SOIL EXHAUSTION AND ROTATION IN CROPS, 97 



ing and washing. The average length of the roots was noted, 

 and the total weight of roots and tops ascertained. Tliis was 

 done, as the table shows, at several different periods of growth. 

 You see from the second column that the roots of rye at 

 the time of heading had an average length of eight inches, 

 and did not gain anything beyond that. In the clover, at the 

 time of budding, their length was eighteen inches ; in bud, 

 sixteen inches. That looks like going back ; but you must 

 remember that the roots measTired in the one case were not 

 the same roots as those measured in the other, but were from 

 another plot of ground. In blossom, they were fourteen and 

 one-half inches; when ripe, fifteen inches. The grand result 

 is simply this : that wherever rye roots were eight inches, 

 clover roots were twice that length ; and this in soils which I 

 suppose were quite similar in character. That is a piece of 

 Information of great value. 



Mr. Lyman. I have heard old men express the opinion 

 that the principal benefit of clover arose from the large 

 amount of root which is left in the ground, even after it is 

 plowed under. I suppose that to be the fact. 

 Phof. Johnson. Undoubtedly so. 



Mr. Lyman. If we grow a plant which has a very small 

 joot, of course the vegetable matter to supply the succeeding 

 crop is comparatively small. 



Prop. Johnson. I have hoard old farmers, and young ones 

 too, say that they would give more for that part of the clover 

 crop below ground than for the part above ground. You 

 have here an accurate setting forth of the proportions. Look 

 at the figures which represent the weight of the top and of the 

 roots. You see there is a rapid increase in the amount of 

 top in the rye plant — from fifty up to two hundred and fifty ; 

 but you observe that the absolute amount of roots diminisiies. 

 Whether that is due to any actual decay of the root, or 

 whether to the fact that each result came from a different 

 plot of ground, or because of different care in extricating the 

 roots from the soil, we have no information. It may be due 

 to the fact that there was less development of root in one 

 place than in another. 

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