Vol. 51—1997 - NorthEastern Weed Science Society

63
DETECTION ND MOVEMENT PATTERN OF IMAZETHAPYR IN SELECTED
SOILS OF NEW JERSEY
S.W. Jourdan, B.A. Majek and A.O. Ayeni'"
ABSTRACT
Imaze apyr is among the most widely used herbicides for PRE and POST weed
control in legum s in world agriculture. Reports from North America have shown that the
herbicide has c over problems which in some instances have injured susceptible follow
crops in conven onal crop rotations. Studies have also shown that several factors influence
the soil persiste e behavior of imazethapyr. It is important to understand clearly under what
conditions are th carryover problems most likely to occur so the farmer can take this into
account in his c p rotation plans.
Betw n 1991 and 1995, laboratory and greenhouse studies at the Rutgers
Agricultural Re ch and Extension Center, showed that the degree of sugar beets root
length suppressi n caused by imazethapyr applied at 2.5 ppb to Berryland sand (97% sand,
1.5% organic m tter [OM)), increased as soil pH increased from 3.75 to 7.48. Among four
soils (pH adjust to 6.5) compared, the lowest concentrations of imazethapyr detectable with
sugar beets root ength were 0.5 ppb in acid washed sand (90% sand, 0.04% OM); 1.0 ppb
in Berryland san and Aura loamy sand (82% sand, 0.93% OM); and 5 to 10 ppb in Muck
soil (72% sand, 6.48% OM). In Berryland sand (pH 6.5), with normal watering and using
sugar beets root ength as imazethapyr indicator, the residue of imazethapyr applied to soil
columns at 0.07 kg ai/ha, remained in the 0 to 15 em soil layer for three months after
application. T e herbicide moved further down to 30-cm depth by the fifth month after
application, but esidue level dropped significantly in the 0 to 5 em soil layer. Under low
pH (5.5) and ro m temperature (26.7 "C), low level of imazethapyr residue was detected at 5
to 10 cm soilla er only when the soil moisture level was moderately high (approx. 70% field
capacity [FC]). Under neutral pH (7.0) and low temperature (10 °C), the dissipation of
imazethapyr wa slow with high residue level detected in the 0 to 10 and 0 to 15 cm soil
layers under 10 (approx. 50% FC) and moderately high soil moisture respectively, three
months after he icide application (MAHA). Under neutral pH and room temperature,
imazethapyr dis ipated rapidly, with low residue level detected in the 0 to 30 em soil layer
under low soil oisture, and very low level detected in the 5 to 30 cm soil layer under
moderaletly hi soil moisture. Imazethapyr residue was not detected beyond 3Q-cm soil
depth in any of e treatments 3 MAHA.
These dies showed that the bioavailability of imazethapyr is significantly enhanced
under high soil H (2. 6.5) and as low as 0.5 to 1.0 ppb is detectable in sand and loamy
sand soils using sugar beets root length as imazethapyr indicator. It was also demonstrated
that residue fro imazethapyr applied at 0.07 kg ai/ha, does not move beyond 30 em in the
soil profile up t five months after application; and carryover problem may be most serious
in low pH soil limed under low temperature and low moisture conditions.
'Former P stdoctoral Research Associate, Prof., Visiting Scientist, Rutgers Agricultural
Research and E tension Center, Rutgers University, Bridgeton, NJ 08302.