2000 Research Results

Evaluation of soybean germplasm under Pennsylvania Conditions

The variety and germplasm testing program was conducted at two locations: Landisville in Lancaster County, and Rock Springs in Centre County. The Landisville site is used to evaluate material in Groups III and IV in full season and double crop plantings. Maturity Groups II and early III are evaluated at Rock Springs. Yield, maturity, height, lodging, seed quality and seed size data was obtained for each location. Herbicide tolerant varieties (glyphosate RR and sulfonylurea STS) were tested in separate trials at both locations for full season and at Landisville for double crop plantings.

The growing conditions during the 2000 season were characterized by below normal temperatures. Only June, in Lancaster County, had temperatures above normal. The rest of the growing season in Lancaster and all of the months in Centre County had below normal temperatures. Despite the cool growing season, soybean was mature enough in all trials before a killing frost occurred. Rainfall was below normal in both May and July in Centre County and in July and August at the Lancaster site.

In 2000, 66 private and seven public varieties were evaluated in the full season test (which included 31 normal germplasm, 35 RR and 7 STS varieties) at the Landisville site. Sixty-one private and seven public varieties were evaluated in the full season test (which included 31 normal germplasm, 31 RR and 6 STS varieties) at the Rock Springs site. The double crop test at Landisville included 43 private and eight public varieties (which included 23 normal germplasm, 22 RR, and 6 STS varieties). Thirteen breeding lines, from the Mid-Atlantic testing program, were evaluated at the Landisville site. We continue to cooperate with researchers at USDA in evaluating forage breeding lines. In 2000, 46 advanced breeding lines were evaluated for yield and quality at the Rock Spring site.

The average yields for each test are as follows:

Landisville

Full season normal germplasm 70.0 bu/ac

Full season RR 69.7 bu/ac

Full season STS 79.2 bu/ac

Double crop normal germplasm 50.6 bu/ac

Double crop RR 50.8 bu/ac

Double crop STS 47.2 bu/ac

Rock Springs

Full season normal germplasm 59.4 bu/ac

Full season RR 68.0 bu/ac

Full season STS 57.3 bu/ac

— Elwood Hatley, Pennsylvania State University, $6,000

SCLEROTINIA STEM ROT (WHITE MOLD) OF SOYBEANS: FIELD TESTING OF AGRONOMIC CONTROL MEASURES AND INVESTIGATIONS OF SOYBEAN RESISTANCE TO WHITE MOLD.

Sclerotinia white mold is a chronic problem in Pennsylvania. Resistant soybean cultivars are the first line of defense, but relatively few cultivars adapted for Pennsylvania have high levels of resistance to this disease. Crop rotation is another control measure, but this pathogen attacks almost 400 species of plants. Corn and small grains are good candidates for rotation and several years out of soybeans Should reduce the severity of white mold in the next soybean crop. The field experiments funded by the Pennsylvania Soybean Promotion Board and the Northeast Soybean Promotion Board were designed to test whether the impact of white mold can be reduced by modifying agronomic practices.

In 2000, in cooperation with a producer in Muncy, we tested the effect of row width, planting density and the herbicide COBRA on the incidence of white mold. Row widths were 14", 21" and 28". Plant densities were: high (150,000 plants/acre) and low (75,000 plants/acre). COBRA treatments were: COBRA applied at growth stage R1 at a rate of 8 oz/acre, and no COBRA. The herbicide COBRA has shown promise as a tool to manage white mold. It does not affect the pathogen, but rather stimulates the plant to produce defense compounds.

The incidence of white mold was less than 15 percent but we did detect a significant row width x plant density x COBRA interaction. COBRA completely suppressed development of white mold. In the treatments without the herbicide, white mold was significantly reduced in the 28" row widths when plant density was low. Plant density affected the location of the white mold lesions on the soybean plants. Plant grown under low plant density had significantly more nonmain stem lesions whereas plants in the highdensity treatments had more mainstem lesions. Mainstem lesions are often lethal and frequently affect yield. The low incidence of white mold in 2000 makes definitive conclusions about row width and planting density impossible. COBRA suppresses white mold. However, because of the potential for a slight yield reduction due to herbicide burn in the absence of white mold, this approach can only be recommended where there is a chronic, serious white mold problem. Unfortunately, the decision to use COBRA to manage white mold must be made at the R1 growth stage, prior to the appearance of the disease.

In 1999 we tested whether plant size was related to white mold resistance. Healthy plants were collected from alI treatmenis in early August. The dry weight of the leaves per plant was determined. There was a highly significant (P=0.0001) relationship between leaf dry weight and white mold incidence. The greater the leaf dry weight, the lower the incidence of white mold. Plants with greater numbers of leaves may have a higher photosynthetic capacity and thus a greater ability to fix carbon and produce the compounds needed to express resistance to white mold. In 2000, we repeated the study but found no relationship between leaf weight of healthy plants and incidence of white mold. There was a significant affect of leaf weight on the location of the white mold lesions. More lesions were on main stems when leaf, weights were low, which supports our theory that plants with more leaves may be better able to defend against white mold.

— Barbara Pennypackers, Pennsylvania State University, $32,934

Effect of Herbicide Programs on Weed Shifts in CornSoybean Rotation

A cornsoybeancorn rotation and a soybeancornsoybean sequence have been conducted using six different herbicide treatments. The primary weed species in the study since 1998 are common lambsquarters (Chenopodium album), common ragweed (Ambrosia artemisiifolia), Pennsylvania smartweed (Polygonum pensYlvanicum), yellow foxtail, (Setaria lutescens), and yellow nutsedge (Cyperus esculentus). These five species continue to be dominant in both corn and soybean although yellow foxtail is in decline and yellow nutsedge was less prevalent in 2000, particularly in soybean.

In 2000, the following results and trends were observed in relation to the different herbicide programs. Common lambsquarters, common ragweed, Pennsylvania smartweed, yellow foxtail and yellow nutsedge were effectively controlled in both corn and soybean. In general, the ALS post treatment tended to be less effective than the glyphosate based treatments, especially in soybean; the Pinnacle mixture did not effectively control all lambsquarters ragweed or yellow foxtail. In addition, common ragweed escapes were noted with a single application of Roundup in corn, where the ragweed emerged following herbicide application. The two pass soil programs that included soil residual treatments were consistently effective on all weeds, with the exception of volunteer corn (Zea mays) in soybean.

All herbicide programs controlled Pennsylvania smartweed, regardless of crop rotation or year. Apparently, this species is fairly susceptible to the programs used in this experiment. Yellow foxtail was effectively controlled with all herbicide programs and appears to be on the decline in all treatments including the untreated check. Unlike 1999, control of yellow nutsedge was relatively good with all herbicides in 2000. Nutsedge was a less competitive weed than in the previous year perhaps because of increased rainfall and better crop competition.

Several species that were noted in 1999 were again present in 2000. In particular, wild buckwheat (Polygonum convolvulus) and volunteer corn were present in some treatments. Wild buckwheat is beginning to become problematic in the untreated check, the Roundup alone treatments and the ALSbased program, particularly in corn. Wild buckwheat and Pennsylvania Smartweed belong to the same genus (Polygonuni), yet Pennsylvania smartweed does not appear to be as tolerant to glyphosate or ALS type herbicides. This weed could become a serious problem in these types of herbicide programs. Volunteer glyphosateresistant corn is a problem in all except the Post ALSbased program in soybean where Assure is an effective treatment. Although black medic was noted as a increasingly common species in 1999, it was not a problem in 2000. In addition to the species already mentioned, a number of other species were noted in 2000 again in low frequency and included corn chamomile (Anthemis arvensis), small flower galinsoga (Galinsoga parviflora), witch grass (Panic capillare), prostrate spurge (Euphorbia maculala), fall panicum (Panicum dichotomiflorum), common yellow woodsorrel (Oxalis stricta), velvetleaf (Abutilon theophrasti), prostrate knotweed (Polygoinan aviculare) and eastern black nightshade (Solanum ptycanthum). These species probably represent the seedbank that could shift directions in the future.

Corn and soybean grain yields did not differ in 1999 or 2000 due to herbicide treatment. Only the untreated check was significantly less than the other treatments. Weed competition was severe in the untreated check, reducing yield by at least 50 percent compared to where a herbicide was used. Soybean yields were higher 1999 compared with 2000, while 2000 produced slightly better corn yields compared to the previous year.

— William Curran, Pennsylvania State University, $8,374

ENHANCED SOYPROTEIN INTERACTIONS

Introduction. The protein remaining after oil is extracted from soybeans is a relatively lowvalue commodity most commonly used as animal feed. Soy can be used as human food, but market is small and specialized (e.g., tofu, soymilk). It is the longterm goal of this research to develop a valuable and versatile food ingredient from soy protein and thus increase the value of the soy crop. To convince ingredient manufacturers they should look again at soy we must first be able to show them something different and far beyond their experiences with the crop.

Previous studies funded by the PA Soybean promotion board in my laboratory have revealed a mechanism to understand soy protein functionality and more recently we have used small amounts of charged surl'actant to modify the functional properties. The purpose of the Year 2000 phase of the work was to investigate how these ingredients interact with other important food ingredients (i.e., sodium and calcium chloride).

Methods. Soy protein (SPI, 10 percent) solutions were prepared with different amounts of added sodium dodecyl sulfate (SDS, 05 percent). The pl I was adjusted (37) with small amounts of concentrated acid or base and sodium (02 M) or calcium (00.2 M) chloride. The solutions were allowed to equilibrate overnight prior to viscosity and solubility determination.

Results. A representative functionality plot is shown as the inset Figure. In this Figure the concentration of calcium chloride and SDS are shown as the X and Yaxes respectively and the lines shown link solutions of equal viscosity. This figure shows that high concentrations of SDS can usefully increase the viscosity of SPI but not in the presence of calcium. Similar functionality maps (not presented) were developed for the other input and response variables. The viscosity of the SDSmodified soy ingredient was less affected by high concentrations of sodium chloride and increased with pH and concentration of surfactant. Solubility tests are under way at time ofwriting.

We conclude from these measurements that the performance of the modified ingredient is different to conventional SPI and its behavior is affected by the presence of other ingredients.

— John Coupland, Pennsylvania State University, $13,631

Bruce, we could scan the figure as art if you think it would mean anything to the reader

CAN A COVER CROP IMPROVE CONTINUOUS SOYBEAN?

Five grasses (rye, ryegrass, S.oats, W. wheat, timothy) were broadcast seeded into standing soybean the end of September 1999 in Lancaster and Centre Counties. In December at the Lancaster location, grass plants per square foot varied from 11.7 (wheat) to 39.0 (ryegrass). Three grasses (W. wheat, rye, ryegrass) produced biomass DM per acre in excess of 1.5 tons prior to killing the grasses for 2000 soybean planting. Soybean were seeded the end of May in Centre County and the first week of June in Lancaster. The soybean were seeded at both locations no-till with a unit planter in 15" rows.

There were no significant soybean yield differences at either location in 2000. At the Lancaster site, soybean yields varied from 50.4 to 42.8 Bu/A. At the Centre County site, soybean yields varied from 38.0 to 35.3 Bu/A. At the Lancaster site, this is the third year of continuous soybean. The highest average yield (1999,2000) since the grasses were established was from the rye treatment (52.6 Bu/A), and the lowest average yield was the no cover treatment (42.2 Bu/A).

— John Yocum, Pennsylvania State University, $2,158

HERBICIDE RESISTANT SOYBEAN: THEIR YIELDING ABILITY?

Three soybean cultivars were selected from previous Pennsylvania soybean variety trials. The cultivars selected were Wilken 3468, representing a nonherbicide tolerant variety; Wilken 3464RR, representing a glyphosate tolerant variety (RR); Pioneer Brand 93B81, representing a sulfonylurea tolerant variety (STS).

The soybean were seeded June I at the Lancaster site and May 31 at the Centre County site. At the Lancaster site, the soybean were seeded in 15" rows, and at the Centre site, the row width was 7". For weed control at both locations, Roundup Ultra was used on the glyphosate tolerant variety (RR) and Synchrony + Assure II on the sulfonylurea tolerant variety (STS). On the nonherbicide tolerant variety, Dual + Gemini was used at the Lancaster site and Basagran + Fusilade at the Centre site for weed control.

There was no significant soybean yield difference between the cultivars at the Lancaster location. At the Centre location, there was no significant yield difference between the nonherbicide tolerant cultivar and the glyphosate tolerant cultivar, but the STS cultivar did produce significantly less yield than the yield produced by the non herbicide tolerant and glyphosate tolerant cultivars. While not significant, the highest yield at both locations was produced by the nonherbicide tolerant variety (average of both locations=62.8 Bu/A). The glyphosate tolerant variety averaged over both locations produced a yield of 58.8 Bu/A, and the STS variety 53.4 Bu/A.

— John Yocum, Pennsylvania State University, $2,158