Influence of Soil pH ons-Triazine Availability to Plants

Field studies indicated that liming an acid Bladen silt loam from pH 5.5 to 7.5 increased the phytotoxicity of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)- s -triazine] and prometryn [2,4-bis-(isopropylamino)-6-methyoxy- s -triazine]. Liming greatly increased the persistence of atrazine, but did not affect prometryn dissipation. Liming increased the 14 C-concentration present in the shoots of corn ( Zea Mays L. ‘Pioneer 3369A’), cotton ( Gossypium hirsutum L. ‘Coker 201’), and soybeans [ Glycine Max (L.) Merr. ‘Ransom’] from soil treated with 14 C-ring labeled atrazine, prometryn, and hydroxyatrazine [2-hydroxy-4-(ethylamino)-6-(isopropylamino)- s -triazine] in greenhouse studies. Decreases in 14 C-uptake by the crops were associated with adsorption and degradation of the compounds in the soil. Atrazine was taken up in much greater amounts than hydroxyatrazine. Cotton absorbed less of the s -triazines than soybeans or corn from soil.