Preharvest Applications Of Glyphosate Research Articles

Kochia (Bassia scoparia) harvest date impacts nutrient composition, in vitro degradability, and feed value more than pre-harvest herbicide treatment or herbicide resistance traits

Kochia is a summer-annual tumbleweed that is drought, saline, and heat tolerant, and often resistant to several herbicides. Glyphosate-resistant kochia exhibits indeterminate growth and remains green during senescence, making it difficult to harvest crops that are contaminated with this weed. Removing dense patches of kochia from contaminated crops can aid in downstream harvest operations while also generating a potential source of livestock feed. This study evaluated the effects of two kochia populations [glyphosate-resistant (GR) and glyphosate-susceptible (GS) kochia] with or without pre-harvest treatment using glyphosate + saflufenacil [untreated (UN) vs treated 10 d pre-harvest (PRE)] on nutrient composition and in vitro degradability when it was harvested at advancing maturities. Kochia (GR-UN, GR-PRE, GS-UN, and GS-PRE) was harvested on 6 dates (HD) corresponding to pre-bloom (HD 1), mid-bloom (HD 2), full-bloom with 50% open flowers (HD 3), developing seeds (HD 4), mid-mature seeds (HD 5) and fully mature seeds (HD 6). In most cases, harvest date affected the chemical composition and in vitro degradability to a greater extent than the kochia population or herbicide treatment. The dry matter (DM) yield increased (P < 0.001) from HD 1–5 and decreased thereafter. The crude protein (CP) content decreased (P < 0.001) while the acid (ADF) and neutral detergent fiber (NDF) content increased (P < 0.001) with advancing HD. Overall, the CP content was higher (P = 0.014), and ADF content lower (P < 0.001) for GS than GR. Total in vitro gas (mL) (P < 0.001) and methane (CH4) production (mL L−1 of gas production) (P < 0.001) after 6 h incubation was greater for GR-UN than GR-PRE across HD. A decrease in acetate (P < 0.001) and an increase (P < 0.001) in propionate concentration with advancing HD led to reduced (P < 0.001) CH4 production after 48 h of in vitro incubation. Dry matter degradability (DMD; %) of GR-UN was greater (P = 0.003) than GR-PRE, while DMD and NDF degradability decreased (P < 0.001) with advancing HD. Pre-harvest application of glyphosate tended to increase the cell wall and decrease non-fibrous carbohydrate fractions, resulting in a slight decline in degradability and an increase (P < 0.05) in in vitro CH4 production. Further in vivo digestibility and growth performance studies using kochia harvested at the optimal maturity are required to define the value of this weed as forage in ruminant production systems.

Impact of glyphosate applied preharvest on oat kernel quality

AbstractBackground and objectivesPreharvest glyphosate is applied to oats for weed control and as a desiccant. The effect of glyphosate applied at various stages of oat physiological maturity on oat end product quality has not been reported previously. In this study, the effects of glyphosate application at two separate stages of physiological maturity on oat groat quality and rolled oats quality were determined.FindingsOat was grown at two locations. Glyphosate was applied at the soft dough, physiological maturity stages, or not applied. Effect of preharvest glyphosate application at the oat soft dough stage on groat hardness, groat percentage (0.7%–3.7% decrease by cultivar), and percent plump groats (0.3%–6.1% decrease by cultivar), when compared to untreated oats, was noticeable. However, glyphosate applied at physiological maturity (manufacturer's recommendation) did not detrimentally affect groat starch (average 60.3%) or end product quality.ConclusionsTherefore, from an end‐user perspective, applying glyphosate preharvest at oat physiological maturity does not impact oat quality.Significance and noveltyGlyphosate when applied preharvest to oats can control weed and facilitate harvest, a boon to farmers. Final oat quality, a decisive factor for commercial processor use, was not detrimentally affected when glyphosate was applied at oat physiological maturity.

Pre-harvest glyphosate application effects on properties of β-glucan from oat groats

Pre-harvest glyphosate is applied to cereal grains to control weed growth. However, it has been claimed that oat (Avena sativa L.) composition is affected by pre-harvest glyphosate application. The research was conducted to evaluate differences in properties of β-glucan in grains of pre-harvest glyphosate treated versus untreated oat plants. Two oat cultivars (Rockford and Souris) were grown at Minot and Prosper, ND, in 2015, and glyphosate was sprayed during the soft dough stage, hard dough stage, or not applied. β-glucan viscosity was not significantly (p > 0.05) affected by treatment at soft dough (1082 cP) or mature (1166 cP) stages compared with untreated (1150 cP) controls. Applying glyphosate at the soft dough stage significantly (p < 0.05) reduced the content and solubility of the β-glucan versus untreated samples. β-glucan content and solubility in oat treated at soft dough were 4.35% and 52.1%, respectively, while in untreated samples were 4.65% and 60.6%, respectively. Treatment at soft dough and hard dough stages significantly (p < 0.05) increased weight average molecular weight (Mw) of the high molecular weight fraction of soluble β-glucan (4.4 × 106 and 3.8 × 106, respectively), compared with untreated controls (3.5 × 106). The Mw of the low molecular weight fraction of soluble β-glucan fraction significantly (p < 0.05) increased at soft and hard dough treatments (5.5 × 105 and 3.3 × 105, respectively), versus untreated samples (3.0 × 105). Therefore, glyphosate can be applied when the grain has reached physiological maturity or thereafter.

Cover Image, Volume 44, Issue 8

The cover image is based on the Full Article Pre-harvest glyphosate application and effects on wheat starch chemistry: Analysis from application to harvest by Senay Simsek et al., https://doi.org/10.1111/jfbc.13330.

Effects of pre-harvest glyphosate use on protein composition and shikimic acid accumulation in spring wheat.

During wheat cultivation, glyphosate-based herbicides are recommended to be applied a week prior to harvest during the ripe stage of physiological maturity. However, some grains may not be at this physiological stage due to non-uniform maturation within the field. The goal of this study was to determine the effect of glyphosate-based herbicide timing on the chemistry of wheat gluten proteins and shikimic acid accumulation. The results of the study indicate that pre-harvest glyphosate application does not impact the amino acid composition, protein secondary structure or gluten protein composition. However, pre-harvest glyphosate application decreased the molecular weight of SDS extractable and unextractable proteins, and significantly increased the amount of shikimic acid accumulation, especially when applied early. Thus, this study indicates that pre-harvest use of glyphosate-based herbicides can cause significant differences in wheat protein chemistry and shikimic acid levels, especially when applied earlier than recommended, emphasizing the importance of timely application.

Pre-harvest glyphosate application and effects on wheat starch chemistry: Analysis from application to harvest.

The objective of this study was to determine if the pre-harvest glyphosate application time affects the chemistry of wheat starch. Glyphosate was sprayed at the ripe stage (recommended) and the soft dough stage (early application) of hard red spring wheat. Wheat kernel samples were collected before application and every 3days until harvest, after which different starch characteristics were analyzed. The results indicate that glyphosate timing does not impact the spatial distribution or morphology of starch granules, as well as the percentage or molecular weight of amylose and amylopectin. However, thermal characteristics of wheat starch, especially when glyphosate was applied at the soft dough stage, showed significant differences. A decrease in the average amylopectin chain length and differences in the proportion of short-, medium-, and long-chain amylopectin was also observed. Overall, this study shows that the pre-harvest application of glyphosate can affect wheat starch chemistry, especially if applied earlier than recommended. PRACTICAL APPLICATIONS: Glyphosate is the most commonly used herbicide in the world, and it is sometimes used pre-harvest during wheat cultivation. The recommended time of application is 7days prior to harvest when the crops are in the ripe stage of physiological maturity. However, some crops may not be at this stage during application due to non-uniform maturation in the field. The goal of this work was to determine the effect of glyphosate application time (recommended/ripe stage vs. early/soft dough stage) on wheat starch chemistry. The results show that the starch chain length characteristics and thermal behavior are impacted, especially if applied early. Thus, this study shows the importance of timely application to avoid effects on starch chemical properties, which in return could impact starch functionality in food systems. This information is critical in the field of agriculture and to our knowledge this study is one of the first in this area.

Effects of Pre-Harvest Glyphosate Application on Spring Wheat Quality Characteristics

This study was conducted to determine the effect of pre-harvest glyphosate application on spring wheat quality characteristics, ranging from kernel quality to baking quality. Two wheat cultivars were grown in three locations, and glyphosate was applied at the recommended rate at the soft dough stage (early application) and the ripe stage (recommended application time). When glyphosate was applied at the soft dough stage, kernel weight, wheat protein and wet gluten decreased significantly (p ≤ 0.05), however, gluten index significantly increased (p ≤ 0.05). Dough quality, farinograph stability, and quality number were significantly (p ≤ 0.05) higher when glyphosate was applied at the soft dough stage, and absorption and the mixing tolerance index were lower. As for baking quality, loaf volume and mix time were significantly (p ≤ 0.05) higher in the treated samples in comparison to the untreated control, and other baking quality characteristics did not show any significant difference. Overall, the results indicate that spring wheat quality characteristics are impacted to the greatest degree when glyphosate is applied earlier than recommended at the soft dough stage, as opposed to the recommended application at the ripe stage of physiological development.

Preharvest Glyphosate Application during Wheat Cultivation: Effects on Wheat Starch Physicochemical Properties.

Due to nonuniform maturation, some plants may not be at the recommended stage of maturity when preharvest glyphosate is applied. The objective of this study was to determine how preharvest glyphosate timing affects wheat starch physicochemical properties. Two wheat cultivars were grown in three locations, and glyphosate was applied at the soft dough stage (early application) and the ripe stage (commercial standard). Upon harvest, starch chemical characteristics were studied. The proportion of B-type starch granules was lower in treated samples, although the starch molecular weight was not affected. Rapidly digestible starch content was highest when glyphosate was applied at the ripe stage, and lowest in the control, and vice versa for slowly digestible starch. Additionally, flour pasting viscosity was significantly higher in samples treated at the soft dough stage. Overall, the effects on wheat starch physicochemical characteristics were more pronounced when glyphosate was applied at the soft dough stage of maturity.

The Effects of Preharvest Glyphosate With Ammonium Adjuvants on Grain Protein Content of Hard Red Spring Wheat

Laboratory and field experiments were conducted to investigate if glyphosate applied with ammonium fertilizers as adjuvant at or after physiological maturity (PM) would lead to an overestimation of grain protein content in hard red spring wheat (HRSW). In the laboratory experiment, grain was mixed with liquid and dry ammonium sulfate (AMS) or a urea ammonium nitrate (UAN) solution. A 15 lb N/acre and 148 lb N/acre equivalent of UAN led to an 11 and 42% overestimation of the grain protein content, confirming that adulteration of grain with ammonium fertilizers is possible. In the field experiment, treatments included an untreated control, water alone, a glyphosate solution, an AMS solution, a glyphosate solution with AMS, an UAN solution, and a glyphosate solution with UAN. The rates for glyphosate, liquid AMS, and liquid UAN were 0.77 lb acid equivalent/acre, 5.0 lb AMS/acre or 5% v/v, 5.3 lb UAN/acre or 5% v/v, respectively. The treatments were applied at PM, 5 days after PM, and 10 days after PM. Grains were harvested at 12 days after PM and grain protein content was determined immediately and 7 days after harvest. None of the glyphosate, AMS, and UAN combinations applied at the labeled rates at or post PM caused an overestimation of grain protein content. This means that it is highly unlikely that grain protein content in HRSW can be adulterated with an preharvest glyphosate application.

Preharvest Applications of Glyphosate Affect Emergence and Seedling Growth of Field Pea (Pisum sativum)1

Field experiments were conducted in 1994 and 1995 at Vegreville, Legal, and Lacombe, AB, to determine the effects of a preharvest application of glyphosate on seedling emergence and growth of field pea. Glyphosate was applied at 0.9 kg ai/ha at each of the three crop development stages, as determined by seed moisture content (SMC), to determinate (‘Ascona’ and ‘Radley’) and indeterminate (‘Miko’ and ‘Trapper’) cultivars. Applying glyphosate when the SMC was less than 30% had little to no effect on seedling emergence but reduced seedling shoot fresh weight in two of six experiments. Applying glyphosate at SMC above 40% reduced seedling emergence and shoot fresh weight in two and three of the six experiments, respectively. Reductions in seedling emergence and shoot fresh weight were greater from seeds collected from the top than from seeds collected from the bottom one-third of sprayed plants. Differences in response between determinate and indeterminate cultivars occurred, but there was no consistent trend. Given the variable maturity in most fields and on individual pea plants, applications of preharvest glyphosate to peas destined for seed production may decrease seed germination and biomass accumulation.Nomenclature: Glyphosate; field pea, Pisum sativum L. ‘Ascona’, ‘Miko’, ‘Radley’, ‘Trapper’.Additional index words: Crop desiccation, determinate and indeterminate pea cultivars, harvest aid.Abbreviations: SMC, seed moisture content.

Preharvest glyphosate in alfalfa for seed production: Effect on alfalfa seed yield and quality

Preharvest applications of glyphosate have been shown to be effective in controlling Canada thistle in annual crops, but may reduce alfalfa seed yield depending on time and rate of application. The objective of this study was to determine the effect of preharvest applications of glyphosate on subsequent alfalfa seed yield and quality. The effects of timing, 1, 26, 51 and 76% alfalfa seed pod maturity, and rate, 0, 440, 880, 1320, and 1760 g a.i. ha-1, of a preharvest application of glyphosate on alfalfa seed yield and quality in the year of application, and regrowth and seed yield in the following year were determined. The rate of glyphosate applied did not affect seed yield in the application year; however, in the following year, growth and seed yield were reduced as rates increased. Delaying the application of glyphosate increased seed yields in the application year, but decreased alfalfa regrowth and flowering the following year. Germination and seedling emergence were not affected by the rate or timing of the glyphosate. A preharvest application of glyphosate at 1760 g a.i. ha-1 at 76% pod maturity is a viable option in the last year of seed production. Key words: Alfalfa (Medicago sativa L.), glyphosate, abnormal seeds, seed quality, and seedling vigour

Residues of glyphosate and its metabolite AMPA in field pea, barley and flax seed following preharvest applications

Maximum residue levels have been established by Health Canada for seed of several crops treated with preharvest applications of glyphosate, a common practice on the Canadian prairies. Residues of glyphosate and its major metabolite aminomethylphosphonic acid (AMPA) were determined at crop maturity in flax seed at one site in western Canada and in the seed and straw of field pea and barley at another site following preharvest applications of the herbicide. Glyphosate was applied at rates of 0.45, 0.9 and 1.7 kg ha-1 to each crop in early August to mid-September at four stages of crop development. In all crops, mean residues of glyphosate and AMPA increased with increasing application rate of glyphosate and decreased when the herbicide was applied at later stages of crop development. Key words: Glyphosate residues, AMPA residues, barley, field pea, flax, preharvest treatment

Effect of preharvest applications of glyphosate on the drying, yield and quality of canola

Potential use of preharvest applications of glyphosate in canola (Brassica rapa L.) in western Canada both as a harvest aid and to control weeds prompted this study. Experiments were conducted from 1988 to 1990 at four locations in the region to document the effectiveness of preharvest applications of glyphosate to enhance canola seed and foliage drydown and to measure the effect of such applications on seed yield and quality. Glyphosate was applied in early August to early September at rates of 0.45, 0.90 and 1.70 kg acid equivalent ha−1 to canola with seed moisture contents ranging from 79 to 12%. Seed and foliage moisture drydown were not enhanced by glyphosate treatment. Glyphosate treatments generally had little or no effect on canola seed yields, seed weight, seed germination, green seed content or oil content except when applied when the pods were green and when seed moisture contents were high. Seed/pod moisture was not a reliable indicator of stage of canola development and thus, should not be used alone as an indicator of when preharvest applications of glyphosate can be applied to canola without decreasing seed yield and quality. Key words: Glyphosate, canola, Brassica rapa L., preharvest application, desiccation, seed quality

Residues of glyphosate and its metabolite AMPA in canola seed following preharvest applications

Residue data for glyphosate and its major metabolite aminomethylphosphonic acid (AMPA) in canola seed following preharvest application of glyphosate were lacking when this 2-yr study was initiated. Residues of glyphosate and AMPA were measured in the seed of canola (Brassica rapa L.) at maturity following preharvest application at rates of 0.45, 0.9 or 1.7 kg acid equivalent ha−1 at four sites in western Canada. Herbicide treatments were applied in early August to mid-September at four stages of crop development, which encompassed seed/pod moisture contents ranging from 74 to 12%. Rate of glyphosate application and the physiological maturity of the crop at application played important roles in determining the magnitude of glyphosate and AMPA residues in the seed of preharvest-treated canola. In general, for a given site, mean residues of glyphosate and AMPA in the seed increased with increasing application rate, and decreased with application at later stages of crop development. In 1989, mean residues of glyphosate in the seed for all application rates at the latest stage of development at each site were &lt;1 mg kg−1. In 1988, when seed/pod moisture content generally declined very slowly from stage 1 to stage 3 and then decreased rapidly, corresponding mean residues were higher and varied from &lt;1 to 19.7 mg kg−1. Seed/pod moisture was not a reliable indicator of stage of canola development and, consequently, the magnitude of glyphosate and AMPA residues in the seed. Key words: Glyphosate residues, AMPA residues, canola, preharvest treatment

Effect of Preharvest Glyphosate Application on Seed and Seedling Quality of Spring Wheat (Triticum aestivum)1

Studies were conducted to determine effects of preharvest applications of glyphosate on the seed and seedling quality of ‘Alpowa’ and ‘Penawawa’ soft white spring wheat (Triticum aestivum) varieties. Glyphosate was applied at 0.62 or 0.84 kg ae/ha at the milk (Zadoks' scale 70 to 79), soft dough (Zadoks' scale 85), or hard dough stage (Zadoks' scale 87) of wheat development; 7 d following the hard dough treatment; and 1 d prior to wheat harvest. In harvest aid applications, wheat yields were reduced only with glyphosate applied at the milk stage of development. Yield reduction ranged from 20 to 77% depending on the year, variety, and glyphosate rate. Likewise, kernel weight and germination were affected only by glyphosate applications at the milk stage with reductions from 19 to 73% and from 2 to 46% for kernal weight and percent germination, respectively, compared to untreated wheat. Using wheat from harvest-aided glyphosate treatments at the milk stage as seeds the following year resulted in reductions ranging from 28 to 99%, 19 to 39%, and 12 to 97% for seedling density, plant height, and seed yield, respectively, compared to seeds from untreated wheat. In this study, wheat seed and seedling quality following preharvest glyphosate applications were most greatly influenced by crop maturity stage at time of application than by herbicide rate or variety.Nomenclature: Glyphosate, N-(phosphonomethyl)glycine; spring wheat, Triticum aestivum L. ‘Alpowa,’ ‘Penewawa.’Additional index words: Desiccation, germination, harvest aid, herbicide.

Glyphosate or sethoxydim for quackgrass (Elytrigia repens) control in two tillage regimes

Field experiments were conducted at Lacombe and Ellerslie, Alberta, Canada, to study the interaction of tillage with glyphosate and sethoxydim on quackgrass shoot and rhizome biomass, rhizome bud viability, and crop yield. Glyphosate was most effective in the conventional tillage regime, whereas sethoxydim was effective only in conventional tillage. Tillage reduced viable rhizome buds more than shoot or rhizome biomass. The large tillage effect on quackgrass control with either herbicide would likely be diminished in zero tillage systems that employ preseeding burn-off or preharvest application of glyphosate. Under zero and conventional tillage, glyphosate at 220 g ha−1often was as effective as glyphosate at 880 g ha−1.A split application of glyphosate at 220 g ha−1in the fall and spring was as effective as a single 880 g ha−1treatment in conventional tillage, and sometimes more effective than 880 g ha−1in zero tillage. Glyphosate followed by sethoxydim was usually no better than glyphosate alone. Short-term split applications of sethoxydim offered no consistent advantage over single applications.

Effect of preharvest applications of glyphosate on the drying, yield and quality of wheat

In experiments conducted from 1988 to 1990 at four locations in the Parkland zone of western Canada, the drydown of seed and foliage, seed yield, seed quality and baking quality of wheat (Triticum aestivum L.) following preharvest applications of glyphosate were compared with those following windrowing prior to harvest or direct cutting of the standing crop. Glyphosate was applied in late July to early September at rates of 0.45, 0.9 and 1.7 kg acid equivalent ha−1 to wheat with seed moisture contents ranging from 80 to 11%. When compared with a standing crop, all glyphosate treatments applied at seed moisture contents above 25% slightly enhanced the drydown of wheat seed and foliage. Treatments applied at seed moisture contents below 25% had no effect on either seed or foliage drydown. Seed yields were generally greater from plots to which glyphosate was applied than from windrowed control plots, although in one of five experiments the reverse trend occurred. Increasing the rate from 0.45 to 1.7 kg ha−1 had no effect on yield. Windrowing or applying glyphosate to wheat with a seed moisture content of 61% or more reduced yields more than windrowing or applying glyphosate at seed moisture contents below this level. In experiments where the wheat in both control and sprayed plots was direct cut at maturity, average yields decreased as the rate of glyphosate increased from 0 to 1.7 kg ha−1. However, applications at seed moisture of 40% or less, caused little or no yield loss. There was little or no difference in 1000-seed weight, sample density, seed germination and protein content from plots sprayed with glyphosate at seed moisture contents below 40% than from control plots windrowed at the same moisture content or direct cut at maturity. Baking quality was not affected by any of the glyphosate treatments in experiments where the wheat was harvested by direct cutting. Key words: Glyphosate, wheat, desiccation, wheat quality, Triticum aestivum