Influence of Herbicides and Tillage on Sweet Corn Double Cropped After Peas

Dinitroaniline herbicides are widely used for production of canning peas (Pisum sativum L.). These are residual herbicides and the effects of residues has been long recognized to be influenced by tillage. Careful evaluation of these compounds was thus needed before growers could consider growing sweet corn (Zea mays L.) following peas in a double cropping system. Peas were therefore established in a field study (Typic Argindoll finesilty, mixed mesic soil), using various dinitroaniline herbicides for weed control. After pea harvest, half the area was plowed and planted to sweet corn, and the remaining area was planted with a minimum tillage method to the same crop. Observations were made of weed growth and pea and sweet corn performance. The tillage and planting systems alone influenced both weeds and sweet corn. Giant foxtail (Seteria faberi Herrm.) and velvetleaf (Abutilon theophrasti Medic.) populations were 63 and 87% higher, respectively, in the sweet corn check plots planted with conventional tillage than when planted minimum till. Sweet com population and yield were 15.6 and 14.4% higher, respectively, with conventional tillage than with minimum tillage. The dinitroaniline herbicides had a significant impact on the sweet corn crop only when it was planted using the minimum till system. Dinitramine [N⁴,N⁴-diethyl-α,α,α-trifluoro-3,5-dinitrotoluene-2,4-diamine], fluchloralin [N-(2-chloro-ethyl)-2,6-dinitro-N-propyl-4-(trifluoro methyl)aniline], pendimethalin [N-(l-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine], trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine), and a combination of oryzalin [3,5-dinitro-N⁴, N⁴-dipropyl-sulfanilamide] plus trifluralin residues were effective in reducing giant foxtail and velvetleaf populations in sweet corn. Ethalfluralin [N-I-ethyl-N-(2-methyl-2-propenyl)-2,6-dinitro-4-(trifluoromethyl)benzenamine] was effective in controlling the velvetleaf population. Trifluralin residues caused the greatest carryover injury to sweet corn stands and the intensity of injury increased with higher application rates. Only fluchloralin, ethalfluralin, and trifluralin at 0.84, 0.84, and 0.42 kg/ha, respectively, did not cause sweet corn injury. The best sweet corn yields were obtained following treatments of dinitramine, ethalfluralin, and fluchloralin.