Volume 25, Number 2, May 2001

elcome to the Spring 2001 Forager. What a long winter; much different than the last three. Alfalfa seems to have come through in good shape with the exception of low areas where ice sheeting occurred. In addition, some pasture grasses were affected. See the accompanying article for more information. Some late frosts set back plants in some areas, but did not appear to have a significant impact. Make sure to get out and scout fields for winter injury.

We are looking forward to the Tri-State Hay show in June at the Arlington Research Station. Every three years we hold our WFC Expo in conjunction with this event. The American Forage and Grassland Council held it’s annual meeting in Arkansas recently. Included in this issue are two timely articles from the proceedings of this meeting. In addition, there is information on the impact of wheel traffic in alfalfa and more.

In This Issue:

Many farmers have seen wheel tracks in fields that were harvested too wet and the alfalfa killed out. This is an extreme example of wheel traffic effect during harvesting on alfalfa yield, lesser effects likely occur in many years but remain unnoticed. Some previous work in Wisconsin and in California indicated a yield reduction in alfalfa due to wheel traffic on alfalfa. The Wisconsin studies were yield reductions from wheel traffic applied prior planting while the California research simulated wheel traffic after cutting in an established stand. We began a program to evaluate the effect of wheel traffic after cutting on alfalfa.

Studies were established at the UW Arlington Research Station and ABI Research Station (Napier, IA) during the spring of 2000. Twenty alfalfa varieties/experimental lines were seeded in small plots. First cutting on all plots within a site were taken on June 18 at Napier, IA and on July 18, at Arlington, WI. Wheel traffic was applied five days after cutting by driving approximately a 94 Hp tractor (with 18-inch wide rear wheels and weighing approximately 8,400 lbs) across the plots covering the entire plots with both wheel tracks. This was repeated three times so that wheel traffic plots received six wheel tracks to simulate driving over the field with tractor, chopper and wagons, or tractor, baler and wagon. After first cutting, some plots were cut every 21 days and some every 35 days.

Yield reductions due to wheel traffic are shown in the Table 1. No yield reduction occurred on first cutting because wheel traffic was not applied until after first cutting. The yield reductions due to wheel traffic on later cuttings were astounding. Wheel traffic reduced yield to 12 to 70 percent compared with no wheel traffic, depending on the cutting and location. The plots at Napier generally had lower yields, and therefore less yield reductions, because of dryer conditions most of the season. We think the yield reduction due to wheel traffic will be greater on wet soils.

While all alfalfa varieties showed some yield reduction due to wheel traffic, some entries were less affected than others. Some varieties yielded over one t/a less for the season with wheel traffic compared to no wheel traffic, while others showed only a five percent reduction. Since this trait appears to be so greatly affected by environmental conditions, we feel that we need another year’s data before we release varietal information.

Yield reductions due to wheel traffic can be related to physical damage to the soil and plant. Deep soil compaction is related to axel weight, and surface soil compaction is related to contact weight (weight per surface area of wheel contact with soil). Wheel compaction usually only occurs on heavier soils. Wheel traffic damage to alfalfa crowns may result in cracking or breakage of the crown, which will reduce the shoots produced and may allow entry of disease. In five days, shoots will have begun to regrow and if they are broken by wheel traffic, this will result in a yield reduction.

The amount of wheel traffic yield reduction is likely going to vary from field to field and cutting to cutting depending on plant and soil conditions. In retrospect, it is likely that we increased wheel damage by waiting five days to apply it rather than applying it sooner. This means that chopping for silage one day after mowing may cause less yield reduction than bailing four to five days after mowing. We will be testing this during 2001. We also do not know whether it is better to drive in the same tracks as much as possible to spread the wheel traffic out over the field.

What can be done? While selection for traffic tolerant varieties is going on and will improve yields of alfalfa over time, there are management practices minimizing field traffic that can likely reduce the impact of wheel traffic now. These are as follows:

1) Use small tractors when possible, the larger tractors may have the air-conditioned cab and better radio, but will likely cause more soil compaction than lighter tractors.

2) Avoid unnecessary trips across the field when harvesting.

· By mowing and conditioning in a single operation.

· Driving full wagons on a road or path rather than the length of the field?

· Accumulating dropped bales with least possible driving?

· Avoid driving on alfalfa field when harvesting crop of adjacent field.

3) Consider using larger equipment (there is some question about this because while less area is affected by wheel traffic, the affected area has greater weight applied to it). This could be another benefit of contract harvesting.

4) Drive on field as soon after cutting is possible (e.g. make silage from higher yielding fields, hay from lower yielding fields).

Table 1. Alfalfa yield reduction due to wheel traffic in seeding year at Arlington, WI and Napier, IA during 2000.

Days between -------------% Yield Reduction-----------

Site cuttings Cut 2 Cut 3 Cut 4 Total¹

Arlington, WI 21 51.0 51.7 73.1 37.0

Napier, IA 21 69.9 46.0 12.3 19.7

Arlington, WI 35 19.2 29.1 -- 12.6

Napier, IA 35 61.8 50.4 -- 31.1

¹ including first cutting which had no wheel traffic or yield reduction due to wheel traffic

Sponsorship Opportunities

The Wisconsin Forage Council is looking for companies to sponsor up-coming issues of The Forager. The Forager is a quarterly newsletter that is mailed to all WFC members. Membership includes forage producers and university and industry personnel all over the United States and Canada. The cost of sponsorship is $500 for a full-page ad, $250 for a half-page ad and $175 for a quarter-page ad. These sponsorships help cover the cost of printing and mailing The Forager allowing money to be available to put towards other projects. This is an excellent way to reach a specific target audience with interest in forage production. If you are interested in sponsoring an issue, please contact Shelly Minick at the WFC office at 608-846-1825 for more information.

The following are excepts of two articles that were in the American Forage and Grassland Council proceedings of the Annual Symposium held April 22-25, 2001 in Springfield, Arkansas.

Effects Of Seeding Rate On Plant Thinning And Crown Development Of Alfalfa

C.J. Nelson, M.H. Hall, R.L. Kallenbach, and J.H. Coutts

University of Missouri and Pennsylvania State University

Yield is largely independent from seeding rate if 6 lbs/acre or more pure live seed are planted. Generally, number of emerged seedlings is directly proportional to seeding rate, but other factors such as seedbed condition, seeding method, and rainfall after seeding also affect initial stand. During the 18-24 months after a spring seeding, stands self-thin rapidly, largely due to high plant competition. This response is associated with an increase in shoots/plant, especially at low seeding rates.

In several experiments the reduction in plant density was most rapid at high seeding rates, but after 2-4 years, the stand density, i.e. plants/sq ft, was still greater for the high seeding rate. Further, the number of shoots/plants was proportionately less, such that number of shoots/sq ft was similar over a range of seeding rates. These data indicate that stands established with high seeding rates will have more, but smaller and perhaps less vigorous plants during the production years, which may later survival of individual plants.

In these studies alfalfa was seeded on a tilled seedbed about Apr 1, 1994, 1995, 1997, and 1998 at rates of 3, 6, 9, 15, and 22 lbs pure live seed/acre. Three varieties (Alfagraze, Pioneer 5373 and Cody) were used. Plots were harvested 4 times during the seeding year. There were very few seeding rate interactions. Thus data presented are means of the three cultivars.

Annual yields for the seeding year were similar at all seeding rates except for reduced yield at 3 lbs/acre, a trend that continued through subsequent production years. The need for weed control in later years was greatest at the 3 lb seeding rate, and to a lesser extent at the 6 lb rate. Emergence of seedlings and initial stand density at 1 or 3 months after seeding varied with year-to-year environmental conditions but were proportional to seeding rate. In all cases the stand thinned quickly to about 6 plants/sq ft, after which it thinned at a much slower rate. Plant density remained proportional to seeding rate as the stand thinned, which contrasts normal theory as stands should thin rapidly, but at different rates to reach the same density.

As plant density decreased with time the number of shoots/plant increased. From about 26 months after seeding until the end of the experiments, the relationship between shoots/plant and plant density was near linear eventually reaching a maximum for 15 additional shoots/plant for each loss of 1 plant/sq ft.

It appears that shoots/plant is a reaction to loss of adjacent plants, probably a response to more light reaching to the crown level in thinner stands. At low seeding rates, however, buds and new crown shoots were competing for light with developing weeds. Weeds that are not controlled may shade the crown area which reduces development and survival of new shoots. This further reduces the competitiveness and yield potential of remaining plants because shoots/sq ft is reduced below the threshold for maximum yield. Since crown development is an explorative process, and weed control is a major factor in long-term persistence of alfalfa, high seeding rates may be beneficial.

Editors note: The following mentions some grasses not commonly grown in Wisconsin, but we believe the principles apply. Correct seeding depth of grasses is critical to getting a good stand. We recommend seeding no deeper than 1 inch.

Seeding vigor and depth of planting directly affect the success of establishing a cool season perennial grass. The objective of this study was to evaluate the effect of different planting depths on selected cool season perennial grasses. The trial was conducted in the fall of 2000 at the Nobel Foundation Headquarters Farm in Ardmore, Oklahoma inside a non-climate controlled hoop house. Raised beds were constructed of treated lumber and filled with sandy loam topsoil. ‘Barton’ western wheatgrass, ‘Kentucky 31’ tall fescue, ‘Luna’ pubescent wheatgrass, ‘Bozoiskey’ Russian wildrye and ‘Tetracan’ Russian wildrye were each planted at 0.5 inch, 1.0 inch, 1.5 inch and 2 inch depths. Seedling counts were taken each Monday and Thursday for one month. At the end of one month, 25 seedlings from each treatment were clipped at soil level, dried and weighed to evaluate seedling vigor. All entries had the highest stand counts at 0.5 in planting depth except for Kentucky 31 which had a slight increase in emergence at 1 inch. Final stand counts revealed a decrease in emergence as planting depth increased. Kentucky 31 tall fescue was the least affected by planting depth and Bozoisky Russian Wildrye the most affected by the 2.0 inch depth. The percent emergence of Kentucky 31 decreased by 9% by planting at the 2 inch depth. Barton Western Wheat grass decreased by 11% at 1.5 inch and 27% at 2.0 inch depth. Luna Pubescent Wheatgrass decreased by 17% at 1.0 inch and decreased 21% at the 2.0 inch depth. Emergence for Tetracan Russian Wildrye (a tetraploid) decreased 15% at 1.5 inch and 42% at 1.5 inch and a jtotal of 70% decrease in emergence at 2.0 inch. A previous study comparing diploid and tetraploid Russian wildrye reported similar results in seedling emergence as to our study. The detraploid demonstrated a higher degree of tolerance to planting depth than the diploid. For the producer, it is important to know the recommended planting depth for each grass species and not to plant deeper than the suggested depth.

SCISSORS CLIP RESULTS

This year again, the Wisconsin Forage Council and the UW Extension Service through the efforts of local forage councils and UW Extension staff are monitoring rate of change of forage quality change. This is being done either by clipping and having forage analyzed, or by using a forage quality stick and reporting results on the scissors clip web site. There are several changes to the web site this year. The state has been divided into regions of similar growing conditions and a summary table will be visible averaging all scissors clip readings within a region by date. These will give the best summary of forage quality and rate of forage quality change within the region. An individual can also locate the results from a particular county or site within a county.

As in previous years, it is important to remember that forage quality will decline about 15 percent during the best of harvesting conditions due to respiration and leaf loss. Therefore, it is important to cut the alfalfa at a RFV about 15% percent higher than one wants to put in silo or bale.

This program has greatly help producers determine when to harvest forage to have the forage quality they want to be feeding their animals.

The location of the web site for viewing results is: cf.uwex.edu/ces/ag/scissorsclip

Winter’s Effects on Pasture Grasses

Winterkill

The previous three winters have been great for overwintering of perennial plants. This winter was a little different. There has been some loss of pasture grasses, particularly perennial ryegrass not only in Wisconsin, but throughout the northern states. Late falls and early springs with little in the way of clod temperatures do not challenge plants like an “old fashion” winter might. This past winter was more typical and indeed some ryegrass stands were thinned if not out-right killed.

There has been tremendous interest in ryegrass in recent years due in part to its importance in New Zealand, and in part to availability of newer varieties. These newer varieties claim increased winter hardiness over older varieties which had little cold temperature tolerance. Many individuals are planting perennial ryegrass/ white clover stands in which ryegrass is the only grass. These two species do work well together as they both tolerate close, frequent grazing and provide very high quality forage. The potential danger is winterkill. If the ryegrass is killed, it would leave behind a pure white clover stand which would have low productivity and high bloat potential.

We have never recommended growing ryegrass as the primary grass in a pasture mix unless it is an Italian type, which will only be grown for a single season. Otherwise, plant perennial ryegrass as a part of a mixture with other grasses and legumes to provide rapid early growth and increased forage quality.

Snow Mold

Another winter related problem being reported around the state is snow mold on grasses. While normally thought of as a disease of lawn grasses, it is showing up in isolated areas of pastures around the state. Snow mold is a highly visible disease in which leaves are dead, bleached and matted. Bleached areas can range from several inches to several feet across. In most cases, leaves of infected plants are killed but crowns and roots usually survive. As conditions dry out, snow mold will gradually disappear, but infested areas may remain as weak or even dead plants. Snow mold incidence is promoted by leaving excessive vegetation in fall, excessive thatch, excessive shade, poor drainage and drifting or piles of deposited snow. In pastures, snow mold is likely to be along fence rows or other areas where drifts accumulate. Re-growth of infected areas can be encouraged by fertilization and by removing the crust through raking or mowing.

Congratulations Congratulations to our

Forage Spokesperson Winners:

1^st Place - Bruce Boettcher

2^nd Place - Stuart Sorenson

3^rd Place - Steve Kling

Bruce Boettcher with

WFC President Tom Braun

Tri-State Hay Show

Plan to attend the 2001 Tri-State Hay Show at the Arlington Research Station on June 27. In 1998, over 3000 people attended and we are expecting an even larger turnout in 2001.