MANURING AND FERTILIZING 35 



garded as being of less importance than pot-ash. 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 supply of nitro- 

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

 good practice. The nitrogen may be supplied in an 

 available form as nitrate of .soda, since nitrification 

 may not be active in the soil during the early period 

 of growth. 



The Influence of Calcium. Calcium does not ap- 

 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 action upon the soil as, carbonate of 

 lime or quicklime it may have an injurious effect by 



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



