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Agronomy Journal 92:974-980 (2000)
© 2000 American Society of Agronomy

FORAGES

Seasonal Yield Distribution of Cool-Season Grasses following Winter Defoliation

Janet L. Riesterer, Michael D. Casler, Daniel J. Undersander and David K. Combs

Dep. of Agronomy, Univ. of Wisconsin, Madison, WI 53706-1597 USA

jlrieste{at}facstaff.wisc.edu


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 Materials and methods
 NOTES
 Results and discussion
 Summary
 REFERENCES
 
Graziers in southeastern USA often stockpile forage in late summer to extend the grazing season and reduce feeding costs. The effect of winter grazing on the following growing seasons production in the upper Midwest has not been reported. This study was conducted to determine the consequential forage yield and persistence of several cool-season grasses following various winter defoliation and N fertilization treatments in the upper Midwest. Grass cultivars included early and late-maturing orchardgrass (Dactylis glomerata L.), quackgrass [Elytrigia repens (L.) Nevski], reed canarygrass (Phalaris arundinacea L.), smooth bromegrass (Bromus inermis Leyss.), tall fescue (Festuca arundinacea Schreb.), and timothy (Phleum pratense L.). October, December, or March defoliation generally did not affect seasonal forage yield except when early spring growth preceded March defoliation, reducing first-cut forage yields. Without N, timothy, reed canarygrass, and orchardgrass had the highest seasonal forage yields. Both orchardgrass varieties, tall fescue, and reed canarygrass had the greatest response to N whereas timothy had the lowest response. While both spring-applied N treatments (single and split application of 101 kg ha-1) had carryover effects into the midsummer cuttings, the single N application resulted in higher seasonal forage yield than the split-N application. Tall fescue had the greatest carryover response to N in both years. Orchardgrass and reed canarygrass provided the highest forage yields throughout the season. Tall fescue and both orchardgrass varieties were most persistent and timothy, smooth bromegrass, and quackgrass were least persistent.


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
Materials and methods
 NOTES
 Results and discussion
 Summary
 REFERENCES
 
GRAZING COOL-SEASON GRASSES over winter is a management practice used to reduce costs of forage production. Delayed removal of forage after frost may increase spring growth from the added insulation benefits of standing litter. In Canada, King and Van Esbroeck (1991)(p. 65) found that taller stubble of orchardgrass increased snow entrapment and produced a significant level of protection from winterkill. It was visually observed that stockpiling forage increased spring growth in Scotland (Corbett, 1957; Gardner and Hunt, 1955). By dividing a pasture system into early fall, late fall/early winter, and late winter grazing paddocks, spring growth may be managed more efficiently if spring growth rates are staggered by the extended grazing season. Staggering the lush spring growth of forage may abate the need for mechanical harvest of surplus forage.

Seasonal forage yield following winter defoliation has not been studied in the upper Midwest. In Kentucky, Taylor and Templeton (1976) reported no difference in spring yield following October, February, or March grazing of stockpiled tall fescue. Most of the total seasonal growth of cool-season grass occurs in the spring months. As temperatures rise and precipitation decreases, cool-season grasses become dormant, commonly referred to as the summer slump. This poor seasonal growth distribution is a common challenge faced by graziers, forcing them to buy feed or rely on stored forages. If spring yields are distributed over a larger window of time, graziers may be able to manage the growth more easily and utilize the vegetative growth more efficiently. In addition to staggering spring growth by using winter defoliation, strategic applications of N may provide an opportunity to spread spring growth over a longer period of time than is typical of the spring flush.

An objective of this study was to determine the consequential forage yield of seven cool-season grasses following various winter defoliation treatments. Responses to timing and rate of N applications were also studied to learn the effect on spring and seasonal yield distribution of cool-season grasses. Additionally, ground cover ratings of the seven grasses were evaluated to measure persistence following 2 yr of stockpiling.


   Materials and methods
TOP
 ABSTRACT
 INTRODUCTION
 Materials and methods
NOTES
 Results and discussion
 Summary
 REFERENCES
 
Field research was carried out at the University of Wisconsin Agricultural Experiment Stations near Arlington, WI (43°18' N, 89°21' W) and Lancaster, WI (42°50' N, 90°47' W), from 1995 to 1998. The soil types were Plano silt loam (fine-silty, mixed, mesic Typic Argiudoll) at Arlington and Rozetta silt loam (fine-silty, mixed, mesic Typic Hapludalf) at Lancaster. Soil tests at the Arlington site indicated a soil pH near 6.5, organic matter content of 3.9%, P levels at 49 mg kg-1, and K levels at 155 mg kg-1. Lancaster soil tests revealed a slightly higher pH of 6.8, organic matter content of 3.2%, P levels at 28 mg kg-1, and slightly low K levels at 105 mg kg-1.

Seven cool-season cultivars, AC Nordic and Benchmark orchardgrass, Roseau quackgrass, Palaton reed canarygrass, Alpha smooth bromegrass, Barcel tall fescue, and Colt timothy were established at Arlington and Lancaster in the spring of 1995. Grass seed was drilled in seven 15-cm rows within the plot (using a Tool Carrier 2700 Wintersteiger drill, Salt Lake City, UT1) . Plot size was 1.2 by 3.7 m. A border of Martin tall fescue was planted around each plot of quackgrass to reduce the potential of interplot contamination by rhizome spreading (Casler and Goodwin, 1998). At planting and again on 1 August, plots received 67 kg N ha-1 from ammonium nitrate applied with a drop spreader. All stands had nearly 100% ground cover at the beginning of the study.

Four N treatments were imposed (Table 1) . Plots received one of two fertility treatments in late summer, either 0 (F0, control) or 67 [F67(1)] kg N ha-1 on 1 August, which coincided with the start of stockpiling. Two other fertility treatments were applied at the start of stockpiling in late summer and the following spring. The F168(2) treatment was an application of 67 kg N ha-1 on 1 August and 101 kg N ha-1 after the first spring cut (late May). The F168(3) treatment was 67 kg N ha-1 on 1 August and a split application of 45 kg N ha-1 applied before the first spring cut (early April) and 56 kg N ha-1 applied after the first spring cut (Table 1).


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  		Table 1 Rates and schedules of four N fertilization treatments

 
Forage accumulated after 1 August was defoliated by one of three stockpiling treatments during the offseason: (i) just after the first killing frost (mid- to late October), (ii) winter (mid-December), and (iii) late winter (March); these treatments are hereafter referred to as the October, December, and March defoliation dates. Offseason defoliation was done mechanically at Arlington and by grazing at Lancaster. Additionally, a fourth harvest treatment was defined as a control of no stockpiling; this treatment was based on continual harvest throughout the growing season when the tallest plots reached a 30-cm height, leaving no standing forage over winter. The fourth harvest treatment was applied during 1997 only.

The center strip of each plot (90 cm wide) was mechanically harvested with a plot harvester to an 8-cm stubble between mid-May and 1 August as the tallest plots reached a 30-cm height. Only the fourth defoliation treatment was harvested beyond 1 August for the remainder of the growing season. Dry matter determinations were made on grab samples of forage representative of each plot, which was dried in a 55°C forced-air oven. The entire field at Lancaster and Arlington was cut three times in 1997 (Cut 1 = late May; Cut 2 = late June; Cut 3 = late July) and four times in 1998 (Cut 1 = mid-May; Cut 2 = early June; Cut 3 = early July; Cut 4 early August).

Ground cover is defined as the visual rating of the percentage of vegetative tissue of the desired cultivars. Plots were visually rated each spring (early May) to measure ground cover percentage following winter defoliation at Arlington and Lancaster. Additionally, plots were visually rated for ground cover in the fall (early October) at both sites to measure persistence. Persistence is defined as maintenance of ground cover at the end of the study (Casler and Goodwin, 1998; Casler, 1988). Ground cover data were not normally distributed so were transformed with the arcsin-square root function.

The experimental design was a randomized complete block with four replicates and a restricted randomization: a split-plot within a strip-plot (Fig. 1) . The two whole-plot factors were offseason defoliation dates and fertility treatments, randomized and stripped across each other within each complete block; subplots were combinations of offseason defoliation dates by fertility treatments; and sub-subplots were the seven cultivars. Forage yield and groundcover percentage were analyzed separately for each site due to different winter defoliation methods. Data at each site were analyzed with an ANOVA model consisting of winter defoliation date, fertility treatment, cultivar, and year, all of which were fixed effects, and replicates as random effects. Data are presented on the original, nontransformed scale. Comparison between means were made using Fisher's LSD at P < 0.05.



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  		Fig. 1 Field layout of one block in the experimental design: a split plot within a strip plot. Harvest date whole plots (vertical lines) and fertilizer treatment whole plots (horizontal lines), are randomized within the block. Sub-subplots are grasses: 1 = orchardgrass, late; 2 = orchardgrass, early; 3 = quackgrass; 4 = reed canarygrass; 5 = smooth bromegrass; 6 = tall fescue; 7 = timothy. F0 = no N; F168(2) = 67 kg N ha-1 previous August, 101 kg N ha-1 after Cut 1; F168(3) = 67 kg N ha-1 previous August, 45 kg N ha-1 before Cut 1 and 56 kg N ha-1 after Cut 1

 

   Results and discussion
TOP
 ABSTRACT
 INTRODUCTION
 Materials and methods
 NOTES
 Results and discussion
Summary
 REFERENCES
 
Spring Ground Cover
Ground cover in early May was not affected by fall or winter defoliation dates (October, December, March) at Arlington in either year (Table 2) . For Lancaster in 1997, December defoliation reduced spring ground cover by 9% compared with October defoliation but there was no difference between March and October defoliation. For Lancaster in 1998, ground cover on the nonstockpiled defoliation treatment was 12.5% higher than March defoliation and 6% higher than the average of October and December. The March defoliation date may have included some early growth at Lancaster in 1998, thereby delaying growth in April relative to the other defoliation treatments. Higher ground cover percentages for the nonstockpiled treatment may be due to differences in cutting management; the three stockpiled treatments were harvested in mid-May, late June, and late-July of 1997. The nonstockpiled treatment was harvested in mid-May, late June, and early September. Plants may have benefited from the longer rest period on the nonstockpiled treatment and had more time to store carbohydrate in the stem bases and roots before being harvested.


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  		Table 2 Mean ground cover in early May of 1997 and 1998 following each of four defoliation treatments at Arlington, WI, and Lancaster, WI. Means are averaged over four N treatments, seven grasses, and four replicates

 
Ground cover response to N varied over sites and years, but generally, N fertilizer improved ground cover (Table 3) . Ground cover ratings were highest for the early spring N application [F168(3)] and lowest for the control (F0) at both sites in 1997. Ground cover was higher with N applied the previous summer [F67(1) and F168(2)] than no N at Arlington but not at Lancaster, 1997. Similar to results from Lancaster, ground cover was not affected by a late summer application of 80 kg N ha-1 in Wales (Skinner and Allen, 1991). There were no N treatment effects on ground cover at Arlington in 1998. However, ground cover was unexpectedly 4% lower on F168(3) than F0 in 1998 at Lancaster.


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  		Table 3 Mean ground cover in early May of 1997 and 1998 of winter-defoliated forage on four N treatments at Arlington, WI, and Lancaster, WI. Means are averaged over seven grasses, four winter defoliation treatments, and four replicates

 
Cultivar rankings for spring ground cover were generally consistent across sites with the exception of timothy and late-maturing orchardgrass (Table 4) . Because there were no year x cultivar interactions, cultivar means are presented as means over years. Late-maturing orchardgrass had one of the lowest ground cover percentages at Arlington, while timothy had the lowest ground cover at Lancaster. Timothy may have been damaged by close grazing and/or hoof damage at Lancaster. All other cultivars ranked in the same order at each site, and quackgrass and smooth bromegrass invariably ranked higher in ground cover than all other cultivars.


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  		Table 4 Mean ground cover in early May of 1997 and 1998 of seven winter-defoliated grasses at Arlington, WI, and Lancaster, WI. Means are averaged over four winter defoliation treatments, four N treatments, 2 yr, and four replicates

 
Forage Yield
Winter Defoliation Effects
Spring forage yield was not affected by fall or winter defoliation date at Arlington in either year but was affected by defoliation date and year at Lancaster (Table 5) . March defoliation reduced spring forage yield at Lancaster by 36 and 76% in 1997 and 1998, respectively, compared with the average of the other defoliation treatments. Early spring growth was observed in mid-March of 1998 from unusually mild temperatures and accompanying rain. It is likely that early growth was harvested as part of the March defoliation date, reducing the total growth measured in May. Additionally, grazing in late March, when ground conditions are conducive to hoof damage, may have a deleterious effect on plant persistence.


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  		Table 5 Mean spring and summer forage yield in 1997 and 1998 for cool-season grass on four winter defoliation treatments at Arlington, WI, and Lancaster, WI. Means are averaged over four N treatments, seven grasses and four replicates

 
The nonstockpiled treatment and December defoliation had similar forage yields at Lancaster in the spring of 1998. Both defoliation treatments yielded 25% higher than the October defoliation date. Similarly, a nonstockpiled defoliation treatment of a grass–clover (Trifolium spp.) sward yielded 24% higher on the first spring cut than a late October defoliation (Frankow-Lindberg et al., 1997). In Kentucky, a nonstockpiled defoliation treatment had the highest forage yield on the first spring cut followed by October, February, and March defoliation, with the lowest forage yield observed following November and December defoliation dates (Taylor and Templeton, 1976).

Total summer forage yield was not affected by fall or winter defoliation dates at Arlington in either year or Lancaster in 1997 (Table 5). Similarly, September defoliation or both September and October defoliation in Sweden (Frankow-Lindberg et al., 1997) and either December or January defoliation in West Virginia (Balasko, 1977) did not affect summer forage yield. December defoliation at Lancaster increased total summer forage yield by 15.3 and 8.6% over October defoliation and the nonstockpiled treatment, respectively, in 1998. However, March defoliation reduced total summer forage yield by 30.9% compared with the average of the other fall and winter defoliation dates at Lancaster in 1998. March defoliation at Lancaster in 1998 not only reduced spring forage yield but also likely contributed to overall reductions in total summer forage yield.

Cultivar rankings for spring forage yield were generally consistent following the winter defoliation dates (Table 6) . There was no year x cultivar interaction, so years were averaged. Reed canarygrass, early maturing orchardgrass, and smooth bromegrass ranked highest in spring forage yield following all winter defoliation dates at both sites; smooth bromegrass following the March defoliation at Lancaster was the only exception to this. Reed canarygrass, smooth bromegrass, and timothy are very winterhardy grasses, which likely contribute to high spring yields, while the morphological characteristics of early maturing orchardgrass produce high spring yields. Spring forage yield of all cultivars was depressed following the March defoliation at Lancaster. March defoliation reduced the 1998 spring forage yields of smooth bromegrass and quackgrass an average of 60% compared with December defoliation at Lancaster. Smooth bromegrass was reported to produce >30% of its seasonal production in the first 12 wk after initiation of spring growth, with the majority occurring within the first month (Moore et al., 1991). Similarly high growth rates of smooth bromegrass likely occurred in our study. Ground cover percentages reflected early spring growth for smooth bromegrass and quackgrass while low spring forage yields suggested some early growth was included as part of the March defoliation. Quackgrass consistently ranked lowest in forage yield at both sites and years. Defoliation at different times during fall or winter generally did not affect spring forage yield for most cultivars if it was accomplished before the onset of spring growth.


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  		Table 6 Mean spring forage yield of seven cool-season grasses following three winter defoliation treatments at Arlington, WI, and Lancaster, WI. Means are averaged over four N treatments, 2 yr, and four replicates

 
Cultivar rankings for total summer forage yield were similar to those for spring forage yield ,with the exception that smooth bromegrass ranked lower than timothy and late-maturing orchardgrass at Lancaster and Arlington (data not shown). Smooth bromegrass normally produces the majority of its seasonal growth in early spring when leaf area, light interception, and therefore growth rate are at a maximum and production declines during the summer when these factors are reduced (Engel et al., 1987). Early maturing orchardgrass consistently had the highest forage yield, followed by reed canarygrass, late-maturing orchardgrass, and timothy at Arlington. Tall fescue and reed canarygrass had the highest forage yield, followed by both orchardgrass varieties at Lancaster. At both sites, quackgrass had the lowest forage yield. Conversely, the 4-yr mean forage yield of quackgrass was similar to forage yield of reed canarygrass and smooth bromegrass under a three- and four-cut schedule in both northern and southern Minnesota (Sheaffer et al., 1990). Ecotype differences between our study and the Minnesota study may explain the inconsistent results. It is more likely that Roseau ecotype of quackgrass is not well adapted to Wisconsin, as Roseau seed originated from northern Minnesota.

Nitrogen Treatment Effects
Nitrogen fertilizer (67 kg N ha-1) applied in late summer had little or no effect on Cut 1 of the following year for any site–year combination averaged across cultivars (Fig. 2) . However, higher levels of N fertilizer (112 kg N ha-1) applied in late summer substantially increased first-cut forage yield of smooth bromegrass in Quebec (Look-Kin and MacKenzie, 1970). Application of 45 kg N ha-1 in early April [F168(3)] had little effect on Cut 1 in 1997 but it nearly doubled the forage yield of Cut 1 in 1998 at each site compared with no N fertilizer. Ample rainfall and above average temperatures in the spring of 1998 contributed to substantially higher forage yield. Rainfall in 1997 was below normal until June, which then stimulated grass growth after the first cut.



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  		Fig. 2 Seasonal yield distribution of cool-season grass on four N treatments at Arlington (ARL) and Lancaster, (LAN), WI, in 1997 and 1998 cut three or four times. Means are averaged over seven grasses, four winter defoliation treatments, and four replicates. F0 = no N; F67(1) = 67 kg N ha-1 previous August; F168(2) = 67 kg N ha-1 previous August, and 101 kg N ha-1 after Cut 1; F168(3) = 67 kg N ha-1 previous August, 45 kg N ha-1 before Cut 1, and 56 kg N ha-1 after Cut 1. LSD(0.05) = 0.09 and 0.13 at Arlington and Lancaster, respectively

 
Second-cut forage yield on the split and one-time N applications [F168(3) and F168(2), respectively] was 125 and 185% higher, respectively, than on the late-summer N treatment [F67(1)] and the unfertilized treatment, and remained higher throughout most of the growing season at all site–year combinations. Similarly, summer forage yield of cool-season grasses increased 66% with spring-applied N compared with no added N (Narasimhalu et al., 1981). Addition of 101 kg N ha-1 after the first cut increased forage yield of Cut 2 an average of 1.30 Mg ha-1 compared with no N, across sites and years. The split N treatment more than doubled forage yield of Cut 2 vs. no N across sites and years. The increased second-cut forage yield could have been a combination of the added 56 kg N ha-1 applied after Cut 1 and some carryover of the 45 kg N ha-1 applied before Cut 1. Carryover of N was more likely in 1997 when there was little N response on first-cut forage yield. In 1998, increased second-cut forage yield is more likely a response to 56 kg N ha-1 added after Cut 1.

Seasonal forage yield was slightly higher (20%) for the one-time N application than for the split-N application across sites in 1997. Cool, dry conditions in the spring of 1997 reduced the effectiveness of the 45 kg N ha-1 applied before Cut 1. Smaller differences were measured between the one-time N application and the split application in 1998 due to a greater yield response to N applied before Cut 1 for all cultivars. Furthermore, 101 kg N ha-1 applied after Cut 1 also increased forage yield of Cut 3 more so than the split N application at both sites in 1998. A one-time N application vs. a split-N application is recommended in the spring after Cut 1 when temperature and soil water are optimal for grass growth. The one-time N application of 101 kg N ha-1 is more economical than the split-N application in both reduced costs associated with N application and increased forage yield in midsummer when typical low forage yield must be supplemented with expensive stored feed.

Smooth bromegrass, reed canarygrass, and early maturing orchardgrass consistently ranked at the top in first-cut forage yields in dry or wet conditions, across all N treatments (Fig. 3) . The bulk of the seasonal forage yield of these same species in New Jersey, with N rates up to 112 kg N ha -1 applied in early April, occurred in the first two cuttings before soil water became limiting (Duell, 1960).



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  		Fig. 3 Mean seasonal forage yield of seven cool-season grasses on three N treatments cut three or four times at Arlington and Lancaster in 1997 and 1998. Means are averaged over four winter defoliation treatments and four replicates. 1 = orchardgrass, late; 2 = orchardgrass, early; 3 = quackgrass; 4 = reed canarygrass; 5 = smooth bromegrass; 6 = tall fescue; 7 = timothy. F0 = no N; F168(2) = 67 kg N ha-1 previous August, 101 kg N ha-1 after Cut 1; F168(3) = 67 kg N ha-1 previous August, 45 kg N ha-1 before Cut 1 and 56 kg N ha-1 after Cut 1. LSD(0.05) = 0.25 and 0.17 at Lancaster and Arlington, respectively

 
First cut yield of unfertilized forage was low at both sites in the cool, dry spring of 1997, resulting in a fairly even seasonal forage yield distribution of all cultivars except timothy. Above average rainfall and warm temperatures in 1998 resulted in nearly 50% of the seasonal forage yield for early maturing orchardgrass, reed canarygrass, and smooth bromegrass in Cut 1 while seasonal yield remained fairly level for quackgrass, tall fescue, and timothy on the F0 treatment at Lancaster. Despite the increased forage yield in 1998, total seasonal forage yield of unfertilized grass averaged <2.8 Mg DM ha-1 across cultivars and sites.

Timothy consistently ranked first in total forage yield under no N fertilization for all site–year combinations (Fig. 3). In northern Wisconsin, timothy yielded higher than smooth bromegrass and orchardgrass without N fertilization (Schmidt and Tenpas, 1960). More than half of the seasonal growth of timothy occurred by second cut across years. Likewise, in other studies, timothy has been shown to produce more of its seasonal yield in June during primary growth (Cooper, 1958; Kunelius and McRae, 1986). Seasonal forage yield distribution of the two orchardgrass varieties was dependent on their relative maturity. The early maturing orchardgrass had a higher percentage of total growth in first cut, while the late-maturing orchardgrass had a higher percentage of total growth in second cut. The relatively high seasonal yield of unfertilized timothy, both orchardgrass varieties, and reed canarygrass make these cultivars desirable to seed in situations where rainfall events are infrequent or where N is very expensive. Forage yield results from the F67(1) fertilizer treatment were generally the same as those from F0; therefore, this data was not presented.

Orchardgrass and reed canarygrass generally had the highest seasonal forage yields on both spring-applied N treatments with second-cut forage yield increases averaging 235% vs. no N. Strong linear relationships between N level and increased forage yield were observed with up to 672 kg N ha-1 for reed canarygrass (Dean and Clark, 1972) and up to 560 kg N ha-1 for orchardgrass (Mortensen et al., 1964). Higher N uptake of reed canarygrass and orchardgrass relative to other cultivars contributes to their high forage yields (Marten et al., 1979).

Seasonal forage yield more than doubled with the application of 101 kg N ha-1 after Cut 1 [F168(2)] compared with no N for all grasses except timothy at Arlington and Lancaster in both years (Fig. 3). Seasonal forage yield of timothy increased <60% on F168(2) at each site and in each year. A study in British Columbia comparing timothy and reed canarygrass reported a relatively low response of timothy to spring-applied N; reed canarygrass forage yield increased fivefold, while timothy forage yield increased twofold (Kline and Broersma, 1983). Total root mass of timothy was 40 to 50% lower compared with orchardgrass and smooth bromegrass, which contributes to low N response of timothy (Gist and Smith, 1948).

Nitrogen carryover from the F168(2) N treatment to third-cut was most evident for tall fescue, which more than doubled in forage yield, compared with no N at both sites and years. High third-cut forage yield for tall fescue is due to a combination of carryover N and growth characteristics, which respond well to high temperatures and low rainfall of midsummer. Late-maturing orchardgrass, reed canarygrass, and timothy had the lowest N carryover to the third cut in both years and sites. Most of the N response of late-maturing orchardgrass and timothy occurred in Cut 2 and most of the applied N was likely used to produce second-cut forage.

All grasses had higher or equal seasonal forage yield on the one-time N application than the split N application for all site–year combinations.

Fall Ground Cover
Fall ground cover in early October was not affected by winter defoliation treatment at either site or year (data not shown). There was no year x N treatment interaction; hence, years were averaged. Nitrogen fertilizer improved fall ground cover at both sites (Table 7) . Mean fall ground cover of fertilized plots increased 6% at Arlington and Lancaster compared with unfertilized plots. Spring-applied N treatments [F168(2) and F168(3)] were generally higher in ground cover than the fall-applied N treatment [F67(1)] at both sites.


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  		Table 7 Mean fall ground cover percentage of cool-season grass on four N treatments at Arlington, WI, and Lancaster, WI. Means are averaged over seven grasses, four winter defoliation treatments, 2 yr, and four replicates

 
Fall ground cover of each cultivar ranked similarly across sites (Table 8) . Tall fescue and both orchardgrass varieties consistently had the highest fall ground cover percentages at both sites while quackgrass, smooth bromegrass, and timothy had the lowest ground cover. The seasonal cutting frequency was determined when the height of the tallest grass reached 30 cm, which was likely detrimental to some grasses during their regrowth cycles. In regrowth, orchardgrass and tall fescue have culmless vegetative shoots while smooth bromegrass and timothy have culmed vegetative shoots, i.e., internodes of smooth bromegrass and timothy continue to elongate in regrowth cycles. Regrowth of smooth bromegrass and timothy must come from new tillers, whereas growth can continue from existing tillers in orchardgrass and tall fescue. Low carbohydrate reserves and lower tiller bud density of smooth bromegrass and timothy contributed to slower regrowth (Reynolds and Smith, 1962). Marten and Hovin (1980) found it difficult to maintain smooth bromegrass in Minnesota on a three-cut schedule when it was cut below 8 cm during stem elongation, due to removal of shoot apices and tillers.


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  		Table 8 Mean fall ground cover percentage of seven cool-season grasses at Arlington, WI, and Lancaster, WI. Means are averaged over four N treatments, four winter defoliation treatments, 2 yr, and four replicates

 

   Summary
TOP
 ABSTRACT
 INTRODUCTION
 Materials and methods
 NOTES
 Results and discussion
 Summary
REFERENCES
 
Winter grazing or clipping does not affect spring ground cover or spring forage yield if it was accomplished before spring growth. Likewise, total-season forage yield was not affected by winter defoliation. Tall fescue and both orchardgrass varieties are best suited for season-long growth. Quackgrass consistently yielded the lowest and the present ecotype seems to be poorly adapted to Wisconsin. Fall ground cover ratings indicated that smooth bromegrass, timothy, and quackgrass were the least persistent while tall fescue and both orchardgrass varieties were most persistent. Therefore, smooth bromegrass and timothy should be seeded separately from orchardgrass or tall fescue so that each can be managed effectively.

Nitrogen fertilization improved both spring and fall ground cover percentages. The N effect on spring forage yield was dependent on climatic conditions: there was little to no spring-N response when rainfall and temperatures were below normal. Application of 101 kg N ha-1 after first cut was more effective than a split application of 45 kg N ha-1 before first cut and 56 kg N ha-1 after first cut. Addition of 101 kg N ha-1 should be made in late spring when available soil water is optimal. Both orchardgrass varieties and reed canarygrass had the greatest response to applied N, and timothy had the lowest response to N. Nitrogen carryover was greatest for tall fescue, which maintained fairly uniform forage yields during the season. Tall fescue in Wisconsin did not go into a summer slump similar to its growth habit in the southern USA. Without N, timothy, early maturing orchardgrass, and reed canarygrass had the highest forage yields, which make planting these cultivars appropriate in situations where rainfall is limited or N is expensive.


   NOTES
TOP
 ABSTRACT
 INTRODUCTION
 Materials and methods
 NOTES
Results and discussion
 Summary
 REFERENCES
 
1 Trade names are for the readers convenience and do not imply endorsement by the University of Wisconsin. Back

Received for publication May 24, 1999.
   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 Materials and methods
 NOTES
 Results and discussion
 Summary
 REFERENCES
 




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R. Leep, P. Jeranyama, D.-H. Min, T. Dietz, S. Bughrara, and J. Isleib
Grazing Effects on Herbage Mass and Composition in Grass-Birdsfoot Trefoil Mixtures
Agron. J., November 1, 2002; 94(6): 1257 - 1262.
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