THE FLORIDA CATTLEMAN AND LIVESTOCK JOURNAL
Methods of Establishing Annual Ryegrass into Bahiagrass Sod Affects Forage Botanical Composition, Production, and Nutritive Value
Bahiagrass is the predominant warm-season grass used for cow-calf production in Florida. Bahiagrass is productive during the warm-season; however, the herbage accumulation is limited during the winter due to decreased temperatures and daylength.
Mild winters in Florida offer producers the opportunity to cultivate cool-season annual forages during the period when productivity of bahiagrass is limited. Advantages of using cool-season annual grasses as winter pastures include extending the grazing period, high nutritive value, compatibility and relatively easy of establishment in warm-season perennial grass pastures, and tolerance to different defoliation regimes and stocking rates. Annual ryegrass is the most planted cool-season forage in South Florida.
In South Florida, warm autumns and late first frost favor bahiagrass during establishment of annual ryegrass. In order to decrease this competition, it is recommended to seed annual ryegrass in late autumn or early winter. This management practice may favor the establishment of the annual ryegrass; however, it decreases the cool-season grazing period. Establishment cost and length of the grazing season are the two most influential factors in the economic feasibility of planting annual ryegrass in South Florida. Considering the late planting and the intrinsic subtropical climate of South Florida, it is necessary to identify methods of establishment which can increase annual ryegrass forage production while minimizing the impacts on the subsequent bahiagrass production and persistence.
Therefore, a research project was conducted at the UF/IFAS Range Cattle Research and Education Center with the objective to evaluate annual ryegrass production and nutritive value, and bahiagrass persistence, production, and nutritive value using different methods of annual ryegrass establishment.
The study was conducted on an established bahiagrass pasture at the University of Florida Range Cattle Research and Education Center at Ona, FL from November 2006 to November 2008. The treatments were: 1) annual ryegrass broadcast-seeded on the bahiagrass undisturbed sod, 2) annual ryegrass broadcast-seeded on light-disked bahiagrass sod, 3) annual ryegrass broadcast-seeded on glyphosate-treated bahiagrass sod, 4) annual ryegrass broadcast-seeded on paraquat-treated bahiagrass sod, and 5) annual ryegrass broadcast-seeded on a prepared seedbed. The Control was bahiagrass sod not overseeded.
The plots were 50 x 20 ft and were clipped to a 2.8-inch stubble height with a flail-harvester immediately before applying the treatments. The disking on the light-disked bahiagrass sod treatment was done using a dual tandem disk-harrow at a shallow setting (3 inches) to cut the sod and loosen the soil. The chemical treatments were sprayed with either glyphosate (1.2 lb a.i./acre) or paraquat (0.08 lb a.i/acre) 3 weeks before seeding the annual ryegrass using a backpack sprayer calibrated to deliver 30 GPA. The prepared seedbed treatment consisted of disking the sod with a dual tandem disk-harrow several times until there was no remaining vegetation on the soil surface. ‘Jumbo’ annual ryegrass was broadcast-seeded at the seeding rate of 22 lb/acre and the experimental units were rolled to ensure adequate contact between seed and soil.
The annual ryegrass was seeded on 10 November 2006 and 19 November 2007. The plots were fertilized with 50 lb N/acre, 22 lb P/acre, and 42 lb K/acre approximately 2 weeks after seeding. An additional 60 lb N/acre was applied after the first harvest. Annual ryegrass was harvested on 20 February and 19 April 2007 and 20 February and 16 April 2008. Forage was subsequently harvested on 13 June, 10 August, and 13 October 2007 and 11 June, 7 August, and 12 October 2008 for bahiagrass herbage accumulation determination.
Method of establishment affected herbage accumulation of annual ryegrass (Table 1). The glyphosate and prepared seedbed establishment methods resulted in the greatest annual ryegrass herbage accumulation as compared to the other treatments. No differences among control, undisturbed sod, lightly-disked, and the paraquat treatments were observed. The environmental conditions (dry and warm autumn) favored the treatments that decreased the competition between bahiagrass and the newly-established annual ryegrass. The average temperature in November and December 2007 and 2008 was approximately 65oF and the first occurrence of nighttime temperatures below 32oF was 7 February 2007 and 3 January 2008 for years 1 and 2, respectively. In addition, the below-average rainfall during the months of November and December, which coincide with the annual ryegrass establishment months negatively affected establishment and subsequent herbage accumulation.
In addition, there was a significant effect of method of annual ryegrass establishment on the subsequent bahiagrass herbage accumulation (Table 1). The control and overseeding on undisturbed sod treatments had greater bahiagrass herbage accumulation than the glyphosate treatment. There was no difference among the prepared seedbed, paraquat, light-disked, and glyphosate treatments and those treatments did not differ from the control or overseeding on undisturbed sod.
The glyphosate treatment had a greater proportion of common bermudagrass in the stand, followed by the prepared seed (25%), and light disking (12%). There was no difference among the control, undisturbed sod, and paraquat treatments (0%). The greater proportion of common bermudagrass in the glyphosate treatment stand resulted in decreased herbage accumulation when compared to the control and undisturbed sod. Although the light-disked and prepared seedbed treatments had 12% and 25% common bermudagrass, respectively, those levels did not result in decreased the herbage accumulation when compared to the treatments without common bermudagrass in the stand.
In conclusion, the method of establishment affected annual ryegrass herbage accumulation and the herbage accumulation and botanical composition of the subsequent bahiagrass crop. Annual ryegrass herbage accumulation was greater for glyphosate and prepared seedbed treatments because they resulted in greater suppression of bahiagrass growth in the fall, specifically glyphosate and prepared seedbed. However, these two methods of establishment decreased bahiagrass stand in the subsequent growing season and allowed encroachment of common bermudagrass. Although the prepared seedbed treatment resulted in greater encroachment of common bermudagrass, it was the most balanced treatment with greater productions of cool- and warm-season grasses. The glyphosate treatment resulted in greater loss of the bahiagrass stand and decreased herbage accumulation when compared to the control.
Suppressing the bahiagrass sod in the fall is necessary to obtain greater annual ryegrass production, however, the increase in the proportion of undesirable species and decrease in bahiagrass production may require producers to reestablish the bahiagrass stand or cultivate warm-season annual crops to compensate for the decreased bahiagrass production.
Table 1. Herbage accumulation of annual ryegrass broadcast-seeded with different methods of establishment and the subsequent bahiagrass herbage accumulation.
|Treatment||Annual Ryegrass Herbage Accumulation||Bahiagrass Herbage Accumulation|
|- - - - - - - - - - - - - - lb DM/acre - - - - - - - - - - - - -|
|†Means followed by the same lower case letter within columns are not different (P>0.05).|