show 

 the natural condition of the soil. If there is any 

 difference between them, get the average. Record the 

 weights in each lot ; and, just for illustration, we may 

 say it is something like this : Average of 2 and 9, 

 80 Ibs. ; No. i, 380 Ibs. ; No. 3, 250 Ibs. ; No. 4, 360 

 Ibs. ; No. 5, 350 Ibs.; No. 6, 300 Ibs.; No. 7, 220 

 Ibs. ; No. 8, 400 Ibs. ; No. 10, 100 Ibs. This is a 

 purely imaginary crop. It might vary greatly in differ- 

 ent soils, and this variation is the point we want to 

 notice. On the particular soil we are supposed to be 

 testing, we clearly see that the land is benefited in 

 some degree by the addition of every element. Cal- 

 cium helps, and this means that it should be used 

 on that soil in addition to any and all of the others. 

 Potassium and phosphorus helped the most alone, 

 and still more when put together. All three elements 

 naturally produced the best results of all. It is plain 

 that this soil needs all four, calcium, nitrogen, phos- 

 phorus, and potassium. Squares Nos. 10, 3, 7, and 5 

 show us the proportions in which these elements should 



