AGRICULTURAL BULLETIN.

Press, Volume LXVII, Issue 20169, 23 February 1931, Page 6

AGRICULTURAL BULLETIN.

SODIUM CHLORATE. VALUE AS A WEED-KILLER. The monthly Agricultural Bulletin (No. 20), issued by Canterbury Agricultural College in conjunction with the Canterbury Chamber of Commerce, deals with the subject of the use of sodium chlorate as a weed-killer:— Sodium chlorate has recently risen into a position of great importance in America as a killer of weeds iA arable land, and in New Zealand as a killer of Californian thistle and ragwort in pasture. Historical Review. Potassium chlorate was used on prickly pear in Australia in 1901, without any great success; and the chlorates fell into disuse until a new series of experiments was initiatedjn France sometime before refers to a previous experiment and gives his own results with ammonium chlorate on weeds in grain crops. In 1925 a Danish report was published on the experiments of the preceding three years, and in 1926 Korsmo states that sodium chlorate killed cfleven species of perennial weeds including Californian thistle, and long twitch.' In 1924-1925 Aslander of Cornell (N.Y.) found that chlorates sprayed on growing crops killed annual weeds. In 1927 Latshaw in Kansas found that sodium chlorate gave good results on convolvulus. In 1928 Aslander gave the results of an elaborate series of experiments on Californian thistle, and it was this article that induced the importation of chlorate into New Zealand, .the first consignments arriving early in 1929. Tho Department of Agriculture gave most attention to the effect of the treatment on ragwort, and Canterbury Agricultural College to its effect on Californian. thistle. The results were most striking. The Department reports that complete kills of soft weeds such as ragwort are secured, and Lincoln College has found that Californian thistle patches that have resisted every known method of treatment for 30 years and more are almost completely, exterminated in one season, the few remaining sickly plants being easily finished off in the second year. While the effect of the treatment is temporarily to bare the ground, clover and twitch, and any grass seeds j sown, soon cover the patch over again, and'the cost of treatment amounts to only one halfpenny per! squire yard. goine Actual Beeults. At Cornell 'a s'olid field;, of Californian thistle was divided intp 96 plots each, about 100 square yards in area, and these plots were treated at four different times of the year with three different poisons, a certain number of the plots of course feeixig left untreated. Taking only the essential figures froin. the table, and changing the months of year to the corresponding month in . our hemisphere, we find the following results. TABLE 1. Number of ShooU of Californian tfhistle per clot before and after treatment with Sodium ' Chlorate. Cornell, 1928.

This tablo shows that applications 'of about half an ounce per square yard j practically killed tho thistle, and that j the spring treatment was less effectivethen'the autumn' treatments. The fol- , lowing table from Idaho shows one of i the least successful trials recorded. ' TABLE «. Reaulta from Sodium' Chlorate on .Californian Thistle. Idaho, 192& Number af plots ■Weight of Number where eradication chlorate of plots "as .

, It is explained; however, that most of thpse trials were on irrigated land, and that most cases of failure occurred when the water,was near the surface. When the land i* excessively dry or wet the treatment is likeljr to be ineffective. . Since complete and immediate control seems very desirable and since preliminary experiments showed that the nell applications of less than one ounce to tho square yard f ere too light, "the plots laid down at Lincoln were treated at the rate pf 2oz per square yard, on approximately Marsh 14th. TABLE 8. PLOTS AT LINCOLN, N.Z., , 1829-30-31. Before Number of Plants. I Field. ■ Treatment.' Feb., 1980. Febij-'UttU < I a ' " .. ... 144 , '7 0. |2B •• 87-82 268 4 . Roadside 72 ~2 ,0 The few plants left were easily killed by autumn treatment. The four that escaped.in field 28 were found among the grass, and had obviously been missed in the earlier treatments. Effect on Subsequent Growth. The Cornell trials indicate that if: the chlorate is applied in autumn-' and, the land worked in spring and a crop of oats sown, practically 'a full crop 'ii assured. TABLE 4. YIELD OF OATS AFTER SODIUM CHLORATE APPLIED AT loz PER SQUARE YARD IN DIFERENT MONTHS AT CORNELL."

With the heavier - dressings recommended for New Zealand, it is likely, that more interference with the subsequent crop will be found and the-fol-lowing table shows the state of j the ground after the applications at Lincoln' quoted above, viz. 2oz per' square yard applied in.March'. TAWT/F 5 EFFECT AT LINCOLN COLLEGE OF SODIUM CHLORATE ON SUBSEQUENT CROP. Field Crop. Effest next February. , o " Grass Stock kept patch quite hare 28 r! Grass Stock kept patch quite bare 15 ' Potatoes Half a crop '• Roadside Glass Weeds, clovers and ches covered the land completely. Character of the Chlorate. Sodium chlorate is a white crystalline powder somewhat like common salt in appearance. It is made at Niagara Falls, and at several.European chemical works, sodium chlorate (common salt) being the basal material worked 0n..1t is not corrosive and not poisonous. It can be handled as freely as common salt, and has no'effeet on sheep or cattle grazing where ■ the weed-killer ,is spread. It is, however, reported .that ' poisonous weeds that .are usually re--1 jected by stock are sometimes, eaten > when wilted after being sprayed, so wheje £oxgJovs or hemlock or oth#r

poisonous .weeds aw betogf would be advisable to ,remoYes*tocac for, . a, few djtys. .It decomposes in„the-Boii v and disappears'in a most important character, as' succeeding..crop, ttKgrowafJfcer,, . thejweed-killer has, donHWwork,f.rphe*. ) decomposition takes, place '^orfi.TapMly*; when} tne soil • • tempejfofo*> is and "this & probably uttfeast; pa^t'«ar;*fche , explanation yfay on Calif ornian. tor, yie.aut'umnraiiia have wheit. the,*weed-killer'ifl k »pplie;tf t .in the, > heat of summer^., f," *,--,', <\ . [-, (~ v-.\ ,' The price of tlie^kiatd'riarin:,Christ' church 1 per ewt,' -If is'W,ftsed.afc*4sJw't pe*aore thi& means' of-ifctf pertierfy and it -is not suggested that'ike chlorate could.be whole 'fields of thigue,"- On small l .patches ;the ; expensejof lone - halfpenny' per square yard is quite/econoraicafc . , •• .- Fire Bisk. ■ lx '- ' When, with; other' '..substances such, as Bulphur or ch'arcoaVmost of the; chlorates are' explosive, and slowly coin- ' bustible material impregnated wjth Sodium chlorate burns rapidly. Thug, clothes saturated with sodium.chlorate' solution and' allowed to dry have more than in New Zealand been '.the, cause of painful burns., and clothes so' saturated be 'carefully and repeatedly rinsed before 'being used again. Any residues' of' sulphur left. in spray pumps about. to >be ! used for chlorates should: be carefully washed out, and chlorates should not be stored near dry, dusty combustible material such as charco'aL. '< Provided, reasonable, care- is taken, sodium is perfectly safe jto use, just as, with,' able care, 1 we' use with perfect safety' much more explosive commodities such as gunpowder, , , < • • ' Methods of Application. - "Trials by Humbert and others indicate that each kind of Speed" requires a specific .amount of. chlorate per square yard, and it does not matter,what .too strength of the solution,, is, or whether" the chlorate is f dissolved- in .water it all or applied dry, so long .as.sufficient quantities are applied/iiln some, cases it. may_ be. more convenient,' or.; mpre economical,* or evenness of spreading .to dwso , h»"'.th t e' powder, and ■• in' other. eaajjjs : . "these , .advantages may be more easily secured by applying the powder ik the' dry''state!,. With Californian thistly 'the^'dry.'applM cation seems u "% As indicated above, autumn", applica- , tioas. seem, mote satisfactory; thaa. those . j * . '"" i ,

, ,tion i^-monEf^psajti]^ bammed stdu^viiot taKould* not'-l^^^^iT^&^liia^pt^fflK Make. 1 coVer- to the,utmost limit of:she s fi|ta*<jfb«s£s • remaining sickly till •chlorate'again. ' 4 ] ?,'■.-{JVw, Convolvulu&-^Appiy'dr^l2o < zperjßquaffi( ' yard after nower&g;', Ktake'. Bpre."s~6]|t even distribution^, Store - >fhatt jpa% J jfi£ plication'is Long, twitch—Mow - before \ajjjplying ' weedkiller, i Apply, | in the early autumn and *gaia } square, yai;d when new gro^h.appejars. 1 Ragwort—Spray <jyhen*S ttia ■ '•fP'jbwij&J *. high In' October, m&fastSi Oj&t^i*!Bgsi * 'wetting is Teq'uiredL'Mak.e'.a'SblTition of J./a.to ,61b of chlorate'W-10 ' water. - " * .-.% f '^V ■ Other success I ed from spraying St, Boyal,,Oxeye Daisy-and ragwort. Spraying blackberry* Hs,m 43M pureljf^experimental, stage,; Mtltome partial successes tlVcdrded, £ Copies ~;of \this-, Ntained ,<from the ' secretary, Canterbury Chamber-1 of I*.Q:" Btos. H £B7 •Chrisschureh.v '" ''' <'"■>;.-

applied in o£i. per Shoots Shoots JDftte before next •ppliod. ■ Jan. 1 . • sq. yard. . under loz. treatment. 188 Feb. SO Jos. 1S7 0 about loz. 131 1. H»r. 1 . . uxder Jo:r.' ' , ' |0Z. ■■■■ ' 231 \ 141 77 * 0 About loz. 330 ■ 1 . Mtj 1 . . under loz. Jos.' 341 6t 74 , ' o ' »!>out loz. 114 ll>' Oct. X . . under ion. 186 71 Joz. 13 . 4 about loz. 103 22

Pel eq. yard. 14 12 loz. 2 lioz. 22 ' 5 . 17 ljca. 66 ■ . 39 27

■ Yield in . bushels per aox».' ■. Applied on Ploughed after , on treated on untreated soil. soil. Jon. 1 S months 3-2 32 Mch. 1 ... 6 months 37 , . 87 Hay 1 •• 4 months 28 aft Oct. 1 . . 1 week , 0 29