Translocation of aged cyclodiene insecticide residues from soil into forage crops and pastures at various growth stages under field conditions

Abstract

Field trials were conducted to measure translocation of pesticides by summer and winter forage/pasture species from soil containing aged residues of heptachlor and, to a lesser extent, dieldrin. Substantial amounts of heptachlor epoxide, and lesser amounts of gamma-chlordane were translocated to plants from contaminated soil. Residue levels varied with crop species and stage of plant development. In summer crops residues were higher in soybean > cowpeas > lab-lab > Sorghum > millet > sweet saccaline at the grazing and mature stages. Compared to glasshouse studies undertaken previously, residues in crops grown under field conditions were much lower. This apparently reflects the lower soil moisture levels and the reduced rates of translocation. Heptachlor residues in winter crops were highest in Saia oats > Berseem clover > Haifa clover > Cassia oats > Tetila ryegrass > Schooner barley > Shaftal clover > Hunter river lucerne at the grazing stage. There were no detectable levels in barley and oats at the mature stage. No dieldrin residues were translocated into the various crop species.