58 AGRICULTURE OF MAINE. 



potash, and the chief shortages occur in nitrogen and phos- 

 phates, although the latter materials are actually required in 

 considerably smaller amounts. 



From these facts it is evident that there is comparatively 

 little relation between response and total requirements in the 

 case of plant food, and that something more than a knowledge 

 of the chemical composition of the fruit and wood is needed 

 before one can properly fertilize an orchard. Even with the 

 additional knowledge of the composition of the soil, the prob- 

 lem is not much simplified, because it is impossible as yet to 

 duplicate sufficiently the conditions existing in any soil. A 

 chemist may determine the total amounts of plant food present, 

 but he can not yet determine their actual availability to the 

 trees with sufficient accuracy to be of much value. 



The practical and proper fertilization of an orchard, there- 

 fore, becomes an experimental problem. The first stage of 

 this problem involves general experiments for the purpose of 

 developing the most promising application for general use, 

 where fertilizers seem to be needed. This general formula 

 can then be adjusted to the exact needs of the particular orchard 

 involved, by means of a local testing plan. Our present data 

 on these questions are as follows : 



Rates and Methods of Application. — The rates of applica- 

 tion that we have been using in the series of experiments in 

 Pennsylvania are as follows : Actual nitrogen, 50 pounds per 

 acre, carried about half in dried blood and half in nitrate of 

 soda; actual phosphoric acid (P^Os), 100 pounds, carried in 

 acid phosphate, with "floats" and recently basic slag used in 

 certain plats for comparison; Potash (K-O), 150 pounds, car- 

 ried at present in the high-grade muriate, with the high-grade 

 sulphate and recently also the low-grade sulphate used in com- 

 parison in certain experiments. The manure is applied at the 

 rate of 12 tons per acre, and the lime at 1000 pounds per acre. 

 All applications are made annually. In the Johnston and 

 Brown experiments considered below, the fertilizers are not 

 cultivated into the soil, but are simply spread over the surface 

 and left to be carried in by the rains. They are cultivated in 

 the Tyson experiment. All fertilizer applications are made 

 somewhat after petals fall, but the manure is put on any time 

 during the spring. 



