Roundup Ready Alfalfa Trials, Preliminary Results 2006-2007

Roundup Ready Alfalfa Trials
Preliminary Results 2006-2007

Four types of trials have been conducted with Roundup Ready alfalfa in recent years.

1. Seeding Rate Experiments to determine if it is realistic to reduce establish cost by reducing the seeding rate of RR alfalfa. This includes trials established Spring 2006 at Haskell and Bixby.

2. Roundup Ready vs Conventional alfalfa and herbicides trials compare the performance of a RR alfalfa variety and Roundup herbicide with a conventional variety and herbicides. This includes trials established at Perkins and Chickasha in fall 2005 and trials at Haskell and Bixby sown in spring 2006.

3. Alfalfa variety tests to compare variety yields, including private and public material. Five trials have included both RR and conventional varieties. Stillwater (3), Perkins (1), and Chickasha (1).

4. A pasture trial was initiated at Haskell to examine the possibilities of using Roundup Ready Alfagraze and Roundup Herbicide to establish alfalfa in bermudagrass and tall fescue pastures for grazing.

1. Seeding Rate Experiments - Part of a multi-state activity with Monsanto. Conditions and treatments include:

- Four seeding rates – 8, 12, 16, 20 lbs/acre;
- One variety – Roundup Ready – DK RR05
- Three herbicides - None, Beyond, Roundup
- Two locations - Haskell, which was rainfed and had few weeds; and Bixby – which was irrigated and had many vigorous weeds.
- Date Sown - April 6, 2006

Data collected included:
- Stand density – alfalfa and weeds (5 observations)
- Ground coverage by alfalfa - percent at the end of the growing season.
- Yield – alfalfa and weeds at each of 3 harvests at Bixby and 2 harvests at Haskell
- Forage Composition – proportion of alfalfa, broadleaf weeds, grass weeds at each harvest.
- Forage quality - CP, RFV, RFQ, ADF, NDF, ADL, IVTD, TDN, ASH, Milk/ton for each harvest.

Stand Density Results: Tables 1-4 include stand data from Bixby and tables 5-8 include stand data from Haskell. The early stand counts were uniform, and the seeding rates resulted in a good gradation of stand densities. Stands decreased at both locations from June to October but no herbicide effect or interaction was significant. Density differences among seeding rates became smaller but remained significant. Percent ground cover by alfalfa data in Tables 9 and Table 10 indicated the Roundup-treated plots had higher percent coverage by alfalfa, followed by Beyond and then by no herbicide at Bixby. The same trend was observed at Haskell but the means were much closer. Seeding rates affected the ground coverage more at Bixby than at Haskell.

Yield Results: At Bixby (Table 11 and 12) higher seeding rates yielded more alfalfa than low rates, and Roundup controlled weeds completely. When the yield of weeds and alfalfa were included together, yield was not significant among seeding rates and “no herbicide” had the highest yield. At Haskell (Table 13 and 14) both Roundup and Beyond completely eliminated the weeds, but seeding rates did not significantly affect the pure alfalfa yield or alfalfa plus weeds yield. The weed component at Haskell was much less than at Bixby and alfalfa yields were lower as well.

Forage Composition Results (Figure 1): At Bixby the proportion of the forage made up of weeds increased through the season but was not strongly affected by seeding rate except at second harvest where the broadleaf weeds represented more than 30 % of the forage averaged across the herbicides. This contrasts to the herbicide effect where alfalfa represented only 15 to 30% of the forage when no herbicide was applied at Bixby. Roundup-treated plots consistently resulted in 100 % alfalfa. At Haskell weed infestation was so small that neither herbicide nor seeding rate affected percent composition.

Forage Quality Results: Seeding rate had almost no affect on any of the forage quality measurements at both locations (Tables 15-23 Bixby and Haskell). The plots treated with herbicides tended to produce higher quality forage (weeds included) than without herbicide at both locations, but there was little difference between the herbicides. Surprisingly, there were no significant interactions between herbicide treatments and seeding rates.

2. Roundup Ready vs Conventional Alfalfa: At Bixby where weeds were prolific and competitive, the combination of the RR alfalfa variety and Roundup herbicide produced yields much higher than the conventional or no herbicide (with either variety) (Table 24). Results from the other three trials were different. There were few weeds and the weeds did not compete with alfalfa enough to decrease yield. Consequently controlling the weeds did not increase forage yield. With a few exceptions the conventional alfalfa varieties (OK 49 or HybriForce 600) tended to have somewhat higher yields than the RR varieties (DKA41-18RR and FD4RRA)(Table 25-27 Haskell, Perkins, Chickasha).

3. Alfalfa Variety Tests: Only one of the five variety tests containing conventional and RR varieties has more than one year’s data, and two of those sown in 2005 produced low yields because of droughty conditions in 2006. Nevertheless, there is a tendency for the RR varieties to produce poorly compared to the conventional varieties. It is unlikely that this trend is because of the RR gene. It is more likely due to the background of the varieties and that they were not selected for production in the southern Great Plains. Stillwater 2-yr, Stillwater 1-yr, Stillwater 1-yr, Perkins, Chickasha

4. Pasture Trial with Alfagraze 300RR: Grazing pure alfalfa stands through the growing season has not had much appeal for many in Oklahoma. Establishing and maintaining alfalfa in pastures along with grasses has long been desired. As the price of nitrogen fertilizer remains high and many producers are looking for ways to grow their own nitrogen, we are looking at grazing alfalfa again.

Many attempts to establish alfalfa into tall fescue have been partially successful but maintaining the legume has been difficult at best. Establishing alfalfa into bermudagrass has been extremely difficult and usually futile.

Two things have happened recently to make us look at grazing alfalfa again. ‘AlfaGraze’, released in 1991, was the first dual purpose alfalfa cultivar with high yield that persists under intensive grazing and led the way for future grazing tolerant cultivars. The transgene, Roundup Ready®, the initial biotech trait in alfalfa, provides tolerance to the herbicide Roundup® (glyphosate). ‘AlfaGraze 300 RR’ and ‘AlfaGraze 600RR’ are Roundup Ready® varieties with tolerance to grazing and improved pest resistance.

The following is a preliminary report of an activity at the Eastern Research Station near Haskell, OK. The purpose of this research/demonstration is to investigate ways to utilize grazing tolerance and Roundup Ready® traits to improve the success of establishing alfalfa into grass stands in pastures. Once alfalfa is established and growing with grass, the next step is to identify ways to maintain the alfalfa for several years while grazing.

This is a qualitative interim report on the results of several different components of the methodology. Because no quantitative data was recorded and a picture is sometimes worth a thousand words, images on the web serve as the results of this activity. Links for are given below to particular sets of images for several different dates or subjects. These images may also be viewed by going to http://alfalfa.okstate.edu then “Images” à “Special Image Collection” à “Roundup Ready Alfalfa Spring & Summer 2006”. From there one can navigate to various dates and back.

Alfagraze 300 RR was planted into existing stands of bermudagrass and tall fescue on 4 April 2006 at the Eastern Research Station near Haskell, OK. The pasture was a combination of droughty tall fescue and dormant bermudagrass along with cool-season annual grasses. The soil was just dry enough after the first rain of any significance since the previous fall (about 5 months). Seed went into moist soil and germinated quickly. Following planting was several weeks of no rain and many hot (90F+) days with wind through the end of April. In mid May alfalfa plant counts in quadrats showed an average of a little more than 1 alfalfa plant per square foot, but highly variable (typical of pasture observations).

On 17 May 2006 when the grasses were again dormant due to dry soil conditions Roundup was applied in strips, 1’, 3’, or 5’ wide and 100+’ long at the rate of 22 oz/acre and 44 oz/acre in the strips to kill or suppress competing vegetation. The strips of Roundup were made perpendicular to the drill rows of alfalfa. No difference in bermudagrass death (or suppression) between the 22 and 44 oz/acre could be observed as both were effective in spite of the dry weather and generally poor growing conditions.

Soil fertility and depth in these pastures are highly variable but adequate for reasonably good forage production. Soil pH was approximately 6.0 and soil test P and K were approximately 85% sufficient.

Images showing the appearance of the pastures on 31 May 2006 are available at http://alfalfa.okstate.edu/images/RRAlfalfa/AlfagrazeRR5-31-06/RRAlfalfaHaskellPastures.htm If the Roundup had not been applied, essentially no alfalfa would have been present. Alfalfa was small but growing well where Roundup was applied.

Bermudagrass and tall fescue were again dormant due to dry weather at the end of June. Alfalfa plants without competition were growing well. Alfalfa plants in bermudagrass that was not sprayed were much shorter and fewer plants survived.

Images illustrating the conditions and progress as of 29 June 2006 are available at http://alfalfa.okstate.edu/images/RRAlfalfa/AlfagrazeRR6-29-06/rralf-pasture6-29-06.htm

Our next visit and photo session was 3 August 2006. It was dry, but rows of alfalfa could be seed where bermudagrass was sprayed with Roundup. Little or no alfalfa existed where bermudagrass was not sprayed with Roundup. Alfalfa plants that were still alive looked good after grazing for about 30 days and mowing to even out the vegetation in the area. Images illustrating the appearance of the pastures with alfalfa on 3 August 2006 are available at http://alfalfa.okstate.edu/images/RRAlfalfa/AlfagrazeRR8-3-06/alf-grzRR.htm

This was one of the hottest summers on record and rainfall was limited to about 60% of average.
Temperature (F)
April - 5 days above 90
May - 8 days above 90
June - 17 days above 90
July - 29 days above 90 (10 days above 100)

Rainfall (inches)
Jan 1.20
Feb 0.52
March 2.38
April 4.40
May 4.19
June 1.27
July 2.67
TOTAL = 16.63

By 31 August 2006 bermudagrass had begun to grow back into the sprayed strips. Alfalfa plants and crowns were small but adequate for a spring-sown stand that had been grazed for two months. Alfalfa plants that became established in the non-sprayed bermudagrass are excessively small or dead. Alfalfa in the roundup-sprayed strips was clearly in drill rows. The stand was less than would probably be found in a clean-tilled field, but more than adequate for pastures. Views of the area on 31 August 2006 are available at http://alfalfa.okstate.edu/images/RRAlfalfa/AlfagrazeRR8-31-06/alf-grzRR.htm

By the end of September, with cooler temperatures and a few rains, the pastures were productive with alternating strips of bermudagrass and alfalfa. Some tall fescue was observed. Images of the spring-sown alfalfa in pastures on 29 September 2006 are available at http://alfalfa.okstate.edu/images/RRAlfalfa/AlfagrazeRR9-29-06/AlfaGraze2006.htm

By early November bermudagrass had stopped growing due to cold weather and was stockpiled for grazing later. Alfalfa was clearly productive and providing abundant forage in areas planted in the spring. Images of 1 November 2006 are available at http://alfalfa.okstate.edu/images/RRAlfalfa/AlfagrazeRR11-1-06/RRAHaskellAprilSown.htm

Where grasses were suppressed with Roundup, September-sown alfalfa was small but growing well in early November. Images of 1 November 2006 are at http://alfalfa.okstate.edu/images/RRAlfalfa/AlfagrazeRR11-1-06/RRAHaskelSeptSown.htm

Freezing temperatures stopped bermudagrass growth, but alfalfa continued to grow into the fall. stockpiled bermudagrass along with alfalfa for both spring- and fall-sown stands were grazed in December for 3 to 5 days with about 56 cow-calf pairs so that little alfalfa was left about a few inches high. As bermudagrass regrows during next spring it will encroach into the alfalfa but can be suppressed again with Roundup as needed to maintain a mixture of grass and legume.

Cool-season grasses along with dormant bermudagrass and alfalfa were grazed in early January 2007. January 2007 images spring-sown stands may be seen at http://alfalfa.okstate.edu/images/RRAlfalfa/alfagrazeRR1-10-07/alfagraze-haskell1-07.htm
and fall-sown stands can be seen at http://alfalfa.okstate.edu/images/RRAlfalfa/alfagrazeRR1-10-07/alfagraze-haskell1-10-07.htm. Abundant precipitation during November through January and short bermudagrass and tall fescue stubble height encourages both legumes and cool-season annual grasses to become established.