486 ANNUAL REPORT OF THE Off. Doc. 



the danger is very much less, and in fact ordinarily quite remote. 

 Hence, in the discussion of the subject the influence of the season 

 of growth of the plants is worthy of consideration. If the crop 

 which is intended for green manure matures rather early in spring, 

 then the time of plowing under must be governed by the purpose 

 of the growth of the crop which follows, as its development will 

 be materially influenced by the operation. Take, for example, rye, 

 representing the class of ^'nitrogen consumers." This crop makes 

 a rapid, early development, and if allowed to entirely mature it 

 not only draws heavily upon the available food constituents of the 

 surface soil, but rapidly and often completely exhausts it of mois- 

 ture. Hence, if plow^ed down in its mature state it will result in 

 leaving a mass of vegetable matter not readily decayed between the 

 surface and the subsoil, thus cutting off absolutely the connection 

 between the surface and the reservoir of water lying below. 

 Should, therefore, dry weather follow, the decay will be very slow 

 and the succeeding crop will have only the food and the moisture 

 that are contained in the surface soil turned over, and from this 

 the available food and the moisture have been largely extracted 

 by the maturing of the large crop of rye. 



Spring Green Manure Crops. 



Hence, it is readily seen that the time of plowing down the green 

 crop is a matter of the very greatest importance. Rye is an ex- 

 cellent green manure, if properly used. It should, therefore, be 

 plowed down not later than when just coming into head, when the 

 vegetable matter is immature, which readily breaks down and 

 decays, and when the smaller growth of the plant has made but 

 little demand upon the soil for moisture. Furthermore, in this 

 early stage of growth the vegetable matter does not make so bulky 

 a mass between the surface and subsoil, and thus the capillary con- 

 nections between the upper and lower layers are readily made, 

 and hence not preventiog the next crop from securing its needed 

 moisture. 



The principles involved here are practically the same for crops 

 of a leguminous character. For example, crimson clover, which 

 has been seeded in corn, or that has been seeded in orchards for 

 the purpose of accumulating nitrogen, also prevents mechanical 

 losses and contributes to the improvement of the physical character 

 of the soil. Still, the time of plowing down the crop is of the very 

 greatest importance, not only in its influence upon the character of 

 the soil itself, but upon the growth of the subsequent crop. Should 

 the crop mature, and the weather conditions be entirely favorable, 

 and there is sufficient moisture and warmth, then no danger may be 



