There is little information on effect of pendimethalin residues in the soil used for weed management in dry bean, on winter wheat seeded 3 to 4 months after application in Ontario. A total of four field experiments were conducted over a four-year period (2008-2011) in Ontario to evaluate the effect of pendimethalin residues on winter wheat injury and yield grown in rotation with dry bean. Pendimethalin, applied PPI in dry bean, at 1080 and 2160 g ai ha-1 caused 1% to 3% injury and 4% to 9% winter wheat injury evaluated 1 and 4 weeks after emergence (WAE) in the fall and on approximately the first of May, June and July of the following year. Pendimethalin applied PPI in the spring at 1X or 2X manufacturer’s recommended rate (1080 or 2160 g ai ha-1) in dry bean caused no adverse effect on the winter wheat height evaluated in July of the following year and no adverse effect on maturity at harvest. Pendimethalin applied PPI at 1080 g ai ha-1 in dry bean in the spring caused no adverse effect on winter wheat yield, but pendimethalin applied at 2160 g ai ha-1 rate caused a 4% reduction in yield of winter wheat. Based on this study, pendimethalin applied PPI at 2160 g ai ha-1 has potential to cause injury and yield reduction in winter wheat grown in rotation with dry bean under Ontario environmental conditions.
Dry bean (Phaseolus vulgaris L.), winter wheat (Triticumaestivum L.), corn (Zea mays L.) and soybean (Glycine max L.) are frequently grown in rotation in southwestern Ontario. Residual activity of herbicides should be considered when used in a diverse crop rotation. Dry bean, a short season crop that matures in 80 - 100 days, is an ideal crop to grow prior to seeding winter wheat [
Pendimethalin, a dinitroaniline herbicide, is a selective herbicide that controls annual grasses such as barnyardgrass (Echinochloacrusgalli (L.) Beauv.), fall panicum (Panicumdichotomiflorum Michx.), giant foxtail (Setariafaberii Herrm.), green foxtail (Setariaviridis (L.) Beauv.), yellow foxtail (Setariaglauca (L.) Beauv.), smooth crabgrass (Digitariaischaemum (Schreb) Muhl.) and large crabgrass (Digitariasanguinalis (L.) Scop). Pendimethalin also has activity on annual broadleaved weeds in Ontario such as redroot pigweed (Amaranthusretroflexus L.) and common lambsquarters (Chenopodium album L.) including acetolactate synthase and triazine-resistant biotypes [
Pendimethalin is currently registered in lima bean, snap bean and adzuki bean in Ontario. Pendimethalin is also being considered for registration in additional market classes of dry bean as earlier studies have shown that pendimethalin applied PPI or PRE at the proposed rate of 1080 g ai ha−1 has an adequate margin of crop safety for use in black, cranberry, kidney, and white bean under Ontario environmental conditions [
The objective of this study was to evaluate the effect of pendimethalin residues on winter wheat injury, height, maturity and yield seeded following dry bean under Ontario environmental conditions.
2. Materials and Methods
Four f ield experiments were established at the Huron Research Station, Exeter, Ontario in the autumn of 2008 to 2010, with winter wheat harvested in the summer of 2009 to 2011. The soil characteristics are listed in
Dry bean was established using conventional tillage and winter wheat was direct seeded (no-tillage) immediately after dry bean harvest in the autumn. Experiments were arranged in a completely randomized block design with four replications. Treatments included preplant applications of pendimethalin at 0, 1080 and 2160 g ai ha−1 applied preplant incorporated (PPI). The PPI application of pendimethalin was made to the soil surface one day before seeding dry bean and was immediately incorporated into the soil to a depth of 5 cm with two passes (in opposite directions) of an S-tine cultivator with rolling basket harrows. Plots were 3 m wide (4 rows spaced 0.75 m apart) and 10 m long. Dry bean was seeded to a depth of 5 cm in late May to early June. In late August to early September of each year after dry bean was harvested, the plots were then seeded with Pioneer “25R47”, a commonly grown soft, red winter wheat cultivar in Ontario, in rows spaced 18 cm apart. At all locations, winter wheat was seeded 3 cm deep using a double disk seeder at a rate of 170 kg∙ha−1.
Herbicide treatments were applied using a CO2-pressurized backpack sprayer calibrated to deliver 200 L∙ha−1 at 240 kPa. The boom was 2.5 m long with six ultra-low drift nozzles (ULD120-02, Hypro, New Brighton, MN) spaced 50 cm apart. Plots were maintained weed free by cultivation and hand hoeing as required to eliminate the confounding effect of weed interference.
Winter wheat injury was visually estimated on a scale of 0 (no injury) to 100% (complete plant death) at 1 and 4 weeks after crop emergence (WAE) and on approximately the first of May, June and July of the following
Location | Year | Sand (%) | Silt (%) | Clay (%) | OMa (%) | pH | CEC |
---|---|---|---|---|---|---|---|
Exeter | 2008 | 33 | 35 | 32 | 3.4 | 7.9 | 31 |
Exeter | 2009 | 38 | 41 | 21 | 3.7 | 7.8 | 31 |
Exeter | 2010 | 36 | 39 | 25 | 3.6 | 7.8 | 32 |
Exeter | 2010 | 35 | 43 | 22 | 3.8 | 7.7 | 28 |
aOM: Organic Matter.
growing season. Winter wheat height was measured for 10 plants per plot in mid-July and averaged. Winter wheat was harvested from each plot with a small plot combine and seed moisture content and weight were recorded. Winter wheat seed yields were adjusted to 14% moisture.
Data were analyzed using PROC MIXED in SAS 9.2. Herbicide treatment was considered a fixed effect, while environment, the interaction between environment and herbicide treatment, and replicate nested within environment were considered random effects. Significance of the fixed effect was tested using F-tests and random effects were tested using a Z-test of the variance estimate. Environments were combined for all variables. The UNIVARIATE procedure was used to test data for normality and homogeneity of variance. For all injury ratings, the untreated check (assigned a value of zero) was excluded from the analysis. However, all values were compared independently to zero to evaluate treatment differences with the untreated check. To satisfy the assumptions of the variance analyses, injury 1 and 4 WAE, on approximately the first of May and June were square root transformed; winter wheat seed moisture content at harvest was log transformed. Treatment comparisons were made using Fisher’s Protected LSD at a level of P < 0.05. Data analyzed on the transformed scale were converted back to the original scale for presentation of results.
Statistical analysis indicated that environment by treatment interaction was not significant therefore, four data- sets were analyzed together. Crop injury symptoms from pendimethalin included slightly reduced growth with a slight purplish hue.
Pendimethalin applied PPI at 1080 g ai ha−1 in dry bean in the spring caused 1% to 3% visual injury in winter wheat evaluated 1 and 4 WAE in the fall and on approximately the first of May, June and July of the following year (
Pendimethalin applied PPI in the spring at 1X or 2X manufacturer’s recommended rate (1080 or 2160 g ai ha−1) in dry bean caused no adverse effect on the winter wheat height evaluated in July of the following growing season (
Pendimethalin applied PPI at 1080 g ai ha−1 in dry bean in the spring caused no adverse effect on winter wheat
Injury | |||||||||
---|---|---|---|---|---|---|---|---|---|
Treatment | Rate | 1 WAE | 4 WAE | May | June | July | Height | Moisture | Yield |
g ai ha−1 | % | cm | % | MT ha−1 | |||||
Untreated | 0 | 0 a | 0 a | 0 a | 0 a | 0 | 88 | 14.8 | 6.90 a |
Pendimethalin | 1080 | 1 a | 3 ab | 2 b | 1 ab | 2 | 87 | 14.8 | 6.86 ab |
Pendimethalin | 2160 | 4 a | 9 b | 6 b | 4 b | 5 | 86 | 15.0 | 6.65 b |
SE | 1 | 2 | 1 | 1 | 1 | 1 | 0.5 | 0.07 |
aWAE: Weeks after Wheat Emergence; PPI: Preplant Incorportated.
*Corresponding author.
Based on this study, Pendimethalin applied PPI at 1080 g ai ha−1 in dry bean in the spring causes minimal injury in winter wheat evaluated 1 and 4 WAE in the fall and on approximately the first of May, June and July of the following year. In addition, there was no effect on winter wheat height, maturity (seed moisture content) and yield. However, pendimethalin applied PPI at 2160 g ai ha−1 in dry bean in the spring causes significant injury in winter wheat evaluated 1 and 4 WAE in the fall and on approximately the first of May, June and July of the following year and can reduce yield as much as 4%. Based on these results there is the potential for winter wheat injury and yield loss in areas where there is spray overlaps of pendimethalin at the manufacturer’s rate of 1080 g ai ha−1.
The authors would like to acknowledge Todd Cowan for his expertise and technical assistance in these studies. Funding for this project was provided in part by the Grain Farmers of Ontario (GFO) and the GF2 program of the Agricultural Adaptation Council.