MANURING AND FERTILIZING 35 



garded as being of less importance than potash. The 

 results obtained at the Ohio Station ' show that phos- 

 phoric acid is the most essential fertilizer for their con- 

 ditions, some potash, and, in some cases, nitrogen, being 

 also required. I found the same to be true at Briar- 

 cliff Manor, N. Y., where 100 pounds of available 

 phosphoric acid per acre (equal to 600 pounds acid 

 phosphate, 16-17 per cent, available) gave profitable 

 returns. My own observations are that an excessive 

 application of available phosphoric acid has a marked 

 influence upon the foliage, causing it to be small, dark 

 green, wrinkled, and apparently stunted in develop- 

 ment, with consequently early maturity. In some 

 cases the period of growth is reduced six or eight 

 weeks, and consequently the yield is low; but, owing 

 to the potatoes being mature, the quality is generally 

 good. In certain localities, for early potatoes, where 

 it is desirable to hasten maturity, the use of fair quan- 

 tities of acid phosphate, with a limited suppl}^ of nitro- 

 gen and potash and no barn manure, is found to be 

 good pradlice. The nitrogen ma}^ be supplied in an 

 available form as nitrate of soda, since nitrification 

 may not be a6live in the soil during the early period 

 of growth. 



The Influence of Calcium. — Calcium does not aip- 

 pear to be so important as some of the other elements, 

 although in some cases it produces a marked increase 

 in yield (Fig. 10). If applied in a form which has 

 an alkaline acflion upon the soil — as, carbonate of 

 lime or quicklime — it may have an injurious effedl by 



'Ohio Bui. 125, pp. 131, 132. 



