Nine field trials (4 in corn and 5 in soybean) were conducted over 2 years (2014 and 2015) to determine if there is greater benefit of adding ammonium sulfate (AMS) (2.5 L·ha ˉ1 ) or an equal dollar value of glyphosate (406 g·ae·ha ˉ1 ) to glyphosate applied at 450, 675 or 900 g·ae·ha ˉ1 for weed control in corn and soybean. Glyphosate applied at 450 g·ae·ha ˉ1 controlled velvetleaf 90% to 98%, common ragweed 80% - 97%, common lambsquarters 91% - 99%, Eastern black nightshade 83% - 100% and barnyardgrass 73% - 97% in corn and common ragweed 37% - 89%, common lambsquarters 39% - 98%, barnyardgrass 90% - 98% and green foxtail 91% - 98% in soybean. The addition of AMS to glyphosate applied at 450, 675 or 900 g·ae·ha ˉ1 provided little to no added benefit for the control of velvetleaf, common ragweed, common lambsquarters, Eastern black nightshade, barnyardgrass and green foxtail in corn and soybean. There was a greater benefit in weed control efficacy by simply adding and equal dollar value of glyphosate (406 g·ae·ha ˉ1 ) than AMS (2.5 L·ha ˉ1 ) to glyphosate. There was no difference in corn or soybean yield among the herbicide treatments evaluated. Based on these results, addition of AMS to glyphosate at rates evaluated had little benefit on weed control efficacy or yield of corn and soybean.
The Ontario corn and soybean industry covers about 2,000,000 ha, and has annual farm-gate value of approximately $3.3 billion [
Currently, more than 90% of the corn and 79% of soybean produced in Ontario are seeded to glyphosate-resistant hybrids/cultivars [
Limited information exists on the effect of ammonium sulfate added to glyphosate in corn and soybean under Ontario environmental conditions which can lead to unnecessary expenditures.
The objectives of this research were to determine the benefit of adding ammonium sulfate or an equal dollar value of glyphosate (406 g∙ae∙ha−1) to glyphosate applied at 450, 675 or 900 g∙ae∙ha-1 for weed control in corn and soybean.
Four field trials (1 at Harrow in 2014 and 3 at Ridgetown in 2015) in corn and 5 field trials in soybean (1 at Harrow in 2014, 1 at Exeter in 2014 and 3 at Ridgetown in 2015) were conducted at the Agriculture and Agri-Food Canada Research Station, Harrow, Ontario, Huron Research Station, Exeter, Ontario and University of Guelph, Ridgetown Campus, Ridgetown, Ontario. The soil ranged from sandy loam to clay loam with 30% to 83% sand, 5% to 36% silt, and 13% to 33% clay, with 2.6% to 5.6% organic matter content and pH 6.0 to 7.4. Seedbed preparation included fall mouldboard plowing followed by two passes with a field cultivator with rolling basket harrows in the spring.
Studies were established as a randomized complete block design with four replications. Treatments for corn and soybean trials were the same and are listed in Tables 1-9. Weed-free control was maintained weed-free by hand hoeing as needed. Each plot was 3 m wide and 8 or 10 m long and consisted of four rows of glyphosate resistant corn/soybean spaced 0.75 m apart. Corn was planted at a rate of approximately 75,000 seeds∙ha−1 in May of each year. Soybean was planted at a rate of approximately 370,000 seeds∙ha−1 in May to early June of each year.
Herbicide treatments were applied using a CO2-pressurized backpack sprayer calibrated to deliver 200 L∙ha−1 aqueous solution at 240 kPa. The boom was 1.5 m wide with four ULD120-02 nozzles (Hypro, New Brighton , MN , USA ) spaced 0.5 m apart. The herbicides were applied postemergence when weeds were approximately 10 cm in height which corresponded to the V2-4 stage for corn and V2-3 stage for soybean.
Weed control was visually estimated on a scale of 0 (no control) to 100% (complete control) at 1, 2, 3, 4 and 8 weeks after herbicide application (WAT). Weed density (soybean only) and dry weight (soybean only) by species were evaluated 4 WAT by counting and cutting plants at the soil surface form 1 square meter in each plot. Plants were dried at 60 C to constant moisture and then weighed. Corn or soybean was harvested at maturity with a small plot combine, weight and moisture recorded and yields were adjusted to 15.5% and 13% seed moisture content for corn and soybean, respectively.
Data were analyzed using PROC GLIMMIX in Statistical Analysis Systems Software
Control | ||||||
---|---|---|---|---|---|---|
Treatment | Rate | 1 WAT | 2 WAT | 3 WAT | 4 WAT | 8 WAT |
g∙ae∙ha−1 | % | |||||
Weedy check | 0 | 0 | 0 | 0 | 0 | |
Weed-free check | 100 a | 100 a | 100 | 100 | 100 | |
Glyphosate | 450 | 90 d | 97 c | 98 | 98 | 98 |
Glyphosate + AMS | 450 + 2.5 L∙ha−1 | 93 cd | 98 bc | 99 | 98 | 98 |
Glyphosate | 956 | 97 bcd | 99 ab | 99 | 100 | 100 |
Glyphosate | 675 | 96 bcd | 99 bc | 99 | 98 | 99 |
Glyphosate + AMS | 675 + 2.5 L∙ha−1 | 98 abc | 99 ab | 99 | 98 | 98 |
Glyphosate | 1181 | 99 ab | 100 a | 99 | 100 | 100 |
Glyphosate | 900 | 98 abc | 100 a | 99 | 100 | 100 |
Glyphosate + AMS | 900 + 2.5 L∙ha−1 | 99 ab | 100 a | 99 | 98 | 98 |
Glyphosate | 1406 | 99 ab | 100 a | 99 | 99 | 99 |
aAbbreviations: AMS, ammonium sulfate; WAT, weeks after herbicide application. Means followed by the same letter within a column are not significantly different according to Fisher’s Protected LSD at P < 0.05.
Control | ||||||
---|---|---|---|---|---|---|
Treatment | Rate | 1 WAT | 2 WAT | 3 WAT | 4 WAT | 8 WAT |
g∙ae∙ha−1 | % | |||||
Weedy check | 0 | 0 | 0 | 0 | 0 | |
Weed-free check | 100 a | 100 | 100 a | 100 a | 100 a | |
Glyphosate | 450 | 95 c | 97 | 94 c | 80 b | 85 b |
Glyphosate + AMS | 450 + 2.5 L∙ha−1 | 96 c | 92 | 94 c | 81 b | 85 b |
Glyphosate | 956 | 98 b | 98 | 97 b | 84 b | 91 b |
Glyphosate | 675 | 99 ab | 98 | 97 b | 85 b | 89 b |
Glyphosate + AMS | 675 + 2.5 L∙ha−1 | 98 b | 97 | 96 bc | 86 b | 90 b |
Glyphosate | 1181 | 99 ab | 99 | 97 b | 89 b | 93 b |
Glyphosate | 900 | 99 ab | 99 | 99 ab | 86 b | 92 b |
Glyphosate + AMS | 900 + 2.5 L∙ha−1 | 99 ab | 99 | 97 b | 87 b | 93 b |
Glyphosate | 1406 | 99 ab | 99 | 98 ab | 89 b | 93 b |
aAbbreviations: AMS, ammonium sulfate; WAT, weeks after herbicide application. Means followed by the same letter within a column are not significantly different according to Fisher’s Protected LSD at P < 0.05.
Control | ||||||
---|---|---|---|---|---|---|
Treatment | Rate | 1 WAT | 2 WAT | 3 WAT | 4 WAT | 8 WAT |
g∙ae∙ha−1 | % | |||||
Weedy check | 0 | 0 | 0 | 0 | 0 | |
Weed-free check | 100 | 100 a | 100 a | 100 | 100 | |
Glyphosate | 450 | 99 | 99 b | 98 b | 91 | 94 |
Glyphosate + AMS | 450 + 2.5 L∙ha−1 | 99 | 99 b | 98 b | 91 | 94 |
Glyphosate | 956 | 100 | 99 b | 98 b | 93 | 95 |
Glyphosate | 675 | 100 | 99 b | 99 b | 93 | 94 |
Glyphosate + AMS | 675 + 2.5 L∙ha−1 | 99 | 99 b | 99 b | 94 | 96 |
Glyphosate | 1181 | 100 | 99 b | 99 b | 95 | 96 |
Glyphosate | 900 | 100 | 100 a | 99 b | 94 | 96 |
Glyphosate + AMS | 900 + 2.5 L∙ha−1 | 100 | 100 a | 99 b | 94 | 96 |
Glyphosate | 1406 | 100 | 100 a | 99 b | 95 | 97 |
aAbbreviations: AMS, ammonium sulfate; WAT, weeks after herbicide application. Means followed by the same letter within a column are not significantly different according to Fisher’s Protected LSD at P < 0.05.
Control | ||||||
---|---|---|---|---|---|---|
Treatment | Rate | 1 WAT | 2 WAT | 3 WAT | 4 WAT | 8 WAT |
g∙ae∙ha−1 | % | |||||
Weedy check | 0 | 0 | 0 | 0 | 0 | |
Weed-free check | 100 | 100 | 100 | 100 | 100 | |
Glyphosate | 450 | 100 | 100 | 99 | 85 | 83 |
Glyphosate + AMS | 450 + 2.5 L∙ha−1 | 100 | 100 | 99 | 83 | 81 |
Glyphosate | 956 | 100 | 100 | 99 | 88 | 83 |
Glyphosate | 675 | 100 | 100 | 99 | 88 | 82 |
Glyphosate + AMS | 675 + 2.5 L∙ha−1 | 100 | 100 | 99 | 88 | 84 |
Glyphosate | 1181 | 100 | 100 | 99 | 92 | 88 |
Glyphosate | 900 | 100 | 100 | 99 | 89 | 83 |
Glyphosate + AMS | 900 + 2.5 L∙ha−1 | 100 | 100 | 99 | 89 | 85 |
Glyphosate | 1406 | 100 | 100 | 100 | 90 | 88 |
aAbbreviations: AMS, ammonium sulfate; WAT, weeks after herbicide application. Means followed by the same letter within a column are not significantly different according to Fisher’s Protected LSD at P < 0.05.
Control | |||||||
---|---|---|---|---|---|---|---|
Treatment | Rate | 1 WAT | 2 WAT | 3 WAT | 4 WAT | 8 WAT | Yield |
g∙ae∙ha−1 | % | T/ha | |||||
Weedy check | 0 | 0 | 0 | 0 | 0 | 10.62 b | |
Weed-free check | 100 a | 100 | 100 | 100 a | 100 a | 14.64 a | |
Glyphosate | 450 | 97 b | 97 | 97 | 73 b | 85 b | 13.87 a |
Glyphosate + AMS | 450 + 2.5 L∙ha−1 | 97 b | 98 | 98 | 70 b | 76 b | 13.98 a |
Glyphosate | 956 | 100 a | 100 | 98 | 77 b | 86 b | 14.06 a |
Glyphosate | 675 | 99 ab | 99 | 99 | 75 b | 84 b | 13.82 a |
Glyphosate + AMS | 675 + 2.5 L∙ha−1 | 98 b | 99 | 98 | 79 b | 79 b | 13.99 a |
Glyphosate | 1181 | 100 a | 99 | 98 | 81 b | 85 b | 14.15 a |
Glyphosate | 900 | 100 a | 99 | 99 | 80 b | 89 b | 14.06 a |
Glyphosate + AMS | 900 + 2.5 L∙ha−1 | 100 a | 100 | 99 | 82 b | 90 b | 14.19 a |
Glyphosate | 1406 | 100 a | 100 | 99 | 82 b | 83 b | 14.07 a |
aAbbreviations: AMS, ammonium sulfate; WAT, weeks after herbicide application. Means followed by the same letter within a column are not significantly different according to Fisher’s Protected LSD at P < 0.05.
Control | ||||||||
---|---|---|---|---|---|---|---|---|
Treatment | Rate | 1 WAT | 2 WAT | 3 WAT | 4 WAT | 8 WAT | Density | Dry weight |
g∙ae∙ha−1 | % | #/m2 | g/m2 | |||||
Weedy check | 0 | 0 | 0 | 0 | 0 | 4.7 c | 11.1 b | |
Weed-free check | 100 a | 100 a | 100 a | 100 a | 100 a | 0 | 0 | |
Glyphosate | 450 | 37 d | 68 f | 84 e | 88 e | 89 d | 2.0 b | 0.9 a |
Glyphosate + AMS | 450 + 2.5 L∙ha−1 | 42 d | 74 ef | 88 de | 91 de | 93 c | 1.5 ab | 0.8 a |
Glyphosate | 956 | 60 bc | 86 bcd | 93 bcd | 96 bcd | 97 b | 1.4 ab | 0.5 a |
Glyphosate | 675 | 58 c | 79 de | 91 cd | 93 cd | 92 cd | 1.8 b | 0.9 a |
Glyphosate + AMS | 675 + 2.5 L∙ha−1 | 67 bc | 84 cd | 92 bcd | 95 bcd | 96 bc | 0.9 ab | 0.3 a |
Glyphosate | 1181 | 68 bc | 94 ab | 96 bc | 98 b | 98 b | 0.6 a | 0.2 a |
Glyphosate | 900 | 65 bc | 90 bc | 95 bc | 96 bc | 97 b | 0.6 a | 0.3 a |
Glyphosate + AMS | 900 + 2.5 L∙ha−1 | 71 bc | 90 bc | 96 bc | 97 bc | 98 b | 0.9 ab | 0.3 a |
Glyphosate | 1406 | 73 b | 95 ab | 97 b | 98 b | 98 b | 0.7 a | 0.1 a |
aAbbreviations: AMS, ammonium sulfate; WAT, weeks after herbicide application. Means followed by the same letter within a column are not significantly different according to Fisher’s Protected LSD at P < 0.05.
Control | ||||||||
---|---|---|---|---|---|---|---|---|
Treatment | Rate | 1 WAT | 2 WAT | 3 WAT | 4 WAT | 8 WAT | Density | Dry weight |
g∙ae∙ha−1 | % | #/m2 | g/m2 | |||||
Weedy check | 0 | 0 | 0 | 0 | 0 | 25.0 c | 9.1 b | |
Weed-free check | 100 a | 100 | 100 a | 100 a | 100 a | 0 | 0.0 | |
Glyphosate | 450 | 39 d | 87 | 96 c | 98 b | 98 b | 3.5 ab | 0.4 a |
Glyphosate + AMS | 450 + 2.5 L∙ha−1 | 46 cd | 91 | 98 bc | 99 ab | 98 b | 3.5 ab | 0.5 a |
Glyphosate | 956 | 62 bc | 96 | 99 ab | 99 ab | 99 ab | 1.3 a | 0.0 a |
Glyphosate | 675 | 48 cd | 91 | 98 bc | 99 ab | 99 ab | 4.9 b | 0.3 a |
Glyphosate + AMS | 675 + 2.5 L∙ha−1 | 57 cd | 95 | 99 ab | 98 b | 99 ab | 2.8 ab | 0.2 a |
Glyphosate | 1181 | 64 bc | 98 | 99 ab | 100 a | 99 ab | 2.1 ab | 0.1 a |
Glyphosate | 900 | 52 cd | 97 | 99 ab | 99 ab | 100 a | 1.9 ab | 0.2 a |
Glyphosate + AMS | 900 + 2.5 L∙ha−1 | 57 cd | 98 | 99 ab | 99 ab | 99 ab | 1.9 ab | 0.0 a |
Glyphosate | 1406 | 82 ab | 100 | 100 a | 100 a | 99 ab | 1.2 a | 0.0 a |
aAbbreviations: AMS, ammonium sulfate; WAT, weeks after herbicide application. Means followed by the same letter within a column are not significantly different according to Fisher’s Protected LSD at P < 0.05.
Control | ||||||||
---|---|---|---|---|---|---|---|---|
Treatment | Rate | 1 WAT | 2 WAT | 3 WAT | 4 WAT | 8 WAT | Density | Dry weight |
g∙ae∙ha−1 | % | #/m2 | g/m2 | |||||
Weedy check | 0 | 0 | 0 | 0 | 0 | 11.1 c | 11.3 b | |
Weed-free check | 100 a | 100 a | 100 a | 100 a | 100 a | 0 | 0 | |
Glyphosate | 450 | 90 c | 98 c | 97 c | 97 c | 96 c | 3.5 b | 0.7 a |
Glyphosate + AMS | 450 + 2.5 L∙ha−1 | 94 bc | 99 b | 99 b | 99 b | 98 bc | 2.6 ab | 0.5 a |
Glyphosate | 956 | 95 b | 100 a | 99 b | 100 a | 98 bc | 2.3 ab | 0.4 a |
Glyphosate | 675 | 95 b | 100 a | 99 b | 99 b | 97 cd | 2.3 ab | 0.3 a |
Glyphosate + AMS | 675 + 2.5 L∙ha−1 | 97 b | 100 a | 99 b | 99 b | 99 b | 1.5 ab | 0.1 a |
Glyphosate | 1181 | 95 b | 100 a | 99 b | 99 b | 99 b | 1.0 ab | 0.0 a |
Glyphosate | 900 | 97 b | 100 a | 99 b | 100 a | 99 b | 0.8 a | 0.1 a |
Glyphosate + AMS | 900 + 2.5 L∙ha−1 | 96 b | 100 a | 99 b | 99 b | 99 b | 1.4 ab | 0.2 a |
Glyphosate | 1406 | 97 b | 100 a | 100 a | 99 b | 98 bc | 2.1 ab | 0.3 a |
aAbbreviations: AMS, ammonium sulfate; WAT, weeks after herbicide application. Means followed by the same letter within a column are not significantly different according to Fisher’s Protected LSD at P < 0.05.
Control | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|
Treatment | Rate | 1 WAT | 2 WAT | 3 WAT | 4 WAT | 8 WAT | Density | Dry weight | Yield | |
g∙ae∙ha−1 | % | #/m2 | g/m2 | T/ha | ||||||
Weedy check | 0 | 0 | 0 | 0 | 0 | 64.7 b | 24.5 b | 2.04 b | ||
Weed-free check | 100 a | 100 a | 100 | 100 a | 100 a | 0 | 0 | 3.40 a | ||
Glyphosate | 450 | 91 d | 99 b | 100 | 99 b | 98 b | 0.9 a | 0.2 a | 3.23 a | |
Glyphosate + AMS | 450 + 2.5 L∙ha−1 | 95 c | 100 a | 100 | 99 b | 99 b | 0.4 a | 0.1 a | 3.27 a | |
Glyphosate | 956 | 96 bc | 100 a | 100 | 99 b | 99 b | 0.3 a | 0.0 a | 3.34 a | |
Glyphosate | 675 | 96 bc | 100 a | 100 | 99 b | 98 b | 0.6 a | 0.1 a | 3.29 a | |
Glyphosate + AMS | 675 + 2.5 L∙ha−1 | 97 bc | 100 a | 100 | 99 b | 99 b | 0.5 a | 0.0 a | 3.41 a | |
Glyphosate | 1181 | 97 bc | 100 a | 100 | 99 b | 98 b | 0.6 a | 0.0 a | 3.42 a | |
Glyphosate | 900 | 97 bc | 100 a | 100 | 99 b | 99 b | 0.3 a | 0.0 a | 3.36 a | |
Glyphosate + AMS | 900 + 2.5 L∙ha−1 | 97 bc | 100 a | 100 | 99 b | 99 b | 0.5 a | 0.0 a | 3.44 a | |
Glyphosate | 1406 | 98 b | 100 a | 100 | 99 b | 98 b | 0.4 a | 0.0 a | 3.46 a | |
aAbbreviations: AMS, ammonium sulfate; WAT, weeks after herbicide application. Means followed by the same letter within a column are not significantly different according to Fisher’s Protected LSD at P < 0.05.
(SAS) [
Data were pooled and averaged over years and locations when there was no statistically significant interaction between year, location and treatments (Tables 1-9). Weeds were included when present in 3 or more trials.
There was no observable corn injury for any of the treatments tested (data not shown). For corn trials the predominant weed species included velvetleaf, common ragweed, common lambsquarters, Eastern black nightshade and barnyardgrass.
Glyphosate applied at 450, 675 and 900 g∙ae∙ha−1 controlled velvetleaf 90% - 98%, 96% - 99% and 98% - 100%, respectively (
Glyphosate applied at 450, 675 and 900 g∙ae∙ha−1 controlled common ragweed 80% - 97%, 85% - 99% and 86% - 99%, respectively (
Glyphosate applied at 450, 675 and 900 g∙ae∙ha−1 controlled common lambsquarters 91% - 99%, 93% - 100% and 94% - 100%, respectively (
Glyphosate applied at 450, 675 and 900 g∙ae∙ha−1 controlled Eastern black nightshade 82% - 100% (
Glyphosate applied at 450, 675, 900 g∙ae∙ha−1 controlled barnyardgrass 73% - 97%, 75% - 99% and 80% - 100%, respectively (
Reduced weed interference with glyphosate applied at 450, 675, 900 g∙ae∙ha−1 resulted in corn yields that were equivalent to the weed-free check (
Results are similar to other studies that have shown no improvement in control of velvetleaf, redroot pigweed, common lambsquarters and annual grasses when AMS was added to glyphosate [
There was no observable soybean injury for any of the treatments tested (data not shown). For soybean trials the predominant weed species included common ragweed, common lambsquarters, barnyardgrass and green foxtail.
Glyphosate applied at 450, 675 and 900 g∙ae∙ha−1 controlled common ragweed 37% - 89%, 58% - 93% and 65% - 97%, respectively (
Glyphosate applied at 450, 675 and 900 g∙ae∙ha−1 controlled common lambsquarters 39% - 98%, 48% - 99% and 52% - 100%, respectively (
Glyphosate applied at 450, 675 and 900 g∙ae∙ha−1 controlled barnyardgrass 90% - 98%, 95% - 100% and 97% - 100%, respectively (
Glyphosate applied at 450, 675 and 900 g∙ae∙ha−1 controlled green foxtail 91% - 100%, 96% - 100% and 97% - 100%, respectively (
Reduced weed interference with glyphosate applied at 450, 675 and 900 g∙ae∙ha−1 resulted in soybean yields that were equivalent to the weed-free check (
The addition of AMS or an equal dollar value of glyphosate to glyphosate applied at 450, 675 or 900 g∙ae∙ha−1 provided no consistent benefit for the control of velvetleaf, common ragweed, common lambsquarters, Eastern black nightshade and barnyard- grass in corn and common ragweed, common lambsquarters, barnyardgrass and green foxtail in soybean. There was no difference in corn or soybean yield among the herbicide treatments evaluated. The similar levels of weed control provided by the herbicide treatments evaluated provide a plausible reason for there being no effect of adding AMS or additional glyphosate to glyphosate on corn or soybean yield. Based on these results, the addition of AMS to glyphosate at the full label rate had little benefit on weed control efficacy and corn and soybean yield under Ontario environmental conditions.
The authors acknowledge Todd Cowan, Lynette Brown and Elaine Lepp for their expertise and technical assistance in these studies. This research was funded in part by the Grain Farmers of Ontario (GFO) and the GF2 program of the Agricultural Adaptation Council.
Soltani, N., Nurse, R.E., Shropshire, C. and Sikkema, P.H. (2016) Benefit of Adding Ammonium Sulfate or Ad- ditional Glyphosate to Glyphosate in Corn and Soybean. Agricultural Sciences, 7, 759- 770. http://dx.doi.org/10.4236/as.2016.710070