756 ANNUAL REPORT OF THE Off. Doc. 



problem is rarely presented to the horticulturist. Most persons 

 are asking how to improve, by fertilization, a soil that they know is 

 not sufficiently rich in plant food. The belief is quite current among 

 farmers that the chemist can analyze the soil and tell them what it 

 neds. Unfortunately, this is not true. The chemist can ascertain 

 the total amount of nitrogen, phosphoric acid and potash a soil con- 

 tains, but he cannot tell how much of that is in such a form as to be 

 available to the plant. 



Still a third method has been advocated, called the plot system. 

 The principle of the test is simple and the details are not difficult 

 to carry out. The plot is divided into several long narrow strips of 

 equal size. Some receive no fertilization, some nitrogen alone, some 

 phosphoric acid alone, some potash alone, others mixtures of two of 

 these and some all three; that is a complete fertilizer. The field is 

 all sown in the same crop and at harvest each plot is harvested and 

 weighed separately. The applications that have given the largest 

 yields show what the soil needs most. The objections to this are 

 twofold. In the first place, results obtained with one crop have but 

 a limited application to a crop of another nature. In the second 

 place, the results show what the land needed at the beginning of the 

 season, and not what it is going to need for the next crop. In other 

 words, the results tell you what you want to know, one year after 

 it will do you any good. 



To my mind both these latter theories are based on an entirely 

 wrong idea of the proper use of the plant food already in the soil. 

 In both, the idea is to add to the soil as little new plant food as pos- 

 sible, and to make the fullest possible use of the plant food already 

 in the soil. 



My own belief is that the proper theory of fertilization should be 

 based on the idea that all of the plant food of the soil should be con- 

 sidered as so much working capital and enough added so that this 

 working capital shall be continually increased. In other words, I be- 

 lieve that the only proper method of fertilization is to fill the soil 

 so full of plant food lliat there is no possibility of the plant lacking 

 in nourishment. 



In this same line I might say just a word about the use of lime. 

 Most persons use lime in order to make available the otherwise un- 

 available plant food of the soil, consequently, any crop grown by the 

 use of lime alone leaves the soil just so much the poorer in plant 

 food and is, therefore, directly opposite to what I have just stated as 

 what I believe should be the proper idea of crop fertilization. The 

 fact is that any and all crops need at. their command a great deal 

 more of plant food than they are to remove from the soil. 



Some common crops remove the following amounts of plant food 

 in pounds per acre: 



