Climate, Soils and Rotation 107 



case with potatoes, naturally govern the choice of others 

 to a great extent. The degree of its adaptability to soil 

 and climate, ability to fit into rotation with other crops, 

 money value, net increase or decrease in soil- fertility, and 

 cost of growing are all to be considered. 



ROTATION 



It is seldom desirable to grow the potato continuously 

 on the same soil. The reasons for the rotation of the 

 potato with other crops are : (1) Plant diseases often 

 rapidly become worse when crops are grown continuously. 

 This has often been the case with the potato. Modern 

 scientific methods of care of seed, selection, disinfection, 

 spraying and other details of culture somewhat r.educe 

 this danger. (2) In the business management of the 

 farm, rotation reduces the danger of excessive losses in 

 seasons of low prices or of poor yields, and arranges the 

 work of the farm through the season to better advantage. 

 (3) Weeds are easier controlled under a system of rota- 

 tion. Those which flourish under the conditions of 

 growth of one crop may be easily kept down under an- 

 other. The high value of the potato crop pays for 

 thorough tillage and care which cleans the soil of weeds 

 for the rest of the rotation. (4) Insect pests are kept 

 down easier under rotation. (5) The high cash value of 

 potatoes justifies considerable sums of money spent on 

 fertihzers and enables more of the time of the rotation 

 to be used in producing organic matter to be returned 

 later to the soil. The thorough culture, late digging and 

 winter exposure of soil after potatoes in the northern 

 states rapidly uses up the soil organic matter. The 

 cheapest and easiest way of replacement is by rotation 



