Climate, Soils and Rotation 87 



States because of its high value for human food, not be- 

 cause of favorable conditions. These facts are emphasized 

 because knowledge of the nature of the potato plant helps 

 the grower to adapt his methods to his local conditions 

 to secure the best results. Except in northern Maine 

 and the adjoining provinces of Canada, there are few 

 parts of America where summer heat and moisture do not 

 limit the yield of the potato to a figure below the best 

 possibilities of the plant. Methods which prevent the 

 effects of these two factors result in largely increased 

 yields. In occasional seasons, as in parts of New York 

 in 1909 and 1914, the climate is favorable and large yields 

 are grown. It might be possible in such years to get 

 yields equal to those of northwestern Europe, but it 

 would be necessary to equal their large expenses for addi- 

 tional labor, seed and fertilization and this would result 

 in heavy loss in the other years when climate limited the 

 yield. Hot and dry years are known in Europe, but are 

 the exception instead of being the rule as in most of the 

 United States. 



The United States Department of Agriculture Year- 

 book for 1914 gives the average yield of potatoes to the 

 acre for the whole United States for ten years as being 

 96 bushels, while that of the state of Maine, with cool and 

 damp climate, for the same period, was 206 bushels. 

 The figures for the countries of northwestern Europe are 

 311 for the Netherlands, 388 for Belgium, 210 for Great 

 Britain and Ireland and 200 for Germany. Yields are 

 lower in the warmer or drier countries of Europe, being 

 130 in France, 115 in Hungary and 106 in Russia. A 

 similar contrast is marked between hot Australia with an 

 average of 101 bushels and cool New Zealand with 216, 

 though both are settled by the same race of people. 



