Vegetation Management and Corn Growth and Yield in Untilled Mixed-Species Perennial Sod

Vegetation management is considered a major limiting factor in the production of no-till corn (Zea mays L.) in mixed species perennial sod. Timing and the degree of sod control may influence corn growth and yield under these conditions. Field research was conducted at Arlington, WI, from 1983 to 1985 to evaluate the control of alfalfa (Medicago sativa L.), dandelion (Taraxacum oficinale Weber in Wiggers), perennial grass [Smooth bromegrass (Bromus inermis Leyss) and orchardgrass (Dactylis glomerata L.)], and annual weeds in corn planted no-till into sod, and to evaluate the effects of sod control methods on corn development and yield. Herbicide treatments included fall-applied glyphosate [N-(phosphonomethyl) glycine], atrazine [6-chloro-N-ethyl-N′-(1-methylethyl)-l,3,5-triazine-2,4-diamine] plus paraquat (1,1′-dimethyl-4,4′-bipyridinium ion), dicamba (3,6-dichloro-2-methoxybenzoic acid), 2,4-D [diethanolamine salt of (2,4-dichlorophenoxy)acetic acid], and dicamba plus 2,4-D; early preplant atrazine; preplant dicamba, 2,4-D, and dicamba plus 2,4-D and preemergence glyphosate or paraquat applied simultaneously with atrazine or cyanazine {2-[[4-chloro-6-(ethylamino)-l,3,5-triazin-2-yl]amino]-2-methylpropanenitrile}. All fall, early preplant, and preplant applications were followed by atrazine or cyanazine plus paraquat applied preemergence. Treatments containing fall-applied glyphosate usually gave 85% or greater control of all sod species. Dicamba plus 2,4-D was effective for alfalfa and dandelion control, but did not control perennial grasses. Dicamba or 2,4-D alone was not as effective as the combination. Preplant and preemergence treatments were influenced by yearly conditions and did not give complete control of all sod species. Redroot pigweed (Amaranthus retroflexus L.) was the major annual weed species both years and was effectively controlled by atrazine applied preemergence. Fall herbicide application resulted in up to 4°C higher soil temperatures than spring treatments during the first 14 d after planting, resulting in more rapid corn emergence. Corn plant density 20 d after planting was as much as 20 000 plants ha⁻¹ greater following fall herbicide application than preemergence application. By 40 d after planting there was little difference in corn plant density. Herbicide treatments that resulted in higher soil temperatures and rapid emergence resulted in silk emergence 5 to 7 d earlier. Fall herbicide application, especially glyphosate and atrazine plus paraquat, resulted in the greatest corn grain yields. Reductions in grain yield were probably due to soil temperature depression, soil moisture depletion, and competition from uncontrolled sod. Vegetation management and corn growth and development in corn planted no-till into sod was influenced by herbicide, time of application, and environment. Split herbicide treatments were necessary for complete vegetation control. Results of this research indicate that with proper herbicide selection and application timing, corn can be produced without tillage in mixed-species perennial sod. Research supported by the College of Agric. and Life Sci., Univ. of Wisconsin-Madison, and HATCH Project 2865.