Soil Factor Effects on Tolerance of Two Corn (Zea mays) Hybrids to Isoxaflutole Plus Flufenacet1

摘要

Field experiments were conducted at three locations in 2000 and 2001 to evaluate what effect soil characteristics have on sensitivity of two corn hybrids to soil-applied isoxaflutole plus flufenacet. Soil types were a Flanagan silt loam with 3.9% organic matter (OM), a Drummer silty clay loam with 5.0% OM, and a Cisne silt loam with 2.1% OM. Soil pH was adjusted to four target levels, 7.0, at each location. Isoxaflutole plus flufenacet treatments consisted of the recommended rate (1×) and two times (2×), and four times (4×) the recommended rates based on soil type. Additional treatments included 1× and 2× isoxaflutole plus flufenacet with 1.1 kg/ha atrazine and S-metolachor plus atrazine as a control treatment. Corn hybrid ‘Garst 8366’ (G8366) was more sensitive to soil-applied isoxaflutole plus flufenacet compared with ‘Garst 8600’ (G8600). Corn injury occurred only at two of three locations. Addition of atrazine to the 1× and 2× isoxaflutole plus flufenacet treatments showed a trend (P = 0.15) toward increased injury and reduced yield only for the G8366 on the Cisne soil. The 4× rate of the premixture reduced yield 9 to 49% at two locations. Yields were reduced at the low-OM (2.1%) location, regardless of hybrid or application rate. At two locations, there was a negative linear relationship between soil pH and corn grain yield, particularly at the 4× rate. Corn visual injury and yield reductions were greatest from herbicide applications to low-OM soils with high pH levels.