ROT 



RUB 



NO. 6, QUATRENNIAL ROTATION ADOPTED BY M. CKUD. 



SUMMARY. 



" From all that precedes, it is ob- 

 vious that rotations which include 

 trefoils, red clover, lucern, and sain- 

 foin are those that aflbrd considera- 

 bly the largest proportion of organic 

 matter ; a fact, indeed, which, if not 

 legitimately estal)lisl)ed, has still been 

 long acted on in that system of crop- 

 ping which embraces forage plants 

 as an element. Lucerns, too, when 

 they have taken kindly, yield an ex- 

 traordinary quantity of forage, as ev- 

 ery one may see by turning to the 

 produce of the piece under tliat crop 

 which, in the system of M. Crud, suc- 

 ceeds the quatrennial rotation. At 

 the end of his rotation. M. Crud al- 

 ways lays on manure in the ratio of 

 18 tons per acre, which lasts fm^ six 

 years, and may be said to sulTice for 

 the succession of crops in the ap- 



Gain in azote per annum and per acre 130 



" In glancing at these tables, it is 

 obvious that the azote of the crop al- 

 ways exceeds the azote of the ma- 

 nure. Generally speaking, I admit 

 676 



that this excess of azote is derived 

 from the atmosphere ; but I do not 

 pretend to say in what precise man- 

 ner the assimilation takes place. I 

 shall only quote the conclusion of a 

 paper which I published on the sub- 

 ject in the year 1837. Azote may 

 enter immediately into the constitu- 

 tion of vegetables, provided their 

 green parts have the power of fixing 

 it ; azote may also enter vegetaliles 

 dissolved in the water which bathes 

 their roots, and which always con- 

 tains it in a certain proportion. Last- 

 ly, it is possible that the air may con- 

 tain an infinitely minute quantity of 

 ammoniacal vapour, as some natural 

 philosophers have maintained, and 

 tliat this, assimilated, decomposed, 

 and rccomposed anew by the plant, 

 is the source of its azotized constit- 

 uents.'* 



ROTTEN STONE. A soft alu- 

 minous mineral used in polishing met- 

 als. 



ROUP. A disease of Poultry, 

 which see. 



ROWAN-TREE. The mountain 

 ash {Pyrus aucvparia). 



ROWEL. A seton ; also the sharp 

 wheel of a spur. 



ROW'EN. A name for after-math 

 hay. 



RUBEFACIENTS. Substances 

 which produce redness on the skin 

 without blistering. 



