10 CIRCULAR NO. 122, BUREAU OF PLANT INDUSTRY. 



tative growth, is likely to cause serious injury later. For those desir- 

 ing to experiment with fertilizers the following acid mixture is rec- 

 ommended, applied at the rate of 1,000 pounds per acre, or one-fifth 

 of a pound per square yard : 



Pounds. 

 Acid iibosiiliate (liigli grade, about 36 per cent available pbosphoric 

 acid) — 600 



Sulpbate of potasb (50 per cent potash) 200 



Sulphate of ammonia (20 per cent nitrogen) 200 



(Muriate of potash may be substituted for sulphate of potash.) 



This and similar acid mixtures have been used with success on blue- 

 berry plants, in both pot and field experiments, wdth no evidence thus 

 far of cumulative injurious effects. However, as no fertilizer is re- 

 quired to make the swamp blueberry fruit abundantly and continu- 

 ously in suitable peat and sand soils properly handled, the use of fer- 

 tilizers in commercial plantations is not at present advocated. 



The swamp blueberry does not require a yearly pruning. A^^ien 

 one of the stems of a bush becomes unproductive from injury or old 

 age it should, of course, be cut out. If a large part of a bush needs 

 removal it is better to cut all the stems to the ground and let the plant 

 send up new shoots all of the same age to form a Avholly new and 

 symmetrical top. 



YIELD AND PROFITS. 



By proper manipulation in the greenhouse, seedling blueberry 

 plants can often be made to ripen a few^ berries in less than a year, 

 but they do not come into commercial bearing in field plantations 

 until they are about 5 years old, when the plants are 3 to 4 feet high. 

 They then increase slowly to full size and full bearing. Wild bushes 

 of the swamp blueberry live to great age, often 50 to 100 years, still 

 bearing heavily. Individual stems may remain productive for 10 to 

 25 years. When dead they are replaced by new and vigorous shoots 

 from the root. 



The field plantings resulting from the recent experiments in blue- 

 berry culture are too young to show the mature yield. Fortunately, 

 however, there has been found, near P^lkhart, Ind., a small blueberry 

 planting of mature age, believed to be the only commercial plantation 

 in existence. The returns from this plantation set forward our 

 knowdedge of yields by at least a decade. The plantation is a little 

 less than 2^ acres in extent. It was started in 1889 in a natural blue- 

 berry bog, wdiich was first drained and then set with unselected wild 

 l>luel)erry bushes. The plantation was profitable from the first, but 

 exact records of yield and receipts are available only for the years 



tCir. 121.'] 



