686 ANNUAL. REPORT OF THE Off. Doc. 



It is an old belief of growers that the potato is, in a peculiar de- 

 gree, a feeder upon potash. It resulted that all special potato fer- 

 tilizers a decade ago made potash the most prominent element. 

 There is a reason for most things under the sun, and, in casting about 

 lor the cause of this confidence that the potato wanted potash chiefly, 

 I am led to think that it arises in part from the known lack of potash 

 in most sandy soils which have been devoted to potato-growing. On 

 these soils applications of potash have been effective. It is further 

 true that the ash of the potato is rich in potash, but in no higher de- 

 gree than is the ash of some other crops. The New York Experiment 

 Station, at Geneva, after a six years series of fertilizer experiments 

 with potatoes, concludes that ''this crop is not greatly unlike many 

 others, including roots and forage crops, in its fertilizer requirements 

 under given conditions." 



It is known that sandy soils incline to be deficient in potash, and 

 extensive growers of potatoes in such soils of Long Island, New 

 York, use potash freely, having in common use a formula calling for 

 four per cent, of nitrogen, eight per cent, of phosphoric acid and ten 

 per cent, of potash. The correctness of this so-called Long Island 

 formula naturally would be accepted for land of that class by reason 

 of its general use were it not for the results gotten in the series of 

 tests made by the Geneva Station under direction of Dr. Jordan. 

 Very strangely the potash was wholly ineffective in some of these 

 tests, and Dr. Jordan says: "'The outcome of extensive experiments 

 for four years on four farms presents good reasons for questioning 

 the wisdom, under the condition involved, of applying more potash 

 on potatoes than any other ingredient. It is now a trite saying, but 

 a true one, that each farmer must discover for himself the fertilizer 

 needs of his farm." 



Nitrogen. — Within certain lines we may infer pretty safely the 

 nitrogen requirements of our potato soils. Land that is very rich in 

 humus, such as black alluvial soil, is rich in nitrogen. This 

 element is the most costly one in a fertilizer, and an unnecessary ap 

 plication cuts net profits rapidly. Stable manure, made on cement 

 or tight clay floors, and kept without waste until spread upon the 

 land, is rich in nitrogen. Where a soil is liberally fed with stable 

 manure the year previous to the planting of potatoes, we infer that 

 the need of purchased nitrogen is slight. The presence of a good 

 growth of any of the legumes is assurance of the presence of this 

 element. In a soil rich in humus the clover may feed largely upon 

 soil nitrogen, while under other circumstances it may get a goodly 

 share of its supply from the air, but in either case the nitrogen is at 

 hand if the clover or peas is present, and the percentage of nitrogen 

 in the commercial fertilizer may be kept small under ordinary con- 

 ditions. 



Again, we learn to determine the content of nitrogen in a soil by 

 humus, suoh as much black alluvial soil, is rich in nitrogen. This 



