62 MASSACHUSETTS HORTICULTURAL SOCIETY. 



the advice : First, use all the manure that is produced on the farm ; 

 then, since most farmers in the older states need something more, 

 experiment to ascertain what fertilizers produce the best effect. 

 AVhoeverwill use fertilizers economical]}' and profitably, must select 

 the ones that supply- the materials which his particular crops need, 

 and his soil fails to furnish. And the question what is most needed 

 in a given case, can be tested in no better way, — indeed, in no 

 other way than by direct experiment, — b}' putting the question to 

 the soil with the fertilizers, and getting the answer with the crops. 

 Of course, the effects of weather, tillage, physical character of the 

 soil, indirect action of the fertilizers, and so on, count for a great 

 deal, and the most reliable results will come only after repeating 

 the experiments for a series of years, through a course of rotation 

 of crops, for instance. 



Leander Wetherell asked how Mr. Birdsey's soil was treated be- 

 fore the experiment. 



Prof. Atwater replied that in that region the farmers had long 

 been in the habit of using a good deal of bone, superphosphates, 

 guano, and fish. These supply phosphoric acid and nitrogen, but 

 little or no potash. Mr. Birdsey says that on this particular soil, 

 bone used to produce an excellent effect, but of late he sees scarcely 

 any benefit from it. It would seem as though this land had become 

 relatively over- charged with phosphoric acid and deficient in 

 potash. 



Benjamin P. Ware spoke of farmers in Danvers who raised 

 large crops of potatoes of superior quality, year after year on the 

 same land, with Peruvian guano, so that the principle has been 

 established that guano does well there. Probably this would not 

 apply to all soils. 



Prof. Atwater saw no reason why this should not be so on 

 farms in Danvers, nor any reason why on others the case should 

 not be different. Phosphoric acid and nitrogen are the ingredients 

 most often lacking in our soils, and are supplied abundantly and 

 economically in Peruvian guano. Prof. Atwater spoke with 

 approval of the process of " rectifying" Peruvian guano, which, as 

 imported, contains large lumps and some stones, and not much 

 sulphuric acid. In rectifying, the stones are removed, the lumps 

 pulverized, and the whole mixed to make it uniform. Sulphuric 

 acid is added, as to bone and mineral phosphate, to make the 

 phosphoric acid more readily soluble and to fix the ammonia. 



