Vol. 15—1961 - NorthEastern Weed Science Society

Sheets (1959) studied, under laboratory conditions the influence of soU
type on the activity of CDEC. He v~particule.rly concerned with organic and
cl~ content, ca.tion exchange caPaCity and pH. There was no clear cut influence
of e;ny of these characteristic$ on t:Q,ee.ctivity of CIBCas measured by
toxicity to oats. Using rates of CDECroughly ten fold that of field applications,
he found that with warm, moist conditions all levels of CDECwere
rendered relatively innocuous within three months.
U6f
Gantz and Slife (1960) confirmed the findings Otten (1957) regarding
the relative-lack of If!aCh1ng of CDiC with rainfa,ll. ',Tbese'WOrkers studied
the persistence of CDECunder 1!1Oistand dry soU conditions at. temperatures of
40 0, 60° .. Boo"and 100°F. They found little loss of activity under either
moist or dry soU conditions with the 40° and 6o°tres:tments. Initial
activity was the same for wet and dry soUs, regardless 01' temperature. There
was no difference in the activity of CDECin the mollitor dry soils at the
higher temperatures. except in t,he first· ;t'Wt),weelts. At this time" a much
higher level 01',act1vi'tywas ,noted under' 1!lOist,condit:l.ons. 'These findings are
at variance with those ofO'tten (1957)wbo found practicaJJ.y cOIIJPlete loss of
CDECac'tivi'tyat 82°F in about five d~ in moist soU.
M:lnsanto (1959) reports that vola'tUi ty may be an important factor. in- .
f'luencing activi'sy of CDEC. Vapor pressure of' CDECis stated 'to be 2.2 x 10- 3
mmof lfg a't 20°C. Water bas a V.P. of 17 mmof Hg at 20°C. l't was cal'culated
tha.t'1n; the absence .of' other forces such as physical or chemical adsorbtion,
CDECwould, evapera'te in less 'than eight hours at tempera'tures as low as '45°F.
An ex:per~ was also rePOrted in which CDEC,and CDAAvereapplied to dry
soU, surfaces and some treatments were covered with l/~ of 80il 1DlmediatSly
after treating. This soU coveriDg grea'tly increased Randox activity. Only
a't very low rates, one pound or less, could a. similar trend be noted for .
CDiC. PecUliarly" 'When,samples were watered 1DImediately after "treating, Which,
presumably, drsstically re4uced volatUity opPOrtunity, the same general beneficial
results :eromcovering CDAAwere noted. This. is highly suggestive that
factors otker ..than stra1gbt 'YolatUity mus't be involVed. Since ,'the vapor
pressures of CDAAana..,.cDECare of'the same order of magnitude (when actiVit,­
is considered atter a, period of' •a week) it was tabe. expected that the performance
of' both herbicides would be about the same. .However, CDECwas
distinc'tly less influenced by the shallow soil covering than was CDAA. T~:J.s
also suggests that volatility' per se is a qUestionable factor· influencing
CDEe,activity.
Havis (1959) reported that eight pounds of CDECSP,Plied tea dry soil
surfa.ce and then either incorpora.'ted by stirring with a sballow cultivator or
applYing one inch of' wa1ier gave very good weed coIrtroJ:. Applying CDECto a
we1i soU was 1$8.8 sa.'t1sfactory.. ~1ITing the wet soU decreased the aC'tivity.
No suggestion was made as totbe~ possible reasons for CDECvariab1e performance
dependent on. soU moisture CoD,diti.ons or mechanical incorporation.
Sweet (1960) reported that incorJ;lOration of CDECenhanced weed control
and ~a.'tly· increased damage to red beets •. ' He also showed 'that damage to
seeded crops under .fjAld And gt"epnho\un~ ~ondi+'iOl'lI'l COfl1d be l"8Mily correlated
59.