Agronomy Gleanings

April 10, 1998
Vol. 98:1

In This Issue:

We are pleased again to be able to share with you a sampling of some the applied research being conducted in our department. Our hope is that you will be able to use this type of research to improve the profitability of your operations and those of the folks you work with. In this years Gleanings we have a sampling of research on some new and old technologies that we think you will find useful. If you have specific questions regarding any of these projects or ideas for new projects please don't hesitate to contact us.

This years Gleanings will again be added to the World Wide Web at our Department of Crop and Soil Sciences Homepage at http://cropsoil.psu.edu/. Look for us there. Have a good year.

Sincerely,

Greg W. Roth
Associate Professor of Agronomy

Using Alfalfa-Grass Mixtures to Minimize Deer Damage

M.H. Hall and R.C. Stout

Alfalfa is a prime feed source for both dairy cows and non-domesticated, white-tailed deer in Pennsylvania. Damage to alfalfa by deer can be great. Numerous attempts have been made to deter deer from feeding on alfalfa and other crops but they have generally proven unsatisfactory because of high costs and/or ineffectiveness. Several researchers have reported that deer prefer alfalfa to forage grasses. However, the use of alfalfa-grass mixtures to deter deer from feeding on forage has been untested.

Study Description

Plots of alfalfa, timothy, orchardgrass, and alfalfa-timothy or orchardgrass mixtures in 3:1, 2:2, and 1:3 alfalfa to grass row arrangements were established within areas protected (with fencing) or unprotected from deer feeding. Forage from these plots was harvested three and four times in 1995 and 1996, respectively, and dry matter yield, percentage of alfalfa and grass, and forage quality were determined. Economic evaluation of each treatment was made based on the value of the harvested forage and the differential costs associated with production.

Applied Questions

To what extent do deer damage forages in central Pennsylvania?

Forages protected from deer feeding averaged 1660 lb/acre more DM yield than their unprotected counterparts (Table 1). The greatest amount of deer feeding occurred in pure alfalfa and the least in pure orchardgrass. Forage quality was not affected by deer grazing. Weeds began to invade the plots in the second year of the study and were more severe in the unprotected than protected plots. Deer feeding resulted in average economic losses of $80 and $28/acre for pure alfalfa and pure orchardgrass, respectively.

Do deer selectively graze one forage species over another?

Deer selectively grazed alfalfa out of the alfalfa-grass mixtures and fed more on plots which contained timothy than those which contained orchardgrass. Averaged across all mixtures, alfalfa made up 35% of the total yield in the protected but only 19% in the unprotected mixed plots. Average yield reductions, as a result of deer feeding, were 1507 and 1102 lb/acre (excluding weed yield in 1996) for treatments containing timothy and orchardgrass, respectively (Table 1). Consequently, the economic losses associated with deer feeding were greater for mixtures containing timothy than orchardgrass (Table 2).

In a field where deer generally feed, are particular forage species or forage mixtures better than others?

In areas unprotected from deer feeding, pure orchardgrass and alfalfa-orchardgrass mixtures had greater total yields than pure alfalfa (Table 2). Weed infestation in the second year of the study was greatest in pure alfalfa which had the greatest deer feeding and least in pure orchardgrass which had the least deer feeding in the first year of the study. Forage quality was not affected by deer feeding within the unprotected plots but was affected by the proportion of alfalfa to grass in the mixture. Alfalfa-orchardgrass mixtures had greater economic returns than pure alfalfa but only when alfalfa was seeded at ≥ 50% of the mixture (Table 2).

Recommendations

Deer feeding can greatly reduce forage yield. Deer selectively grazed alfalfa out of alfalfa-grass mixtures and showed a preference for timothy over orchardgrass. The use of orchardgrass alone or in a mixture with alfalfa minimizes deer feeding and provides the greatest yields. However, when deer feeding occured, net economic returns were greater for alfalfa-orchardgrass mixtures because of improved quality compared to pure orchardgrass.

Table 1. Decrease in dry matter yield associated with deer feeding compared to no deer feeding on pure alfalfa, pure grass, or alfalfa-grass mixtures seeded in different row arrangements (mean of two locations for two years).
Grass species Rows alfalfa:
rows grass 		Reduced yield
alfalfa grass total†
  lb/acre
† Reduction in alfalfa and grass yield combined. Weed yield is not included in total.
---- 4:0 2392 0 2392
Timothy 3:1 2229 154 2384
Timothy 2:2 1272 926 2198
Timothy 1:3 900 822 1722
Timothy 0:4 0 1230 1230
Orchardgrass 3:1 1732 134 1866
Orchardgrass 2:2 1050 568 1617
Orchardgrass 1:3 698 394 1092
Orchardgrass 0:4 0 435 435
Table 2. Increase in dry matter yield and net income of pure grass and alfalfa-grass mixtures seeded in different row arrangements compared to pure alfalfa when both were exposed to deer feeding (mean of two locations for two years).
Grass species Rows alfalfa:
rows grass		 Compared to pure alfalfa
Increased
yield†		 Increased
net return
    lb/acre $/acre
† Includes yield of alfalfa, grass and weeds.
Timothy 3:1 919 11
Timothy 2:2 1556 28
Timothy 1:3 1496 0
Timothy 0:4 1958 -22
Orchardgrass 3:1 2002 41
Orchardgrass 2:2 2844 45
Orchardgrass 1:3 2825 26
Orchardgrass 0:4 3640 6

Production and Persistence of Tall Fescue, Perennial Ryegrass, and Prairie Grass after Fall-Grazing

M.H. Hall, P.J. Levan, E.H. Cash, H.H. Harpster, and S.L. Fales

As the costs associated with animal agriculture increase, so does the interest in grazing to lower feed cost. In Pennsylvania and other temperate environments, extending the grazing season into the fall or early winter further helps reduce animal production expenses relative to feeding hay or silage. Tall fescue has traditionally been the grass species used for fall grazing and/or stockpiling (accumulating standing forage during the growing season for use in late fall or winter). However, other grass species which have excellent fall growth attributes may also work well for fall grazing and/or stockpiling. Our objectives were to evaluate the seasonal and whole-year production of perennial ryegrass, prairie grass, and tall fescue under different fall grazing management schemes.

Study Description

In 1994, 1995 and 1996 three fall-grazing treatments consisting of: 1. Stockpiled; 2. Lax (grazing once in September and then not grazing again until spring); and (3) Intensive (continue grazing on approximately 30 d schedule through November) were imposed on established stands of 'Barcel' tall fescue, 'Citadel' perennial ryegrass, and 'Grasslands Matua' prairie grass at the Haller Livestock and Forage Research Center near State College, PA. Swards were grazed to a residual 2 in. stubble height by mature crossbred (Dorset x Suffolk) ewes. Forage yield, persistence, and ewe grazing days were monitored throughout the study.

Applied Questions

How did Citadel perennial ryegrass perform compared with tall fescue?

Perennial ryegrass and tall fescue responded similarly within and across grazing treatments. Total season yield and persistence of perennial ryegrass were equal to tall fescue regardless of the fall grazing management.

How did Grasslands Matua prairie grass perform compared with tall fescue?

During the first year after implementing the grazing treatments, prairie grass had lower survival and lower total-season yield in the Stockpiled compared with the other grazing treatments. By year two of the study, prairie grass had not survived in any of the grazing treatments. The frequent inability of Grasslands Matua prairie grass to survive Pennsylvania winters makes it an unsuitable grass in perennial pastures.

Which grazing treatment produced the most forage each year?

Continuing to graze grasses on an approximate 30-d interval into the fall until the grasses stopped growing produced the most annual forage and consequently the most grazing days. However, unlike stockpiling, this grazing practice (Intensive) can not extend the grazing beyond November in Pennsylvania. In addition, spring growth of fall grazed and stockpiled grasses is less than when grasses are not harvested after September (Lax). Consequently, a combination of Lax, Intensive and Stockpiled grazing may be the most desirable on farms in Pennsylvania and the Northeast.

Recommendations

Tall fescue and perennial ryegrass were similar in performance regardless of the fall grazing treatment. Grasslands Matua prairie grass did not survive in this and other studies in the northeast region. Therefore, varieties with improved winter survival must be available before farmers in northern climates consider prairie grass as a viable component in perennial pastures. Using a combination of Lax, Intensive and Stockpile grazing may be most desirable. Intensive and Stockpile grazing would allow continued grazing into the fall and early winter, respectively, and Lax grazing would permit early spring grazing while the fall-grazed pastures recover.

Harvest Management Alters Economic Return Cool-Season Grasses

M.H. Hall

Cool-season grass use in Pennsylvania farming systems is increasing as farmers attempt to better manage and utilize nitrogen from manure. Harvest management recommendations for many cool-season grasses are generally based on research which monitored yield only. With forage quality being a major concern in balancing animal rations, livestock farmers are asking more about harvest management practices to manipulate forage quality and the economics of these practices. The objectives of this study were to determine the effect of harvest frequency and number on forage yield and quality, and net economic return of cool-season forage grasses common to the northeastern United States.

Study Description

Established stands of orchardgrass, reed canarygrass, smooth bromegrass, and timothy at the Russell E. Larson Agric. Research Center near Rock Springs, PA were subjected to two (70-d interval), three (45-d interval), or four (35-d interval) harvests per year. Dry matter yield and forage quality were determined and economic evaluations of each treatment were made based on the value of the harvested forage and the differential costs associated with production.

Applied Questions

Which harvest schedule produced the greatest DM yield/acre?

In dry years, greatest DM yields for all species were obtained when 2 or 3 harvests/year where taken on a 70 or 45-d interval, respectively (Table 1). During growing seasons with normal or above normal rainfall, greatest yields of smooth bromegrass and timothy were again achieved when harvested 2 or 3 times/year; however, yields of orchardgrass and reed canarygrass were greatest when harvested 3 or 4 times/year (Table 1).

Which harvest schedule resulted in the highest quality forage?

Regardless of rainfall during the growing season or grass species, forage quality improved and value of the forage increased from $49 to $81/ton as harvest interval decreased from 70 to 35 d, respectively.

Which harvest treatment produced the greatest economic return/acre?

In dry years, the number of harvests (harvest interval) made no difference in net economic return regardless of the grass species (Table 1). This response is logical because harvest schedules that produced the greatest yields also produced forage of the lowest quality, resulting in similar economic return for all harvest schedules.

In growing seasons when rainfall is normal or above normal, frequent harvests (35 or 45-d intervals) tended to result in the greatest net economic return per acre (Table 1). Frequent harvests also produced the highest quality forage but did not negatively impact forage yield as much as in dry years. An exception to this trend was for timothy where harvest frequency had no effect on economic return.

Recommendations

In the northeastern United States, cool-season grass harvest schedules must remain flexible and responsive to climatic conditions. In dry years, reduced yields associated with more frequent harvests of orchardgrass, reed canarygrass, smooth bromegrass and timothy were offset by improved forage quality so that net economic return per acre was unaffected. Therefore, under dry conditions, the level of forage quality required by the consuming animal should be used as guidelines for implementing a harvest schedule. Sufficient DM intake for high producing dairy animals would be impossible with the quality of forage obtained with 70-d harvest intervals. In years when rainfall is at or above normal, 35 to 45-d harvest intervals should be employed to maximize DM yield and forage quality.

Forage producers need to be able to plan a harvest strategy that will maximize net economic return without knowing what the growing season will be like. Consequently, producers who want high quality forage, should plan the first harvest as if four harvests will be taken on 35-d intervals. This means that in central Pennsylvania the first harvest should be taken about 20 May to ensure that a large portion of the grass forage for the season will be of high quality since a large portion of the total annual yield comes in the first harvest. The 35-d harvest interval could then be lengthened to 45 d or more unless rainfall and grass growth are well above normal.

Table 1. The effect of number and frequency of harvests on the annual dry matter (DM) yield and net economic return from four perennial cool-season grasses under different environmental conditions.
Treatments Dry conditions† Normal to wet conditions†
Species Harvest schedule DM Economic return‡ DM Economic return‡
#/yr x interval ton/acre $/acre ton/acre $/acre ton/acre
Orchardgrass 2 x 70 d 3.97§ 88 5.35 159
3 x 45 d 3.77 97 5.64 217
3 x 35 d 3.04 97 ---- --
4 x 35 d ---- -- 5.55 258
Reed canarygrass 2 x 70 d 3.78 96 5.48 197
3 x 45 d 3.63 97 5.86 250
3 x 35 d 2.87 108 ---- --
4 x 35 d ---- -- 5.15 247
Smooth bromegrass 2 x 70 d 4.45 130 6.31 233
3 x 45 d 3.89 117 6.19 283
3 x 35 d 2.77 103 ---- --
4 x 35 d ---- -- 4.89 252
Timothy 2 x 70 d 4.13 106 5.70 172
3 x 45 d 3.70 88 5.25 194
3 x 35 d 2.89 87 ---- --
4 x 35 d ---- -- 4.54 172
† Dry and wet conditions averaged 70 and 135 percent, respectively, of normal (29.6 in. by 1 Oct.). Reduced plant growth permitted only three harvests to be made from the four-harvest treatment in dry years.
‡ Based on relative value of the harvested forage ($65/ton hay with a forage quality of 16% CP and 60% DDM) minus costs for harvesting ($28/harvest) and fertilization.
§ All values are the mean from two years.

Potential of Yield Monitors to Assess Performance in Replicated Strip Trials

Greg Roth, Lynn Hoffman, Elwood Hatley and Mark Antle

Yield monitors are available now to install on most commercial combines. These monitors will make it possible to facilitate agronomic comparisons among many crop input products, including seed corn. The objective of this study was to evaluate the use of a commercial corn yield monitor for conducting hybrid strip tests.

Study Description

A total of six strip tests (three each year) were conducted using six hybrids and three replications in each field during 1996 and 1997. The tests were located on production fields on either local grain farms or on the Penn State agronomy research farm complex. Individual strips were six rows wide and lengths varied from 600 to 1600 feet in length. Hybrids used in the study included: Pioneer brand 3525, Pioneer brand 3527, Dekalb 569, Ciba 4394, NC+3604, Northrup King 6822. In 1997, Northrup King 6800Bt was substituted because seed for 6822 was not available. The strips were harvested with a John Deere 4435 combine equipped with an Ag Leader yield monitor. Each year the yield monitor was calibrated prior to harvesting using field scale loads that were weighed on a certified scale. Each strip was weighed using a weigh wagon that was also calibrated on the research farm's certified scale. Grain moistures were run on certified Motomco moisture meter. The yield monitor was calibrated for grain moisture using the same meter prior to harvesting the study. Errors were calculated using the formula: (Wwyield- Monitor yield)/Wwyield x 100.

Applied Questions

How did the yield monitor predict weigh wagon yields from the strip tests?

In the first year of our study we found errors in 62 strips to range from -9.0 to 22.0% and average 5.8% with a standard deviation of 6.9%. We attributed these errors to variations in grain moisture among hybrids, calibration errors and conditions during harvest. In 1997, with more experience and an updated chip in the Ag Leader yield monitor, we were able to reduce the errors considerably. Yield prediction errors for 58 strips harvested in 1997 ranged from -7.9 to 5.8% and averaged 0.3% (monitor higher than weigh wagon) with a standard deviation of 2.6%. This means that approximately 66% of the time the yield monitor was within 2.6% of the actual yield and that on the average the yield monitor estimate was close to the actual yield.

Figure 1. Yield monitor errors recorded in the 58 strips evaluated in 1997.

figure 1

Were the yield errors due to weight or moisture errors?

Both. Yield errors can be influenced by both grain moisture and weight so careful calibrations are required for both. In our 1997 data, the average error for weights was -1.4% with a standard deviation of 1.9%. For moisture, the average error was 0.6% with a standard deviation of 3.8%. This means that on the average we were closer on the moisture than weight but there were more outliers with moisture. Moisture was a significant source of error in our 1996 studies especially when hybrids with grain moistures above 27% were encountered in the tests. In 1997, the yield monitor appeared to predict these higher moistures much better.

Did the yield monitor errors vary among varieties?

In 1996, the three later varieties in the test had lower yields with the yield monitor because the monitor frequently over predicted the moisture. In 1997, however this did not occur and the yield estimates for the Ag Leader were similar to those from the weigh wagon.

Table 1. Corn hybrid performance averaged over the three fields in Centre County in 1996.
Hybrid Yield Moisture Monitored Yield Monitored Moisture
  bu/A % bu/A %
Pioneer 3525 140.5 22.9 141.1 24.5
Pioneer 3527 146.0 23.0 145.2 24.4
Dekalb 569 136.2 23.9 133.3 24.6
NC+ 3604 140.2 25.0 131.5 26.4
NK 6822 134.4 24.7 125.7 27.4
Ciba 4394 134.6 26.0 122.3 29.7
LSD (0.05) 4.7 1.2 5.0 0.8
Table 2. Corn hybrid performance averaged over the three fields in Centre County in 1997.
Hybrid Yield Moisture Monitored Yield Monitored Moisture
  bu/A % bu/A %
Pioneer 3525 116.4 26.0 115.5 24.8
Pioneer 3527 117.7 24.5 116.6 23.2
Dekalb 569 119.5 27.8 121.5 26.8
NC+ 3604 109.3 24.5 108.4 23.4
NK 6822Bt 128.8 27.5 125.2 26.2
Ciba 4394 104.2 25.8 105.8 24.7
LSD (0.05) 6.9 1.2 5.7 1.3

What factors need to be considered in the use of the yield monitors for strip testing in the our region?

Our experiences with the yield monitor during the past two years support the use recommendations described by others: strips should be long and narrow, grain loads should be at least 4000 pounds, grain moistures should be less than 25%, and the combine should be calibrated well. In our area of central Pennsylvania, smaller field sizes and later maturing corn often result in individual strip test weights that are less than 4000 pounds and may be higher in grain moisture than 25%, however. In 1997, we were successful in achieving reasonable error rates even with these smaller loads and wetter grain. We will continue to test whether smaller loads and wetter corn can be yield monitored accurately with the latest technology. Based on our results in 1997, we feel that yield monitors can be an effective tool for hybrid testing, although individual strip yield errors of more than 5% may be present in some cases.

This research was supported in part from a grant from the Pioneer Crop Management Research Awards Program.

Can Roundup-Ready and Narrow Rows Improve Postemergence Weed Control in Corn?

W. S. Curran, G. W. Roth, E. L. Werner, and D. L. Lingenfelter

With the introduction of Roundup-Ready corn in 1998, the potential exists for better management of some weeds postemergence in corn. In particular, Roundup may offer a greater ability to manage weeds in a total postemergence program in corn. In the past, total post programs in corn have not consistently provided effective control. At the same time, several researcher across the Northeast and corn belt are examining the influence of corn row spacing on weed control and corn yield. In theory, by narrowing the crop row spacing, we can increase the competitiveness and shading ability of the crop and thus improve weed management. A number of studies have demonstrated the weed management benefit of more narrow rows in soybean. However, to date, most of the research in corn suggests that the impact of more narrow rows is variable in terms of improving weed management.

The objective of this research was to compare the performance of several herbicide programs in corn rows spaced 15 and 30 inches apart. Roundup-Ready corn was utilized in this research which allowed the examination of Roundup based postemergence programs.

Study description

An experiment was conducted at the Penn State University Southeastern Field Research and Extension Center near Landisville in 1996 and 1997. Roundup-Ready corn was planted into a conventional seedbed in mid May. Two different hybrids designated as ‘Natalie’ and ‘Jeremy’ were provided by Monsanto in 1996 and 1997, respectively for this study. Commercial hybrids were not available at this time. Corn was planted using a ‘White’ corn planter equipped with splitter units that could provide seven 15 inch or four 30 inch corn rows. Corn was planted at 32,000 plants per acre in the 15 inch rows and 28,000 plants per acre in the 30 inch spacing. Six herbicide treatments were evaluated each season although treatments varied somewhat between the two years (Table 1). In 1997, the Bicep plus Prowl treatment was applied at a ½X rate. Application information including corn and weed growth stage is presented in Table 2. Visual estimates of percent weed control, weed density by species, end of season weed biomass, and corn silage yield were determined for each treatment. The experiment was a randomized complete block design with three replicates in both seasons.

Table 1. Herbicide treatments evaluated in 1996 and 1997.
Herbicide Rate per acre (lb ai per acre) Application time
1996
No herbicide 0 lb -
Bicep 5.9 L + Prowl 3.3 E 3 lb (2 qt) + 0.75 lb (1.8 pt) Pre
Accent 75 DF + Banvel 4 S 0.032 lb (0.66 oz) + 0.25 lb (0.5 pt) Post
Roundup Ultra 4L 0.75 lb (1.5 pt) Post
Roundup Ultra 4L + Harness X 5.6 L 0.75 lb (1.5 pt) + 3.64 lb (2.6 qt) Post
Roundup Ultra fb Roundup Ultra 0.5 (1 pt) fb 0.5 (1 pt) Post fb LPost
1997
No herbicide 0 lb -
Bicep 5.9 L + Prowl 3.3 E 1.5 lb (1 qt) + 0.38 lb (0.6 pt) Pre
Roundup Ultra 4L 0.5 lb (1 pt) Post
Roundup Ultra 4L 1.0 lb (2 pt) Post
Roundup Ultra 4L 0.5 lb (1 pt) LPost
Roundup Ultra 4L 1.0 lb (2 pt) LPost
Table 2. Corn and weed size at application time.
1996
Pre Post LPost
May 23 June 13 June 23
Corn V-4 V-7
Giant foxtail 8 inches -
Velvetleaf 6 inches -
Lambsquarters 6 inches 0.5 inches
Hedge bindweed 12 inches 8 - 12 inches
1997
Pre Post LPost
May 8 June 11 June 19
Corn V-3 V-4
Giant foxtail 4-leaf 4-leaf
Velvetleaf 2 inches 4 inches
Lambsquarters 2 inches 5 inches
Hedge bindweed 3 inches 5 inches

Applied Questions

Did corn grown in 15 inch rows improve the level of weed control compared to 30 inch rows?

Narrowing the corn row from 30 inches to 15 inches did not affect the level of weed control with any herbicide treatment in either 1996 or 1997 (Figures 1 and 2). Most corn is slow to canopy which can promote later emergence of some weeds when a residual herbicide is omitted. However, later emergence of weeds was not a problem in this study. Giant foxtail was the dominant weed both years of the experiment and most giant foxtail emerged prior to the post herbicide applications. The more narrow rows did not reduce weed density nor did it reduce weed biomass.

Some research has shown that narrow row corn may not necessarily reduce weed numbers or even biomass, but it may reduce weed seed production. This is a potential benefit that requires more investigation.

How did the herbicide programs perform in this study?

Weed control was good with most treatments both years of the study. Whether it was a Post Roundup based program or Accent plus Banvel in 1996, weed control was acceptable. No differences occurred between herbicide treatments and only the no herbicide treatment had more weeds (Figure 2). Post application timing can sometimes impact weed control, but in this study, both the Post and LPost Roundup timings in 1997 effectively controlled the weeds. The primary weeds in this study were summer annuals and as mentioned earlier, giant foxtail was the most common weed. Even the ½X rate of Bicep+Prowl provided relatively good weed control in 1997.

Fig. 1 Effect of 6 herbicide treatments on weed biomass in corn, 1996.
Figure 1. Effect of six herbicide treatments on weed biomass in corn, 1996.
fig 2. Effect of 6 herbicide treatments on weed biomass in corn, 1997.
Figure 2. Effect of six herbicide treatments on weed biomass in corn, 1997.

What was the effect of row spacing and herbicide treatment on corn silage yield?

Corn row spacing did not affect corn yield in any treatment. Previous research has shown yield benefits of up to 10% with narrower rows. In 1996, rainfall was plentiful and silage yields were 20 tons per acre or greater in every treatment except the no herbicide treatment (Figure 3). Only the no herbicide treatments yielded significantly less than the herbicide treatments. In 1997, rainfall was more infrequent and silage yields were lower and more variable across herbicide treatments. Corn row spacing again did not affect silage yield in 1997 (Figure 4). Once again, the no herbicide treatment yielded lower than the herbicide treatments, while on average, no difference in yield was observed with any of the herbicide treatments (average over row spacing). Weed control was acceptable and did not affect corn yield except in the absence of an effective herbicide treatment.

Fig 3. Effect of 6 herbicide treatments on corn silage yield in 1996.
Figure 3. Effect of six herbicide treatments on corn silage yield in 1996.
Fig. 4 Effect of 6 herbicide treatments on corn silage yield in 1997.
Figure 4. Effect of six herbicide treatments on corn silage yield in 1997.

Are total postemergence programs effective in corn?

Although this study shows that total postemergence herbicide programs can effectively control weeds in corn, previous experience suggests that the success of single pass programs varies. The success of total post programs will depend on what weeds are present in the field, their severity, proper application timing of the herbicide, a competitive crop to help suppress weeds, and timely rainfall and good soil moisture prior to and following herbicide application. Fields infested with fewer weeds and less late germinating weeds are less likely to require a residual herbicide and are better candidates for total postemergence programs. Late germinating weeds can include pigweed, fall panicum, crabgrass, black nightshade, and common ragweed to name a few. Also, perennial weed problems could limit the success of one pass total post programs. Evaluate each situation to decide whether a total postemergence program is right for you.

Switchgrass Tolerance to Several Corn or Soybean Herbicides

W. S. Curran, J. A. Shaffer, and R. R. Schnabel, and E. L. Werner

Switchgrass (Panicum n L.) is a native warm season perennial grass that has gained popularity in some areas of the U.S. Switchgrass has long been promoted for wildlife habitat and especially for ground nesting birds. More recently, switchgrass has been evaluated in livestock forage production systems, as a source for biofuels, for increasing production on marginal lands, in conservation plantings to control non-point source contaminates, and as a potential native grass in federally funded revegetation projects.

Switchgrass can be slow to establish and a number of factors improve successful establishment. Proper seeding rate, planting depth, planting date, and weed management are all important for successful establishment. Weed management should begin the year before you plan a new seeding by paying particular attention to controlling perennial weeds and reducing seed production of annual weeds.

Grassy weeds are a particular concern to new switchgrass seedings and currently no herbicides are labeled for grassy weed control in switchgrass. Several herbicides might provide selective grass control in new switchgrass seedings, but few studies have evaluated their potential. The objective of this project was to evaluate several Pre and Post applied corn or soybean herbicides with grass activity for switchgrass tolerance. Experiments were conducted in both the field and greenhouse. None of the herbicides evaluated in this research are currently labeled for switchgrass establishment in the northeastern U.S.

Study Descriptions

Field Study. Field experiments were conducted from 1995 through 1997 at the USDA Pasture Research Lab on the Penn State University Russell E. Larson Agricultural Research Farms. ‘Cave-in-Rock’ switchgrass was sown no-till in mid to late April at approximately 10 lb per acre (pure live seed) in a field that was Previously in corn. Roundup (glyphosate) was applied at 1 qt (1 lb ai) per acre after switchgrass seeding and prior to emergence to control any emerged weed species. In addition, 0.5 pint Banvel (0.25 lb ai) per acre was applied to the entire study area in late June for control of broadleaf weeds. In 1995, eight Preemergence and four postemergence herbicide treatments were evaluated (Table 1). In 1996, nine Preemergence (Pre) and six postemergence (Post) treatments were included (Table 1). All Post herbicides except atrazine included a nonionic surfactant at 0.25 % volume/volume. The atrazine treatment included crop oil concentrate at 1% volume per volume. A no herbicide treatment was also included both years. The Pre treatments were applied after planting prior to emergence, while the Post treatments were applied in mid June when the switchgrass had 2 to 3 visible leaves. In the field, switchgrass stand counts were taken the year of establishment and above ground biomass was harvested the year after establishment. The experiment was replicated three times.

Greenhouse Study. Many of the same herbicides evaluated in the field experiment were examined in the greenhouse. Several additional products were also included in the greenhouse experiment and several herbicides was evaluated at two application rates (Table 2). Most herbicides evaluated were either corn or soybean herbicides. Plateau (imazamox) is a product labeled for roadside vegetation management. As in the field, the preemergence treatments were applied immediately after seeding and the postemergence treatments were applied to 2 to 3 leaf stage switchgrass. The same adjuvants were included with the Post treatments as were used in the field study. In the preemergence herbicide study, 15 seed were planted per pot and percent grass emergence was compared with a no-herbicide treatment. In the postemergence experiment, the pots were thinned to 4 to 5 grass plants each prior to herbicide application and both visual estimates of injury and plant biomass were measured 3 weeks after application. The study was repeated.

Table 1. Herbicide treatments evaluated in the field experiment.
Herbicide Rate
lb ai per acre (product/acre)
Pre  
Atrazine 4 L* 1.5 (1.5 qt)
Dual 8 E (metolachlor) 2 (2 pt)
Dual II 7.8 E (metolachlor + safener) 2 (2 pt)
Bicep 6 L (metolachlor + atrazine) 3 (2 qt)
Bicep II 5.9 L (metolachlor + atrazine + safener) 3 (2 qt)
Princep 4 L (simazine) 1.5 (1.5 qt)
Bladex 4 L (cyanazine) 1.5 (1.5 qt)
Atrazine 4L/Princep 4 L (atrazine + simazine) 1+1 (1 + 1 qt)
Atrazine 4 L/Bladex 4 L (atrazine + cyanazine) 1+1 (1 + 1 qt)
Post  
Pursuit 70 DG (imazethapyr) 0.063 (1.44 oz)
Accent 75 DF (nicosulfuron) 0.032 (0.66 oz)
Beacon 75 DF (primisulfuron) 0.036 (0.75 oz)
Basis 75 DF (rimsulfuron + thifensulfuron) 0.016 (0.33 oz)
Raptor 1 S* (imazamox) 0.031 ()
Atrazine 4 L* 1.5 (1.5 qt)
* 1996 only
Table 2 Herbicide treatments evaluated in the greenhouse.
Herbicide Rate lb ai per acre (product/acre)
Pre  
Atrazine 4 L* 1.5 (1.5 qt) and 2 (2 qt)
Bladex 4 L(cyanazine) 1.5 (1.5 qt) and 2 (2 qt)
Princep 4 L (simazine) 1.5 (1.5 qt) and 2 (2 qt)
Atrazine 4 L /Bladex 4 L (atrazine + cyanazine) 1 (1 qt) +1 (1 qt)
Atrazine 4 L/Princep 4L (atrazine + simazine) 1 (1 qt) +1 (1 qt)
Dual II 7.8 E (metolachlor + safener) 1.5 (1.5 pt) and 2 (2 pt)
Dual II 7.8 E + Concept II (metolachlor + safener + safener) 1.5 (1.5 pt) and 2 (2 pt)
MicroTech 4 L(alachlor) 2 (2 qt) and 2.5 (2.5 qt)
Frontier 6 E (dimethenamid) 0.9 (20 oz) and 1.17 (25 oz)
Bicep 6 L (metolachlor + atrazine) 3 (2 qt)
Bicep II 5.9 L (metolachlor + atrazine + safener) 3 (2 qt)
Post  
Atrazine 4L 1.5 (1.5 qt) and 2 (2 qt)
Bladex 90 DF (cyanazine) 1.5 (1.5 qt) and 2 (2.2 lb)
Pursuit 70 DG (imazethapyr) 0.031 (0.72 oz) and 0.063 (1.44 oz)
Accent 75 DF (nicosulfuron) 0.016 (0.33 oz) and 0.032 (0.66 oz)
Beacon 75 DF (primisulfuron) 0.018 (0.378 oz) and 0.036 (0.75 oz)
Basis 75 DF (rimsulfuron + thifensulfuron) 0.008 (0.17 oz) and 0.016 (0.33 oz)
Raptor 1 S (imazamox) 0.018 (2.3 oz) and 0.036 (4.6 oz)
Plateau 2 S (imazameth) 0.031 and 0.063
* 1996 only

Applied Questions

Which treatments provided the most safety to switchgrass in the field experiment?

Across the two establishment years, only the triazine herbicides (Atrazine, Bladex, and Princep) alone or in combination did not significantly reduce switchgrass seedling numbers or grass yield. In the 1995 field study, the hot dry weather along with a variable infestation of some perennial weeds, reduced the success of the switchgrass stand in most treatments including the no herbicide treatment. Switchgrass stand counts in mid summer ranged from 0 plants/m² in the Pursuit treatment to about 70 plants/ m² in the Atrazine/Bladex combination (Table 3). Differences in seedling number and in grass yield were only apparent with the Post treatments in the 1995 seeding with the fewest plants in the no herbicide, Pursuit, and Basis treatments. In particular, weeds reduced switchgrass stand in the no herbicide treatment. Switchgrass yields the year after establishment were lowest in the Pursuit and Beacon treatment (Table 3).

In contrast, the 1996 establishment study had fewer weed problems and ample rainfall. The Pre herbicide treatments containing metolachlor all reduced seedling numbers compared to no herbicide (Table 3). This reduction was also evident in grass yield the year after establishment. In the Post treatments, only Basis reduced seedling numbers compared to no herbicide the year of establishment. However, the year after establishment, Pursuit, Accent, and Basis all reduced grass yield compared with no herbicide (Table 3).

Table 3. Effect of Pre and Post herbicide treatments on switchgrass seedling numbers and grass yield. Seedling counts were taken the year of establishment, while grass yield was measured the year following establishment.
Herbicide 1995 establishment 1996 establishment
Seedling ct. Grass yield Seedling ct. Grass yield
no./m2 g/m2 no./m2 g/m2
Pre        
No herbicide 12 291 139 515
Atrazine - - 212 592
Dual 17 159 11 290
Dual II 21 201 38 134
Bicep 33 347 29 239
Bicep II 28 280 37 224
Princep 14 145 159 476
Bladex 30 288 148 589
Atrazine/Princep 38 224 256 486
Atrazine/Bladex 73 179 166 568
LSD (0.05) NS NS 77 147
Post        
No herbicide 12 291 139 515
Pursuit 0 1 94 332
Accent 67 187 45 352
Beacon 47 77 81 394
Basis 7 242 11 229
Raptor - - 113 431
Atrazine - - 180 440
LSD (0.05) 24 158 97 137

What did the greenhouse experiment show?

Bladex, Princep, and combinations of Atrazine and Bladex or Princep did not reduce switchgrass emergence in the greenhouse (Table 4). All treatments containing a chloroacetamide herbicide (Dual, MicroTech, and Frontier) significantly reduced seedling numbers (Table 4). Within this group of herbicides, seedling numbers were reduced from 36% with MicroTech up to 87% with Frontier. Only slight differences were observed when the rate applied varied (data not presented). Although shoot biomass was also recorded for the Pre treatments, seedling emergence seemed to be a better indicator for predicting herbicide sensitivity. With the Post treatments, all non triazine herbicides reduced switchgrass growth (Table 4). Reductions in growth from these herbicides ranged from 28% with Accent up to 64% with Plateau. Atrazine did not injure the switchgrass. Although several treatments significantly reduced switchgrass growth, none of the Post herbicide treatments killed all of the plants during the 3 week period.

Table 4. Effect of Pre and Post herbicides on switchgrass seedling emergence (Pre) or shoot growth (Post).
Herbicide % reduction relative
to no herbicide
Pre
Atrazine* 26
Bladex 16
Princep 16
Atrazine/Bladex 14
Atrazine/Princep 18
Dual II 67
Dual II + Concept II 73
MicroTech 36
Frontier 87
Bicep 80
Bicep II 64
LSD (0.05) 22
Post
Atrazine* 2
Bladex 22
Pursuit 36
Accent 28
Beacon 40
Basis 42
Raptor 50
Plateau 64
LSD (0.05) 22

What conclusions can be drawn from this research?

Of the Pre herbicides, only the triazines provided adequate safety to seedling switchgrass. The chloroacetamides including Dual, MicroTech, and Frontier reduced seedling numbers and potential grass yield. Safened formulations of metolachlor (Dual II) or metolachlor applied to switchgrass seed treated with Concept II did not provide additional safety. None of the postemergence products except atrazine were completely safe in both the field and greenhouse experiments. In the greenhouse, all Post non triazine products reduced switchgrass growth by a minimum of 28% and as much as 64%. Several of these products also severely reduced growth in the field. Based on these results, none of the non triazine products evaluated in these experiments have adequate safety for use in seedling switchgrass. Finally, none of the herbicides tested in these experiments are currently labeled for use in switchgrass in the Northeast. Therefore, the results of this research are not intended as a recommendation or endorsement for any products.

Row Spacing Effects and Soybean Planting Equipment

John O. Yocum

Row spacing is an important management consideration in soybean production. When we evaluate row spacing research, however, more than just the row spacing needs to be considered. Often wider rows may be planted with a planter rather than a drill and this may lead to different conclusions than if all studies were planted with the same equipment. Two row spacing studies were conducted in 1997 that illustrate this phenomenon.

Study Description

Two soybean management studies were conducted at the Southeast Agricultural Research and Extension Center in Lancaster County during 1997. One study involved row spacing and planting date and was planted using a small plot drill. In this study, the row spacings of 7, 14 and 28 inches were evaluated on May 1 , May 20 and June 10. The second study had 7 inch rows planted with a grain drill and 15 and 30 inch rows planted with a corn planter equipped with splitters. This study was planted on May 14.

Applied Questions

How did soybean yields compare when planted with a grain drill at different row spacings?

The optimum combination of row spacing and planting date was with 7 inch rows planted on May 20. (Table 1) Fourteen inch rows planted on the same date produced 89% of the 7 inch row yield and 28 inch rows produced only 61% of the 7 inch row yield. Wider rows produced yields closer to the 7 inch rows when seeded earlier.

How did soybean yields compare when planted with a grain drill and planter at different row spacings?

In the second study , soybeans seeded with the corn planter in 15 inch rows produced higher yields than those produced in 7 inch rows when seeded with a grain drill. As in the first study 30 inch rows produced the lowest yields but when seeded with a corn planter the yield was 93% of those achieved in 7 inch rows.

What conclusions can be made from these results?

These two studies indicate the problem in recommending a soybean row spacing to produce the best yields. When using the same planting equipment, 7 inch rows produce the best yields. When comparing a unit planter to a drill, however, the unit planter at 15 inches appears to be superior. In both studies the widest rows produced lower yields.

Table 1. Influence of row spacing on soybean yield when seeded with a grain drill, Landisville, 1997.
Date 7 inch 14 inch 28 inch
    Bu/ A  
May 1 55.4 54.6 35.2
May 20 65.2 58.2 39.6
June 10 60.2 55.0 35.2
Table 2. Influence of row spacing on soybean yield when seeded with a grain drill (7 inch rows) or corn planter (15 and 30 inch rows), Landisville, 1997.
Planter/row spacing Soybean yield
  Bu/A
Drill/ 7 inches 66.2
Planter/ 15 inches 69.7
Planter 30 inches 61.3

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