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Effects of Trinexapac-Ethyl on Perennial Ryegrass in Manitoba

2012 Research Report
Kevin Gulay B. Sc. (Agric)
MFSA Research Manager

Introduction
Manitoba producers have shown a lot of interest in the use of Trinexapac-Ethyl (TXP) in perennial ryegrass seed crops in Manitoba. TXP is widely accepted in the United States, and around the world, for use on perennial ryegrass, to reduce lodging. Once a crop is lodged there are increases in disease, and reduced pollination, which ultimately effect yield. A 2002 study in Oregon found a yield of 1490 lbs/A in perennial ryegrass treated with TXP, compared to a yield of 1080 lbs/A in the untreated check (Silberstein1 et al, 2002). TXP also significantly reduced the lodging of perennial ryegrass (Silberstein1 et al, 2002). Another study in Oregon, in 2002, found a yield of 1384 lbs/A in perennial ryegrass treated with TXP, compared to a yield of 1060 lbs/A in the untreated check (Silberstein2 et al, 2002). Yield increases with TXP were significantly higher when applied at onset, second node, and flag leaf, compared to a later application at early or full heading stages (Silberstein2 et al, 2002). The Manitoba Forage Seeds Association (MFSA) has also researched the use of growth regulators in the past. A report in 2006 shows annual rye grass to increase in yield from 1167 kg/H to 1487 kg/H with an application of TXP at the first node stage (Burak, 2006). Chlomequat is another plant growth regulator that has the potential to increase perennial ryegrass seed yield. Ryegrass growers in New Zealand reported 10-15% seed yield increases on their farms, however chlormequat did not control lodging (Rolston et al, 2004). The Manitoba Forage Seeds Association decided to conduct further research with TXP and chlormequat on perennial ryegrass in Manitoba conditions. Without registration of growth regulators in Canada, growers feel like they are at a disadvantage to their competition in the US. Hopefully this study emphasises how important it is for Manitoba producers to have access to this product.

Methods and Materials
Three sites were selected to test TXP in perennial ryegrass. The first site was located in Springstein on the NE 34-9-1W. Another site was located in Morris on river lot 407. The final site was located in Beausejour on the SE 13-13-7E. Products and rates tested can be seen below:
Table 1. Growth regulators and rates used in the study.
Individual plots were two meters by six meters in size, and all treatments were replicated four times, for a total of twenty plots per site. All plant growth regulator applications took place with a push type bicycle sprayer. Water volumes applied were fourteen US gal/A, and the boom height was approximately twenty inches above canopy. All applications took place May 30th under good environmental conditions. The Springstein and Morris sites were at a two node stage, and the Beausejour site was at a one node stage.
Lodging ratings were taken just before swathing. This timing was chosen so that growers can use this information to help decide how much of an effect each product will have on ease of swathing.
Springstein and Morris sites were hand cut for harvest on July 18th, 2012. The Beausejour cutting took place July 20th, 2012. One meter by three meter samples were taken from each plot. Samples were allowed to dry and then run through a Wintersteiger plot combine. The seed was then cleaned and weighed to obtain yield data.
Statistical interpretation was then done on the yield and lodging data.

Results
Significant differences were observed in the lodging of perennial ryegrass due to the application of plant growth regulators. Average results from all three sites are tabulated in table 2 below. A lodging rating of 5 means that none of the crop is lodged, while a lodging rating of 1 means that the entire crop is lodged. There was a statistical decrease in lodging with the chlormequat application. However, the decrease in lodging resulting from TXP was much more significant and very noticeable.
Table 2. Average lodging ratings from growth regulators.
Some yield differences were observed at the trials. Chlormequat actually lowered the yield compared to the untreated check. However, a noticeable yield increase was observed with the TXP. The TXP 2X was the highest yielding treatment.
Table 3. Average yield data across all sites.
Discussion
Swathing can be very challenging with perennial ryegrass crops in Manitoba. It appears that TXP will be a good tool to use to reduce the lodging of PRG. When fields were scouted two weeks after application, it was very noticeable which plots received the TXP. Those plots were shorter, and no lodging had occurred. At this point the plots treated with Chlormequat looked pretty much the same as the untreated check. As the growing season progressed, the TXP 1X began to elongate again. Eventually there was some lodging, but lodging took place much later than it did in the untreated check. This may have allowed for improved pollination in the TXP 1X perennial ryegrass, while the crop was still standing. Stem elongation in the TXP 2X perennial ryegrass, after the growth regulator application, was very limited. Plants remained short throughout the growing season, and the crop was very thin, to the point where it may have become difficult to make a swath row. As might be expected with lodging data, there was some variations amongst the sites. This resulted in some high coefficient of variations for the individual treatments. In this case, overall lodging pressure was greater in Springstein, than it was in Beausejour or Morris. For example, at the end of the season, the TXP 1X rate at Springstein lodged significantly more than it did at Morris or Beausejour.
This trial confirms that TXP can be used to increase the yield of perennial ryegrass. A 9% yield increase over the untreated check was found with TXP 1X, and a 15% yield increase with the TXP 2X. Previous studies, in other regions, have shown greater increases than this one. This may be attributed to the fact that while there were some good rains early in the season; the remainder of the season was hot and dry. This limited the yield potential of the perennial ryegrass, as well as the potential yield increase from the TXP.
There is more research that should be done to determine optimum TXP rates in Manitoba. There is a wide range of rates that may be applied, and a split application is even a possibility. Further, it may be beneficial to look at increasing nitrogen rates and the effect that that has when combined with TXP. If the perennial ryegrass won’t lodge with increasing nitrogen rates, than perhaps we can expect even greater yields.

Conclusion
Properly used, growth regulators can be used to reduce lodging, and increase the yield of perennial ryegrass seed crops in Manitoba. Lodging was reduced with the use of chlormequat and greatly reduced with the use of TXP. While a yield reduction was observed with the use of chlormeqaut, the use of TXP was found to increase the seed yield of perennial ryegrass crops. In the future, if Manitoba perennial ryegrass seed growers have the option of using TXP, they will be more competitive in the global market.
The MFSA would like to thank the PESAI for funding this project, as well as the growers who allowed the MFSA to use their land this project.
References
Burak, R. Plant Growth Regulators on Grass Seed Crops. 2006. Forage Seed News. Winter 2006: 43-44.
Rolston, M.P., B.L. McCloy, N.B. Pyke. 2004. Grass Seed Yields Increased With Plant Growth Regulators and Fungicides. Proceedings of the New Zealand Grasslands Association. 66: 127-132.
Silberstein1, T.B., W.C. Young, T.G. Chastai, C.J. Garbacik. 2002. Response of Perennial Ryegrass to Spring Nitrogen Fertility and Plant Growth Regulator Applications. Crop Science Society of America. 37(6): 1836-40. Seed Production Research at Oregon State University. 2002: 19-23.
Silberstein2, T.B., W.C. Young, T.G. Chastai, C.J. Garbacik. 2002. Response of Perennial Ryegrass to Timing of Plant Growth Regulator Applications. Seed Production Research at Oregon State University. 2002: 19-2

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