Establishing Legumes in a Tall Fescue Sward

Tall fescue [Schedonorus arundinaceus (Schreb.) Dumort.] is a common grass species in the eastern half of the USA, but legumes grown with it could provide benefits. Obstacles to legume establishment in fescue pastures include disease, insect damage, and grass competition. Experiments were performed in 2010 and 2011 at Site 1 to test the efficacy of insect control, disease control, and two methods of grass suppression on seedling establishment of three legumes. The highest seedling density of red clover (Trifolium pretense L.) was obtained with glyphosate treatment regardless of pest control and for clipping without pest control. No overall or consistent benefit was found for white clover (Trifolium pretense L.) or trefoil (Lotus corniculatus L.) from seed and foliar insecticides or fungicides, or for grass suppression by either clipping or glyphosate application. Experiments were performed in 2012 and 2013 at Site 2 to test the efficacy of grass suppression by grazing cattle or by clethodim application. Seedling density of red clover was not significantly improved by either treatment, but the density of birdsfoot trefoil was increased by clethodim, and the density of white clover was increased in 2013 by both methods of grass suppression. Overall, red clover was least sensitive to grass competition. Birdsfoot trefoil was better served by the immediate effect of chemical suppression, whereas white clover benefitted most from the lengthier grass suppression provided by grazing.


Introduction
Pastures composed of legumes and grasses benefit from nitrogen (N) transfer from legumes to grasses.Legumes such as alfalfa (Medicago sativa L.) and soybean [Glycine max (L.) Merr.] can provide an annual average of 152 kg and 84 kg N ha −1 , respectively, via symbiotic N fixation [1].Pasture legumes can fix 80 to 110 kg•ha −1 •yr −1 of symbiotic N for companion grasses [2] [3].Legumes grown with grasses also provide a more uniform seasonal distribution of forage than pure cool-season grass pastures because legumes such as alfalfa are less likely to go dormant during mid-summer [4].
Tall fescue [Schedonorus arundinaceus (Schreb.)Dumort.] is one of the most common grass species in the humid transition zone between the temperate North and mild South in the eastern half of the USA [5].It was also one of the most dominant species in complex mixtures with other grasses and legumes at the end of a grazing study in Pennsylvania [6].Maintaining adequate legumes in tall fescue was related to improved animal performance and farm profitability [7].Ladino clover (Trifolium repens L.) interseeded into endophyte-infected tall fescue was more profitable than N-fertilized tall fescue alone [8].In a plot study in southeastern Kansas with multiple legumes, returns from birdsfoot trefoil (Lotus corniculatus L.) were greater than those from alfalfa as well as from red and white clovers [9].
Legume species have differed in their effects on animal performance in fescue pasture.Allen et al. [10] reported that body weight gains of calves grazing stockpiled pastures of alfalfa-tall fescue were greater than those grazing red clover-tall fescue or N-fertilized tall fescue.Ladino clover in endophyte-infected tall fescue also resulted in better average animal gains than red clover or Korean lespedeza [11].
Despite the benefits known to occur from interseeding legumes into tall fescue, procedures have not been developed to the point that managers can incorporate legumes into pastures with any degree of confidence [2].Approaches to improving legume establishment in tall fescue are numerous and include no-till drilling of legumes into tall fescue pasture [11]; controlling grass competition with herbicides [12], mowing, or grazing [13]; limiting N fertilization [14]; and planting pastures with different row orientations [15].Although considerable research has been conducted on legume establishment, little progress has been made to address many of the problems, such as disease, insect damage, heat and/or water stress, and poor seedling vigor [2].The experiments in this study were undertaken to identify and manage the most limiting factors in the complex interactions among diseases, insects, interplant competition, and the environment.

Experiment 1: Pest Control and Grass Suppression
Legume species were interseeded separately into endophyte-infected tall fescue at the Mound Valley Unit of the Kansas State University Southeast Agricultural Research Center (37˚11.5'N,95˚27.4'W).The plot area had been seeded to tall fescue >2 years prior to the test, and had been hayed without benefit of fertilization.The soil was a Parsons silt loam (fine, mixed thermic Mollic Albaqualf) with a pH of 6.3, 7 mg•kg −1 of available P (Mehlich 3), and 128 mg•kg −1 of exchangeable K in the upper 15 cm, to which was added 25 kg/ha of P and 28 kg/ha of K. Spring temperature and precipitation data for the location in 2010 and 2011 are listed in Table 1.
Species were planted with a no-till plot seeder (6 rows with 25-cm spacings, at ~5 mm depth) in 6-m strips, 12 m long in four replications, within a randomized strip split-plot design.Seeding dates for the experiment were April 20, 2010, and April 18, 2011, in adjacent areas.Seeding rates of the species and cultivars provided approximately 250,000 seeds•ha −1 and are listed in Table 2.
The seeded strips of legumes were randomly split into three 2-m subplots, each with six 25-cm rows, to determine the effects of pesticide protection on establishment.Grass suppression treatments (Table 3) were applied in 4-m strips randomly across each replication perpendicular to pesticide treatments, providing individual subplots of 1.5 by 4 m.
Legume seedling counts were taken randomly within a rectangle 33 cm long across the two center rows.In 2010, the rectangle was tossed about midway through the plot length; in 2011, two rectangles were counted at about one-third and two-third of the plot length, respectively.Legume seedling counts were made on June 17, 2010, and June 1, 2011, corresponding to 58 and 50 days after planting (DAP), respectively.
Data were analyzed using PROC MIXED in SAS [16], with replication considered random and all other factors fixed.Fisher's protected LSD was used for multiple comparisons (α = 0.05).

Experiment 2: Grass Suppression by Grazing vs. Chemicals
The same three legume species (Table 2) were mixed and interseeded as previously described into endophyte- In 2012, legume seedling counts were made on June 6, or 100 DAP, and in 2013, counts were taken on June 21, or 98 DAP.Legume seedling counts were taken randomly within a rectangle 76 cm long across the two center rows about midway through the plot length.

Experiment 1: Pest Control and Grass Suppression
Early spring moisture at Mound Valley in 2010 was lower than in 2011 and lower than the long-term average (Table 1).However, legume seedling density did not differ at ≥50 DAP between years, and no interaction between year and any treatment factor was detected, so two-year averages are shown.Legume species differed in seedling density, with red clover density greater (P < 0.05) than that of white clover and alfalfa (data not shown).The relative ability of red clover to establish was typical of most experiments (e.g., Guretzky et al. [14]) owing to the larger seed size of the short-term perennial.
There was a significant (P < 0.01) interaction among the three treatments, so means within legume, pest protection, and fescue suppression treatments are shown in Table 4. Red clover seedling density was initially higher than that of the other legumes (data not shown), but by 50 DAP, seedling density of some red clover treatments was no greater than that of a corresponding treatment of birdsfoot trefoil, and even of white clover when both were untreated.
Red clover seedling density was increased by protection with insecticide only when fescue was not suppressed.Grass suppression by glyphosate increased red clover density except where insecticide was used, and suppression by clipping increased density only when no pest protection was provided.The lack of treatment additivity could indicate some interaction between the legume and effects of the pesticide(s).Seedling density of birdsfoot trefoil and white clover seemed unaffected by pest protection or tall fescue suppression.In contrast, Cuomo et al. [12] found that suppression by glyphosate of cool-season grasses enabled much greater success in obtaining legume stands that included alfalfa, birdsfoot trefoil, red clover, and kura clover (Trifolium ambiguum M. Bieb.).Seguin et al. [13] also found that sod suppression by glyphosate or physical methods contributed to higher red, and particularly white, clover densities.The limited responses to suppression in this experiment may that perhaps grazing should be terminated earlier for red clover than for the other species.Birdsfoot trefoil establishment benefited more from the immediate, temporary effect of chemical treatment than from the more prolonged effects of grazing.This observation is consistent with observations that the species is most sensitive to grass competition at early seedling stages.The fact that white clover establishment was enabled at least as much by grazing as by chemical treatment may indicate that it benefited from the lengthier period of grass suppression provided by grazing and/or was less subject to grazing or treading damage than the other species.
When comparing species, establishment success should be interpreted differently for different species.Populations that could result in productive stands for grazing vary according to species' growth habits.For example, red clover, a biennial with an upright, bunch-type growth habit, may require a higher population to be acceptable than white clover, a perennial that can vegetatively propagate itself by stolons.

Table 1 .
Monthly 30-year temperature and precipitation averages and departures from average for each location-year.

Table 2 .
Legumes and rates (pure, live seed) interseeded into endophyte-infected tall fescue in 2010 and 2011, Mound Valley Unit, Southeast Agricultural Research Center.

Table 3 .
Pesticide protection and fescue suppression treatments to enhance legume establishment in endophyte-infected tall fescue in 2010 and 2011, Mound Valley Unit, Southeast Agricultural Research Center.

Table 1 .
Plots (9.1 by 3.7 m) were seeded as previously described, in separate experiments on February 27, 2012, and March 15, 2013, with the cultivars and the rates listed (Table 2).Suppression treatments were 1) grazing in lieu of clipping, 2) chemical suppression, and 3) an untreated check, randomized in four blocks.Heifers (>225 kg) of primarily Angus breeding were excluded from treatments 2 and 3 with electric fence.Grazed plots were stocked intensively in 2012 from April 12 through May 16.In 2013, plots were grazed from April 22 through May 6 and again from May 17 through 28.Chemical suppression was provided with 0.14 kg/ha of clethodim on March 30 in 2012 and on April 19 in 2013.

Table 4 .
Two-year average seedling density of three legumes interseeded into tall fescue as affected by pest protection and fescue suppression.