THE FARMER'S MAGAZINE. 



183 



implements, have accomplished great things in this 

 war of extermination ; but wc all feel that still 

 greater advances are yet to be made . Science has 

 of late done good service in tiic cause. The men 

 who grace the staff of the Agricultural Coliege of 

 Cirencester have well led the way, of late, in the in- 

 vestigation. Professor Buckmau has traced their 

 habits, and some of the effects of different modes of 

 cultivation on the growth of the weeds of different 

 soils ; and, still more recently, Professor Voelcker 

 (Journal Roy. Ag. Soc, vol. xviii., p. 350) has given, 

 amongst other valuable matters relating to the sub- 

 ject of this paper, the analysis of two of the more 

 common weeds of the cereal soils — the stemless 

 thistle and the couch. His results will be read with 

 deep interest by many of my readers, who, as I de- 

 scribed in this magazine for last month, are in many 

 places now collecting their weeds into heaps, and 

 reducing them to an enriching compost by copious 

 additions of common salt or lime. 



Professor Voelcker tells us that he selected these 

 two weeds for examination, since they so very gene- 

 rally infest the calcareous clay soils and brashy 

 lands of the Cotswold Hills ; but many a farmer, 

 who will read the result of his inquiries far away 

 from the oolite formation, is equally haunted by 

 these unwelcome visitors. 



The stemless thistle (Carduus acaulis), when 

 examined as just gathered, contained from 25 to 26 

 per cent, of dry substance, and 74; to 75 per cent, of 

 water. When burnt, the plant yielded 9.60 per 

 cent, of ash. In 100 parts of this ash (and this is 

 the important portion of the inquiry) was found: 



Potash and chloride of potassium 27'40 



Common salt "90 



Lime 41 '44 



Magnesia 4*40 



Oxide of iron and alumina 2"01 



Phosphoric acid .,^,., 5"3G 



Sulphuric acid 2'92 



Soluble silica and sand ........ 3'50 



Carbonic acid, and loss 12.07 



The large proportion of lime which this ash con- 

 tains, the Professor considers, may account for the 

 fact that this thistle delights in the calcareous 

 formation of Gloucestershire. Toe amount of 

 phosphoric acid which it yields is by no means 

 inconsiderable; and this is evidently united with 

 lime, as phosphate of lime. 



Of still more general interest to the farmer is the 

 analysis of the widely-diffused couch-grass, which 

 ever seems to haunt arable soils, and to follow, as it 

 were, the wheels of the plough. The couch exa- 

 mined ill the laboratory at Cirencester, on being 

 burnt, furnishei an ash coloured slightly red by 

 oxide of iron, derived, no doubt, from the adhering 

 clay. These were found by Mr. Kensington to 

 confain, per cent. : 



Potash 10'02 



Soda 5-69 



Common salt 3"34 



Lime 5"58 



Magnesia '04 



O.xides of iron and alumina 12'40 



Phosphoric acid.. .. „„ 9"38 



Sulphuric acid , 5'33 



Soluble silica 24-92 



Insoluble silicious matter (chiefly sand) 17'50 

 Carbonic acid, and loss 5 80 



These constituents, the Professor considers, are 

 probably united in the couch-ash as follows : — 



Per Cent. 



Carbonate of potash 14<'10 



Potash in a state of silicate 0'27 



Soda in a state of silicate 5"69 



Common salt 3'34 



Oxides of iron and alumina 12'4:0 



United with phosphoric acid (equal to 



bone-earth 2032) 9-38 



Sulphate of lime 9"06 



Carbonate of lime 3'30 



Magnesia in a state of silicate 0'04 



Soluble silica 24-92 



Insoluble silicious sand 1 7'50 



The ash of the couch, adds Mr. Voelcker, it will be 

 seen, differs in several respects from that of the stem- 

 less thistle : the latter contained teut little silica, 

 whilst soluble silica is the chief constituent of couch. 

 Again , the proportions of lime and potash in the 

 thistle are much larger than in couch ; an interesting 

 fact, on account of both weeds having been collected 

 from soils of a similar character. This is quite con- 

 sistent with our present information on the par- 

 ticular wants of different families of plants. Thistles 

 are evidently lime and potash plants ; and couch 

 appears to require much soluble sdicaforits growth, 

 a fact which perhaps will explain its occurrence in 

 sandy, as well as in calcareous and clay soils. The 

 two last-mentioned soils often, it is true, do not con- 

 tain any silica, in the shape of sand, capable of being 

 mechanically separated from the constituents of 

 other soils ; but most clay soils are rich in alkaline 

 silicates, from which plants unquestionably can take 

 up soluble silica much more readily than from sand. 



The large proportion of phosphoric acid in couch- 

 grass, as the Professor adds, likewise deserves to be 

 specially noticed. United with lime, we have no 

 less than 20 per cent, of bone-earth in couch-ash ; a 

 circumstance which throws some light on the ex- 

 perience of many Gloucestershire farmers, who ob- 

 serve. That the fouler the laud is, the better will be 

 the crop of turnips, grown without any other manure 

 than the ashes produced by paring and burning the 

 land. " I remember," observes the Professor, 

 " having once walked over a very foul piece of land full 

 of couch, and was not a little amused by the remark of 

 my agricultural friend who accompanied me, ' What 

 fine healthy couch, sir ! It will give me next year, 

 I don't doubt, a splendid crop of roots, although I 

 do not mean to put a single load of manure on this 

 land.' Indeed," concludes the Professor, "I have 

 ascertained that a much larger proportion of bone- 

 earth is brought within reach of the turnip plant, in 

 the red ashes obtained on paring and burning, than 

 is contained in a heavy dressing of bone-dust." 



These practical observations of the heavy-soil- 

 farmer, as to the fertilizing effects of a good crop of 

 couch-grass, I rather incline to the opinion, arc well 

 worthy of far more extended investigation than they 

 have yet received. 



The observation, that where there is a good crop 

 of couch, that there a good crop of turnips may be 



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