A STUDY OF FACTORS INFLUENCING THE YIELD OF POTATOES 1191 



thru the years 1914 to 1917, inclusive, found practically no advantage 

 for any one form over another. 



Altho many different analyses of fertilizers were used in 1912 and. 1913 

 in the surveyed regions, the majority of growers in each region were 

 buying fertilizers of the same analysis. In table 28 are shown the analyses 

 of the fertilizers in commonest use at that time, in the four regions: 



TABLE 28. COMMONEST ANALYSES OF FERTILIZERS USED IN THE FOUR REGIONS 



SURVEYED 



Because of the higher percentage of nitrogen in the fertilizer used on 

 Long Island, this region has used a higher grade of fertilizer than any of the 

 other regions. The extra nitrogen has been used to maintain this element 

 in view of the heavy draft on it caused by the continuous potato culture. 

 The greater use of manure and sod residue in the other regions has furnished 

 the nitrogen lacking in the additional fertilizer used. Aside from the 

 nitrogen content, the fertilizers used in the four regions have been similar 

 in analysis. 



Method of applying fertilizer 



The method of applying fertilizer to potatoes is a question not well 

 worked out because it is complicated by, and dependent on, such factors 

 as soil type, amount of fertilizer used, and method of planting the crop. 

 The question as treated here relates to (1) the depth of applying the 

 fertilizer relative to the seed pieces, (2) broadcasting as compared with 

 drilling, and (3) time of application relative to time of planting the crop. 

 Obviously, fertilizer should be applied at that depth which will afford it 

 a constant supply of moisture to make it available to the root system of 

 the potato plant. As this ddpth is less in heavy soils than in light soils, 

 both fertilizer and seed are generally applied less deeply in heavy than in 

 light soils. Since the root system of the potato plant normally develops 

 laterally to a radius of from 18 to 24 inches, the question of depth of appli- 

 cation would seem more important than that of whether the application 

 should be by drill or broadcast. The question of time of application must 

 depend on the availability of the fertilizer used and the seasonal distri- 

 bution of rainfall. 



