Effect of Biostimulants Added to Postemergence Herbicides in Corn , Oats and Winter Wheat

There is limited information available on the effect of biostimulants such as Crop Booster or RR SoyBooster on corn, oats and winter wheat under Ontario environmental conditions. A total of 37 field experiments were conducted in corn, oats and winter wheat at two locations (Ridgetown and Exeter, Ontario, Canada) to evaluate the effect of Crop Booster or RR SoyBooster on crop injury, weed control and yield. The addition of Crop Booster to glyphosate did not affect weed control or corn yield except at 4 weeks after herbicide application (WAA) when control of pigweed species was increased by 1% and at 4 and 8 WAA when control of common lambsquarters was reduced by 1%. The addition of RR SoyBooster to glyphosate did not affect crop injury, weed control or corn yield. The addition of Crop Booster to glyphosate + topramezone + atrazine did not affect crop injury, weed control or corn yield except at 4 WAA when control of common ragweed was reduced by 1%. The tank mix of Crop Booster with glyphosate + thiencarbazone-methyl did not affect crop injury, weed control or corn yield except at 4 WAA when control of green foxtail and annual grasses were reduced by 2% and 1%, respectively. The addition of Crop Booster to bromoxynil/ MCPA had no significant effect on crop injury, weed control or yield of oats or winter wheat.


Introduction
Wheat (Triticum aestivum L.), oats (Avena sativa L.) and corn (Zea mays L.) are three important field crops grown in Canada [1].Canada produces nearly 25,000,000 tonnes of wheat, 3,000,000 tonnes of oats and 11,000,000 tonnes of corn annually making it the 2 nd , 7 th and 11 th largest wheat, oats and corn producer in the world, respectively [1] [2].Intensive agronomic practices, including proper weed management and plant nutrition, are needed for profitable production of winter wheat, oats and corn.
Biostimulants have been marketed by agricultural products companies for enhancing crop growth and yield of various crops for a number of years.Biostimulants have been defined as compounds, substances and other products such as microorganisms, trace elements, enzymes, plant growth regulators that when applied in small quantities to plants or soils can enhance plant growth and development by increasing the efficiency of physiological process within plants [3] [4].Biostimulants have been reported to increase crop efficiency and enhance nutrient availability, water-holding capacity, increase antioxidants, enhance metabolism and increase chlorophyll production in plants [4]- [11].
According to the developers, Crop Booster compensates for plant's inability for nutrient uptake under stress from the soil by increasing foliar tissue nutrient concentration which enables plants to produce the enzymes and organic acid needed to combat stress [12].Crop Booster is also promoted by the Axter Agrosciences Inc. as a biostimulant that works synergistically with herbicides to decrease stresses that may be caused by the use of post emergence herbicides in crops [12].
Ontario producers need information on the effect of biostimulants such as Crop Booster or RR SoyBooster on crop growth and weed control to make informed decisions on their use in order to maximize farm profitability.The demand on growers to minimize per unit cost of production is increasing.In the absence of clear data on the effect of biostimulants such as Crop Booster or RR SoyBooster on crop injury, weed control and crop yield, Ontario growers and ag-retailers rely on their "best guess" when to use these products.This can result in the application of ineffective products which do not address crop growth or yield or weed problems and results low return on investment, reduced profitability and unnecessary loading of chemicals in the environment.Limited information exists on the effects of the co-application of Crop Booster or RR SoyBooster with commonly used herbicides in corn, oats and winter wheat under Ontario environmental conditions.
The objective of this study was to evaluate if there is any benefit of adding Crop Booster or RR SoyBooster to post emergence herbicides that are commonly used in corn, oats and winter wheat in Ontario.Field plots were 2 m wide and 8 or 10 m long.Corn was seeded at 80,000 seeds ha −1 in rows that were spaced 0.75 m apart at a depth of 4 cm in early to late May of each year.Oats were seeded with a double disc drill at 140 kg•ha −1 in rows spaced 17.5 cm apart at a depth of 4 cm in late April.Winter wheat was seeded with a double disc drill at 150 kg•ha −1 in rows spaced 17.5 cm apart at a depth of 4 cm in mid-September to late October.Herbicide treatments were applied with a CO 2 -pressurized back-pack sprayer equipped with Hypro ULD120-02 nozzle tips (Hypro, New Brighton, MN) calibrated to deliver 200 L•ha −1 of water at 200 kPa.Herbicide applications were made with a 1.5 m boom with four nozzles spaced 50 cm apart.

Materials and Methods
Estimate of crop injury was visually estimated on a scale of 0 (no injury) to 100% (complete plant death) at 1 and 4 weeks after herbicide application (WAA).Weed control was visually estimated on a scale of 0 (no control) to 100% (complete weed control) at 4 and 8 weeks after herbicide application (WAA).Crops were harvested from each plot with a small plot combine, weight and seed moisture content were recorded, and yields were adjusted to 15.5% seed moisture content for corn, 13.5% seed moisture content for oats and 14% seed moisture content for winter wheat.
Data were analyzed as an RCBD using PROC MIXED in SAS 9.2.Herbicide treatment was considered a fixed effect, while environment (year-location combinations), 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-test and random effects were tested using a Z-test of the variance estimate.The UNIVARIATE procedure was used to test data for normality and homogeneity of variance.The untreated check (for injury ratings) was excluded from the analysis.To satisfy the assumptions of the variance analyses, if needed, weed control ratings were arcsine square root transformed.Treatment comparisons were made using contrasts.Data compared on the transformed scale were converted back to the original scale for presentation of results.

Corn
There was no injury in corn with any of the herbicides evaluated (data not shown).The addition of Crop Booster or RR SoyBooster to glyphosate, glyphosate + topramezone + atrazine and glyphosate + thiencarbazone-mrthyl/ tembotrione had no effect on corn injury at rates evaluated (data not shown).
The addition of Crop Booster to glyphosate did not cause any effect on the control velvetleaf, pigweed species, common ragweed, common lambsquarters and annual grasses except at 4 WAA when control of pigweed species was increased by 1% and at 4 and 8 WAA when control of lambsquarters was reduced by 1% (Table 1).The addition of RR SoyBooster to glyphosate did not affect control of velvetleaf, pigweed species, common ragweed, common lambsquarters, green foxtail and annual grasses (Table 2).The addition of Crop Booster to glyphosate + topramezone + atrazine also did not affect control of velvetleaf, pigweed species, common ragweed, common lambsquarters, green foxtail and annual grasses in corn except at 4 WAA when control of common ragweed was reduced by 1% (Table 3).The addition of Crop Booster to glyphosate + thiencarbazonemethyl/tembotrione did not affect control of pigweed species, common ragweed, common lambsquarters, green foxtail and annual grasses in corn except at 4 WAA when control of green foxtail and annual grasses were reduced by 2% and 1%, respectively (Table 4).
The addition of Crop Booster or RR SoyBooster to corn increased yield as much as 2.5% with glyphosate and glyphosate + topramezone + atrazine and decreased yield as much as 1.5% with glyphosate + thiencarbazone/tembotrione but the differences were not statistically significant (Tables 1-4).Hanson [8] studying a biostimulant (Humates) found significant increases in yield of vegetable crops with biostimulants.Corn yields have been shown to increase significantly in other studies with other biostimulants [9].

Oats
There was minimal injury (1% or less) injury in oats with the herbicides evaluated alone or when co-applied with Crop Booster (data not shown).The addition of Crop Booster to bromoxynil/MCPA had no effect on oats injury at rates evaluated (data not shown).

Winter Wheat
There was minimal injury (1% or less) injury in winter wheat with herbicides evaluated alone or in tank mix combination with Crop Booster (data not shown).The addition of Crop Booster to bromoxynil/MCPA had no effect on winter wheat injury at rates evaluated (data not shown).
Bromoxynil/MCPA provided as much as 97% control of common ragweed and 99% control of common lambsquarters in winter wheat (Table 6).The addition of Crop Booster to bromoxynil/MCPA did not affect the control of common ragweed and common lambsquarters in winter wheat (Table 6).
Winter wheat yield ranged from 5.03 -5.16 MT ha −1 among treatments evaluated.The addition of Crop Booster to bromoxynil/MCPA increased winter wheat yield 2.6% however the difference was not statistically significant (Table 6).In other studies, Al-Majathoub [11] studying four different biostimulants (Vigro, Biomin, Humiplus and Humacare) found as much as 21% increase in tiller numbers and as much as 8.2% increase in wheat yield.

Conclusion
Based on these results, there was no increase in visible injury with the addition of Crop Booster to glyphosate, glyphosate + topramezone + atrazine and glyphosate + thiencarbazone-methyl/tembotrione in corn.The addition of Crop Booster to glyphosate, glyphosate + topramezone + atrazine and glyphosate + thiencarbazone/tembotrione had minimal effect (2% or less) on weed control.There was a small numeric increase in corn yield with the addition of Crop Booster or RR SoyBooster to glyphosate and Crop Booster to glyphosate + topramezone + atrazine, but this increase in yield was not statistically significant at the p = 0.05 level.Additionally, there was minimal visible injury (1% or less) with the addition of Crop Booster to bromoxynil/MCPA in oats and winter wheat.The addition of Crop Booster to bromoxynil/MCPA also did not affect weed control in oats and winter wheat.There was a small numeric increase in oat and winter wheat yield with the addition of Crop Booster to bromoxynil/MCPA, but this increase in yield was not statistically significant at the p = 0.05 level.

Table 1 .
Comparison of weed control 4 and 8 WAA, and yield for glyphosate alone vs glyphosate plus Crop Booster in Roundup Ready corn.Values for the weedy check were not included in the analysis a .

Table 2 .
Comparison of weed control 4 and 8 WAA, and yield for glyphosate alone vs glyphosate plus RR SoyBooster.Values for the weed-free check were not included in the contrasts a .aAbbreviations: ABUTH, velvetleaf; AMASS, green or redroot pigweed; AMBEL, common ragweed; CHEAL, common lambsquarters; GGGAN, annual grass; SETVI, green foxtail; WAA, weeks after herbicide application.b Significance of contrasts comparing glyphosate alone with glyphosate plus SoyBooster denoted by * for P < 0.10 and ** for P < 0.05 beside the means.

Table 3 .
Comparison of weed control 4 and 8 WAA, and yield for glyphosate + topramezone + atrazine alone vs glyphosate + topramezone + atrazine + Crop Booster in Roundup Ready corn.Values for the weedy check were not included in the analysis a .

Table 4 .
Comparison of weed control 4 and 8 WAA, and yield for glyphosate + thiencarbazone/tembotrione alone vs glyphosate + thiencarbazone/tembotrione + Crop Booster in Roundup Ready corn.Values for the weedy check were not included in the analysis a .

Table 5 .
Comparison of weed control 4 and 8 WAA, and yield for bromoxynil/MCPA alone vs bromoxynil/MCPA + Crop Booster in oats.Values for the weedy check were not included in the analysis a .

Table 6 .
Comparison of visual weed control 4 and 8 WAA, and yield for bromoxynil/MCPA alone vs bromoxynil/MCPA + Crop Booster in winter wheat.Values for the weedy check were not included in the analysis a .Significance of contrasts comparing bromoxynil/MCPA alone with bromoxynil/MCPA + Crop Booster denoted by * for P < 0.10 and ** for P < 0.05 beside the means.