INHIBITION OF DINITROANILINE HERBICIDE ACTION BY PLANT LIPIDS, AND THE ROLE OF DINITROANILINE HERBICIDES IN THE PRODUCTION OF CROPS UNDER DOUBLE CROPPING SYSTEM

The effects of seed and root lipids on the susceptibility of plants to two substituted dinitroaniline herbicides were studied. Variability in lipid composition was observed in seeds of different plant species as well as cultivars within the same species. Susceptibility of plants to trifluralin and oryzalin decreased with an increase in percentage of total lipid in dry seeds. There was also a significant correlation between root lipid content and sensitivity to trifluralin and oryzalin. Seedlings grown from seeds with high lipid levels were observed to accumulate higher percentages of lipids in their roots and these roots were less susceptible than roots with lower lipid levels. Plant roots differed extensively in fatty acids composition but no single fatty acid appeared to uniquely influence trifluralin or oryzalin action. Treatment with trifluralin or oryzalin did not significantly alter the total lipid percentage or fatty acid compositions of roots.;The influence of seven dinitroaniline herbicides and tillage methods on the production of canning peas (Pisum sativum L.) and sweet corn (Zea mays L.) in a double cropping system was examined under field conditions. Visual observations of pea stand reduction as well as reduced shelled pea yields indicated that ethalfluralin at 0.84 kg/ha and trifluralin at rates in excess of 0.56 kg/ha were injurious to peas. The tillage and planting systems greatly influenced the sweet corn crop. The population of giant foxtail (Setaria faberi Herrm.) and velvetleaf (Abutilon theophrasti Medic.) in sweet corn were 63% and 87% higher, respectively, in areas planted with conventional tillage methods than in the no-till area. The sweet corn population and yield were 15.6% and 14.4% higher, respectively, following conventional tillage than no-tillage. The dinitroaniline herbicide residues resulting from pea treatment only affected the sweet corn when it was planted using the no-till system. Dinitramine, fluchloralin and ethalfluralin were most effective in controlling giant foxtail and velvetleaf in sweet corn and in increasing sweet corn yields.;The role of trifluralin in weed control for double-crop corn, sorghum (Sorghum bicolor L.), and soybeans (Glycine max (L.) Merr.) planted without tillage following canning peas was also studied under field conditions. Trifluralin residues resulting from the pea herbicide treatment reduced weed growth by 52% in corn, 52% in sorghum and 62% in soybeans, respectively, and increased grain yields of corn and soybeans by 10% and 28%, respectively, compared with the check. Trifluralin residues reduced sorghum stands by 44% and decreased grain yield by 17%. Trifluralin residues interacted with additional herbicide combinations applied to corn, sorghum or soybeans resulting in a better weed control than similar treatments without trifluralin residues. Soybeans were the most successful of the three secondary crops planted with no-tillage methods for grain. Grain yields of both no-till double cropped corn and sorghum were low.