The carry-over of atrazine (2-chloro-4-ethylamino-6-isopropylamino-1 ,3,5-s-triazine), which occasionally causes damage to susceptible crops grown in rotation with atrazine-treated maize (Zea mays L.), calls for a refinement of the specified recropping intervals. Bioassays were conducted in a glasshouse to evaluate, w~h nine soils, the tolerance to atrazine shown by dry beans (Phaseolus vulgaris L. cv. Teebus), grain sorghum (Sorghum bicolor (L.) Moench cv. NK222), oats (Avena sativa L. cv. SWK001), soybeans (Glycine max (L.)Merr. cv. Forrest) and sunflower (Helianthus annuus L. cv. S0222). Significant differences between the tolerance of test species in experiments where dry beans/sunflower and oats/soybean combinations were evaluated are inconsistent with the single recrop interval that is stipulated for all four species. The amount of atrazine that was required to elicit a significant response from a particular test crop varied from soil to soil. The variable availability of atrazine in different soils for uptake by crop species needs to be considered to limit the risk when a sensitive follow-up crop is selected for a soil in which the amounts of toxic atrazine residues are known.Oordraging van atrasien (2-chloor-4-etielamino-6-isopropielamino-1 ,3,5-s-triasien), wat skade aan gevoelige opvolggewasse veroorsaak, vereis die verfyning van wagperiodes wat na gebruik van die onkruiddoder in mielies gestel word. Met biotoetse in 'n glashuis is die weerstandbiedendheid van droebone (Phaseolus vulgaris L. cv. Teebus), graansorghum (Sorghum bicolor (L.) Moench cv. NK222), hawer (Avena sativa L. cv. SWK001). sojabone (Glycine max (L.) Merr. cv. Forrest) en sonneblom (Helianthus annuus L. cv. S0222) teenoor atrasien in nege gronde vergelyk. Betekenisvolle verskille tussen die verdraagsaamheid van spesies in eksperimente waar die droeboon/sonneblom en hawer/sojaboon kombinasies getoets is, word nie deur die enkele wagperiode, wat vir al vier spesies aanbeveel word, weerspieel nie. Die hoeveelheid atrasien wat nodig was om 'n betekenisvolle reaksie by plante uit te 10k, het van grond tot grond verskil. Verskille tussen gronde, wat betref die beskikbaarheid van atrasien vir opname deur plante, behoort in ag geneem te word ten einde die risiko verbonde aan die keuse van 'n opvolggewas vir grond wat bekende hoeveeJhede toksiese atrasienresidue bevat so klein moontlik te hou.
