36 



able that the excess of phosphoric acid is valuable to the crop. There 

 is no evidence, however, to show that the potato crop is benefited 

 by such a great excess of potash. It would seem that if 1,500 pounds 

 of a high-grade fertilizer is to be used, one carrying 6 or 7 per cent 

 of potash in place of the 10 would be better balanced. 



The Forvi of Fertilizing Ingredients. 

 In 1907 a high-grade jDOtato fertilizer was used in large quantities, 

 in Maine, on potatoes, which did not carry any nitrate nitrogen. 

 There was quite a general conijjlaint as regards failure with this 

 particular fertilizer, and much dissatisfaction, leading even to the 

 threatening of law suits, because of the short crops supposedly due 

 to this fertihzer. Careful examination of this fertilizer showed that 

 its constituents were all high grade, and that, while it fell somewhat 

 below its guaranteed analysis, it still was high-grade goods. The 

 dissatisfaction and poor results from the use of this fertilizer were 

 probably due to the absence of nitrate nitrogen. The grower in 

 a climate where the growing season is so short must see to it that 

 the fertilizer used, and particularly on the money crop, carries a fair 

 proportion of its nitrogen in the form of nitrate nitrogen. Fully a 

 third of the nitrogen in a fertilizer carrying 3.3 per cent nitrogen 

 could with safety be in the form of nitrate. It would not do to have 

 much more than that in the form of nitrate, because of the danger 

 of loss from leaching out by heavy rains. From field experiments 

 conducted by the Maine Experiment Station, it is not advisable to 

 have much, particularly of dry mixed, hone tankage in the fertilizer, 

 as it seems to stimulate the growth of the tops too late in the season. 

 Where one can know relative to the source of the nitrogen, it is probably 

 desirable to have about a third as nitrate nitrogen, and the rest in the 

 form of dried blood or high-grade tankage. Sulphate of ammonia 

 is a good source of nitrogen, becoming available more quickly than 

 tankage, but is not as immediately available as nitrate of soda. While 

 it is water soluble, there is not nearly the danger of loss by leaching 

 as there is with the nitrate. It matters little whether the phosphoric 

 acid is from bone or from rock phosphate; but it is necessary that 

 in any case it be acid-treated, so as to be in the available form. There 

 seems to be no difficulty as to the form of phosphoric acid and its 

 availability in any of the high-grade fertilizers offered in New Eng- 

 land. With certain crops, sulphate of potash gives better results 

 than does muriate, and there is more or less of a general opinion 

 that sulphate of potash produces better quality of potatoes. There 

 is, however, very little evidence to support this conclusion. Practi- 

 cally all the potash in New England sold fertilizers is in the form of 

 muriate or sulphate, and it seems to make little difference which 

 form of these two is used. 



Amount oj Plant Food per Acre. 



Even on soil of high fertility, it is found profitable to fertilize liberallj''. 

 For a large crop, the fertilizer should carry not less than TjO or 60 

 pounds of nitrogen, one-third of which should be in the form of nitrate, 

 not less than 60 pounds of available phosphoric acid and not less than 

 100 pounds of potash. About two-thirds of this can best be applied 

 in the drill at time of planting and the rest at first or second culti- 

 vation. 



To most Massachusetts farmers this amount of plant food for the 

 potato will appear excessive, but it is found profitable in practice. 



