20 



EXPERIMENT STATION BULLETIN 351 



FIELD CROPS AND FERTILIZERS 



Rotation, Fertility, and Cultural Experiments 

 With Potatoes in Northern New Hampshire 



This project, located on the Coffin farm, near Colebrook, was con- 

 tinued during the past year. However, due to the difficulties of securing 

 nitrogen carriers, it was necessary to omit the comparison of these car- 

 riers as a factor in potato production. A test of the need for more cal- 

 cium was substituted for this phase of the work. 



Accordingly, gvpsum was secured and applied broadcast at three 

 rates, 500, 1000,' and 2000 pounds per acre. The land was harrowed 

 thoroughly and potatoes were planted with uniform fertilization. At 

 harvest time, yields for the different treatments were as follows: 



Although the results represent but one season's work, they are suffi- 

 ciently significant to indicate that calcium or sulphur, or both, are serious- 

 ly deficient on this soil. The w^ork is being repeated in 1943 to see 

 whether similar results are obtained, in which event the need for an ex- 

 pansion in the use of gypsum as a soil amendment in the Colebrook area, 

 and perhaps on other potato soils of the state, would seem apparent. 



Yields resulting from the use of gypsum var\' more widely than 

 those for different fertilizers. Because of the dry w eather the season at 

 Colebrook in 1942 was not ideal for potatoes and xields were about 25 

 per cent below normal. With such a season, differences in yields due to 

 fertilizer variable are usually prett\' well ironed out. This was the case 

 in 1942. 



The table below gives the average yields for various fert*ilizer treat- 

 ments from 1940 to 1942 inclusive. In these treatments, nitrogen was kept 

 at a constant level, while the phosphoric acid and potash were varied. 

 Yield variations for these treatments are so slight as to be well within the 

 limits of error. 



With potatoes showing a rather remarkable response to gypsum, it is 

 quite likely that the need for calcium (or sulphur) is so strong on this 

 field that variations in amounts of other plant foods are overshadowed. 



