WEIGHT OF ROOTS LEFT IN THE SOIL. 423 



• 



ing, to v/hich are naturally attached Ifce largest weight of roots. Hence, 

 the main reason why poor lands are so much benefitted by being laid 

 down to grass, and why an intermediate crop of clover is often as benefi- 

 cial to the after-crop of corn as if the land had lain in naked fallow. (If 

 the third crop be ploughed in, the land is actually enriched.-^S'cAu-er^^;.) 

 An interesting series of experiments on the relative weights of the 

 roots and of the green leaves and stems of various grasses, made by 

 Hlubek, (Erniihrung der Pflanzen, p. 466,) throws considerable light 

 upon their relative efficacy in enriching the soil by the vegetable mat- 

 ter they diffuse through it in the form of roots. The grasses were 

 grown in beds of equal size (180 square feet) in the agricultural gar- 

 den at Laybach, and mowt: on the fourth year after sowing, just as 

 they were coming into flower. The roots were then carefully taken 

 up, washed, and dried. The results were as follows : 



Weight of 

 > Produce in Produce in Roots, dry Roots 



. Kind of Grass. . • . , " > to 100 lbs. 



Grass. Ilay. Fresh. Dry. of Hay. 



1. FestucaElatior— TVzZZi^esc^ig-^ross.. 124 lbs. 36 lbs. 56 lbs. 22 lbs. 61 lbs. 



2. Festuca Ovina — Sheep's Fescue-grass. 90 30 — 80 266 



3. Fhleum Pratense— Tm^^ay-^mss... 90 25 56 17 60 



4. Dactylis Glomerata — Rough Cock's- , 



foot... 202 67 — 22i 33 



5. Lolium Perenne — Peremdal Rye- 



grass 50 17 — 50 300 



6. Alopecurus Pratensis— Mmrf/?M? Fox- 



toAl 106 35 — 24 70 



7. Triticum Repens — Creeping Couch 



or Quicken-grass 120 60 — , 70 116 



8. Poa Annua — Annual Meadow grass. — — — — 111 



9. Bromus Mollis and Racemosus — 



Soft and smooth Drovie-grass — — — — 105 



10. Anthoxanthum Odoratum — Sweet- 

 scented Vernal- grass — — — — 93 



A mixture of white clover, of ribwort, of hoary plantain, and of 

 couch-grass, in an old pasture field, gave 400 lbs. of dry roots to 100 

 lbs. of hay — and in a clover field, at the end of the second year, the 

 fresh roots were equal to one-third of the whole weight of green clo- 

 ver obtained at three cuttings — one in the first, and two in the second 

 year — while in the dry state there were 56 lbs. of dry roots to every 

 100 lbs. of clover hay which had been carried off. 



The fourth column of the above table shows how large a quantity of 

 vegetable matter some of the grasses impart to the soil, and yet how un- 

 like the different grasses are in this respect. The sheep's-fescue and 

 the perennial rye-grass — besides the dead roots, which detach them- 

 selves from time to time — leave, at the end of the fourth year, a weight 

 of living roots in the soil which is equal to three times the produce of 

 that year in hay. If we take the mean of all the above grasses as an 

 average of what we may fairly expect in a grass field — then the amount 

 of living roots left in the soil when afour-year-old grass fieldis plough- 

 ed up, will be equal to one-sixth more than the weight of that yearns crop. 



In an old pasture or meadow fie.d again, when ploughed up^ the 

 living roots left are epual to four times the weight of that yearns hay 



