394 



KNOWLEDGE. 



October, 1910. 



method appears to have originated in Erance. where 

 M. Bonnet found,"* about 1896, that a soUition of 



copper sulphate 

 destroyed char- 

 lock (Siuapis 

 arveiisifi L.) 

 without per- 

 manentK- injur- 

 in;; the cereal 

 crop among 

 which it grew.+ 

 Attentiiin was 

 directed to this 

 f act in the 

 English press, 

 and a host of 

 e X p e r i m e ii t a 1 

 trials were sucin 

 conducted, the 

 result being 

 that the facts 

 were (juickh' 

 established, 

 and in 1900 a 

 leaflet on the 

 destruction of 

 charlock b y 

 means of spray- 

 ing with the 

 siilphatt'S (if 

 iron anil copper 

 was issued by 

 the Board of 

 ■\ g r i c u 1 1 u r e . 

 Eort\' gallons 

 of a 4 per cent, 

 solution of co[)- 



FlGURE 7. 



Spiirri'v I SpcrgiiJii arvciisis L.) ' j. 



This ]ilaiit is one of the most tnmbk'soine 



weeds on lii,'ht s^ndy soils. Being an 



annual it is only neeessary to prevent the 



ripening of seed. It has been found that i u f 



a 5 per cent, .solution of copper sulphate P^"'' sinpnate, or 



destroys it. a 15 jier cent. 



solution of iron 



sulphate, ma\' be sprayed over an acre of the crop 



when the charlock is about three inches high, and if 



the operation be projierh- performed during suitable 



weather, the weed will be destroyed and the cereal 



remain practically uninjured. 



It is believed that the rough, broad, more or less 

 horizontal leaves of charlock catch and retain the 

 solution, while the narrow, smrxjth, ])ractically 

 vertical leaves of the cereal throw it off, and hence 

 are not damaged. In this connection there is 

 room for further investigation, and it may be com- 

 mended to the chemist and botanist alike as a source 

 of interesting research. 



Since the introduction of spra\'ing for the 

 destruction of charlock, a number of experiments 

 have been carried out by man^• in\'estigators, who 

 have made trials with a variety of plant poisons, the 



effects of which have been obser\'ed when applied to 

 a number of species of plants. Though the results 

 are interesting and some information has been 

 obtained, they are by no means conclusive, but it 

 will be useful to refer here to some of the experi- 

 ments and their results. 



In the course of experiment, d wurk ui spra\'ing 

 charlock (Eigure 1) with iron sulphate, in 1898, it 

 was found by Professor Somerville+ that both at the 

 Northumberland County F"arm, Cockle Park, and in 

 the grounds of the Durham College of Science 

 (Newcastle-on-T\'ne), all rough-leaved plants, such 

 as thistles, and, to a lesser extent, coltsfoot 

 (Tiissila^o Farfaid L.), were crippled ; while 

 glaucous plants, like species of Chcnopodiiiin, were 

 not affected. 



It is w'vW known that broad-leaved plants are 

 often scorchctl when nitrate of soda is broadcasted 



Figure 8. 



Black Bindweed. I Polyfioniiiii Convolvulus L.) 

 X ?,. A most mischievous annual, the twining 

 branches of which may be several feet long and 

 drag down cereal and other crops. Partly destroyed 

 by spraying with copper and iron sulphates, seeding 

 being largely prevented. 



on them. It was stated ten years ago!; that a 

 solution of 15 to 40 per cent, of nitrate of soda and 



1 As noted licln«-. Ml 



Jiiiini. {l'A}^iic. I'lcifujiic. l.S>)7. 



H. L. Bolley started spraying investigations in the I'liiled States in 1,S')6, and says they were perhaps 

 the first experiments of the kind conducted in any country. 



I The Field, July 'Jth, 189«. j The Times, October 8th, 1900. 



