No. 6. DEPARTMENT OF AGRICULTURE. 467 



understood. Its best use is in the preparation of the soil for seed- 

 ing by mashing lumps and clods, in solidifying it and making it fine 

 and friable. If used after seeding, it compacts the soil and leaves 

 the surface smooth, thus providing the very best conditions for the 

 rapid movement of air over the surface and, therefore, causing the 

 ready abstraction of the moisture from it. It should not be freely 

 used on heavy clay soils that are often already sufficiently finely 

 divided and which are liable to become too much compacted, even 

 under natural conditions, but rather upon open soils, those that are 

 of a loose nature, as sandy and gravelly, in order that the particles 

 may be pressed closer together, and thus to prevent the rapid es- 

 cape of the water. Nevertheless, in dry seasons the roller is use- 

 ful at time of seeding, because the compacted surface and the 

 greater evaporation therefrom cause a rapid drawing up of the 

 water from the lower layers to the surface of the soil, enabling a 

 quicker germination and a more rapid early growth. In other 

 words, the rolling tends to draw the moisture from the lower layers 

 to the surface layer, and its use can be recommended after seeding 

 under the conditions named. The roller should be used during the 

 preparation of the soil, and if used after seeding the surface should 

 be again stirred by a harrow, which makes a light soil mulch, or 

 after it has performed its function in making fine and friable the 

 seed-bed. 



In order to guide the farmer in respect to the application of the 

 general principles here laid down, the following general suggestions 

 are made. 



When to Plow. 



It has already been pointed out that plowing aids in the conser- 

 vation of soil moisture. The question that naturally arises first, 

 is what time shall plowing be performed in order to obtain the best 

 results. It is obvious that for certain crops, as winter wheat or 

 fall seeding of any sort plowing must be done in summer or early 

 autumn, unless the land is fallowed, whereas for spring planted 

 crops, as Indian corn, spring wheat, oats, barley and a number of 

 others, it does not necessarily follow that plowing shall be done in 

 the spring; fall plowing for these presents many advantages, though 

 there are also disadvantages, and these must be carefully weighed 

 before the practice is adopted. For example, the ideal condition 

 of soil during winter is to have it occupied by a growing crop, be- 

 cause in this condition it readily absorbs and holds the moisture 

 and prevents, in large measure, losses that occur through drainage 

 from it of the soluble plant-food constituents, still the effect of 

 freezing and thawing, and of oxidation, which take place when land 



