NO-TILL CORN

Abstracts:

• Effect of reduced herbicide rates and cultivation for weed control in no-till corn. 2000. W. S. Curran, L. D. Hoffman, D. D. Lingenfelter, and E. L. Werner. Proc. NEWSS 54:34.

Effect of reduced herbicide rates and cultivation for weed control in no-till corn. 2000. W. S. Curran, L. D. Hoffman, D. D. Lingenfelter, and E. L. Werner. Proc. NEWSS 54:34.

An experiment was repeated for three growing seasons at the Agronomy Research Farm near Rock Springs, PA. The experiment was part of the NE-92 Regional Project and a similar study was conducted at Cornell University. The objective was to examine the effect of reduced herbicide rates and row cultivation for weed control in no-till corn for grain or silage. The corn for grain was no-till planted into shredded corn stalks, while the corn for silage was no-till planted into a rye (Secale cereale L.) cover crop. Approximately 5 days prior to corn planting, 1.0 lb ai/A glyphosate was broadcast applied to kill emerged vegetation including the rye cover crop. The rye cover crop at corn planting was 12 to 18 inches tall ranging from 1380 to 2470 lb/A dry matter, depending on the year. Five weed control treatments included a broadcast application of atrazine, metolachlor, and pendimethalin at 1.36 + 1.64 + 0.75 lb ai/A, respectively (1X), the 1X treatment followed by cultivation (1X+C), the 1X treatment applied at one-half the rate followed by cultivation (0.5X+C), the 1X treatment applied in a 15 in band followed by cultivation (B+C), and an untreated plot. Row cultivation was accomplished using a Sukup no-till cultivator. A single cultivation was performed about 5 weeks after corn planting in 1996, while two cultivation's approximately one week apart (5 and 6 weeks after planting) were conducted in 1997 and 1998. The experiment was replicated four times and the treatments were repeated in the same field location each year for three years. Weed control treatments were evaluated through visual estimates of percent control, weed density, and weed biomass. Corn silage or grain yield measurements were collected each fall.

The dominant weeds in the study included common lambsquarters (Chenopodium album L.), giant foxtail (Setaria faberi Herrm.), smooth pigweed (Amaranthus hybridus L.), velvetleaf (Abutilon theophrasti Medic), common ragweed (Ambrosia artemisiifolia L.), and yellow nutsedge (Cyperus esculentus L.). Common lambsquarters was the most severe species present. In 1996 and 1997, control of common lambsquarters was better in corn grain/corn residue than in corn silage/rye residue. Control of the other weeds was similar across corn and rye residue. The 1X+C treatment provided 90% or greater weed control all three years, while the other treatments generally provided greater than 80% control. In 1998, control was less in untreated corn residue compared to untreated rye residue. In addition, control was better in the 1X corn residue treatment compared to the 1X rye residue plot. It appeared that rye residue provided some weed control benefit in 1998 in the absence of herbicide, but may have reduced herbicide performance in the absence of cultivation. In addition, corn vigor was reduced in 1998 in the rye residue treatments compared to the corn residue treatments. With one exception, grain and silage yields were reduced in only the untreated plot, compared to the other weed control treatments. In 1997, silage yield was higher in two of three cultivation treatments than in the 1X treatment. These data suggest that reduced herbicide rates with cultivation can effectively manage weeds in conservation tillage systems. However, crop residue can also impact weed severity and herbicide performance.