730 ANNUAL REPORT OF THE Off. Doc. 



our methods of culture is very large." la Wiscousin, Professor 

 King has found that 422 tons of water are required to produce one 

 ton of dry matter in the potato. 



Control of Moisture. — The first tillage in the potato field is to kill 

 weeds and to break the crust. A single deep cultivation, close to the 

 plants, is advisable for most soils, when all the plants are fully above 

 ground, to insure looseness of the soil in the row. The tramping by 

 horses and men in the middles makes a deep cultivation of the mid- 

 dles, with the long, narrow shovels of the wheel-cultivator, desirable. 

 It should be given at the time of the deep working next the plants. 

 All has now been done that can be done with cultivators to insure 

 a crop, excepting the stirring of the surface to conserve moisture 

 and prevent weed growth. But these surface stirrings are an im- 

 portant part of potato culture. tSome Stations have conducted ex- 

 periments to determine the number of cultivations that is best for 

 potatoes, but a moment's consideration should show their lack of 

 special value. 



There is no certain number of times to cultivate potatoes. All de- 

 pends upon the soil and season. It may pay to stir the soil twice 

 in one week. It may not pay to stir it for ten days. ^Vhen a crust is 

 forming, or when the soil mulch is settling down solid so that 

 moisture evidently is escaping, tillage is needed in the event of 

 probable drouth. If abundant rain follows, the gain from the til- 

 lage can be only slight, but no one can forsee the weather conditions, 

 and experience has demonstrated the profitableness of conserving 

 the moisture we have in the soil. 



The Source of Our Best Moisture. — Some people seem to have the 

 impression that they should look to the clouds during the summer 

 as the one source of moisture for growing crops. The fact is that 

 the best source of supply of water for a summer crop is the rains of 

 winter and early spring. I do not say that this is the chief source, 

 but it is the best one because it is measurably within our control. 

 The water that falls in the winter and spring, going down into the 

 ground and coming back in time of drouth, is that with which we 

 should most concern ourselves. It is our store at hand, and with the 

 clouds we can not deal. The soil is a great sponge for the holding 

 of water. When it is deeply plowed and full of humus, it drinks up 

 the water from snows and rains, and that water passes down into the 

 subsoil. One of the chief offices of tillage is to make soil receptive 

 of rainfall and retentive of moisture. The water in the soil is mov- 

 ing all the time. WTien there is more of it at the surface than there 

 is below, the water descends. This is observable immediately after 

 a summer shower when we find that the plant roots remain unmoist- 

 ened for a time, but know that the next morning will find the soil 

 about them made darker by the moisture that has descended. On 



