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Soybean Planting Date & Maturity Effects on Yield & Oleic Acid Profiles

 

Soybean Planting Date and Maturity Effects on Yield and Oleic Acid Profiles in the Mid-Atlantic Region

By Robert Kratochvil, Ph.D.1, Kirk Reese2 and Bill McCollum3

 

Summary

  • Research was conducted to evaluate performance of two Pioneer® brand Plenish®^ high oleic soybean varieties and four conventional varieties planted over a range of dates.
  • Late May plantings had highest yield, followed by early and late June plantings. Mid-July plantings had the lowest yield in this three year trial.
  • There were no significant differences in oleic acid expressed as a percent of total oil among planting dates and tested varieties.
  • Oleic acid levels were maintained between 70% and 80% for both Plenish high oleic soybean varieties across all planting dates, compared to an average of 23% for the conventional varieties.

Background

Pioneer brand Plenish high oleic soybeans offer growers an opportunity to capture value from identity preserved markets. High oleic soybean oil is recognized as a healthier alternative to current commodity soybean oil. End users in the Mid-Atlantic region have recognized the value of using oil from Plenish high oleic soybeans and continue to grow an identity preserved market.

Growers routinely plant soybeans throughout the spring and summer months in the Mid-Atlantic Region, both in full-season systems and in double-crop systems following a barley or wheat crop. Some growers have elected to utilize earlier maturing soybeans in double-crop systems, however little research is available to address what effect different planting dates and soybean maturities have on yield in this environment. Also unknown is the effect on oleic acid levels in soybean oil as planting date is extended further into the growing season.

Objectives

Research was conducted to evaluate the agronomic performance of 2 Pioneer brand Plenish high oleic soybean varieties and 4 conventional (non-Plenish) varieties planted over a range of dates that are considered normal for full-season and double-crop soybean production in Maryland. The goal of the research was to develop management recommendations that will optimize yield, oil content, and overall soybean quality.

Aerial view of soybean planting date and maturity trial at the University of Maryland.

Aerial view of soybean planting date and maturity trial at the University of Maryland Wye REC near Queenstown, MD.

Study Description

Field experiments were conducted during the 2013 through 2015 growing seasons at the Wye Research and Education Center near Queenstown, MD. The soybean plots were planted under irrigated conditions and supplied with water as needed to minimize drought stress. Drip irrigation was supplied in 2013 and 2014, and lateral overhead irrigation was used in 2015. Appropriate tillage and weed control practices were employed along with foliar fungicide and insecticide applications at later growth stages.

Six soybean varieties with a maturity range of 3.2 to 4.8 were planted at 4 dates representing full-season and double-crop systems (Table 1). All varieties were planted in 15-inch rows at 175,000 seeds/acre. Each 75-ft plot consisted of 6 rows. Four center rows of each plot were harvested for yield and adjusted to 13% moisture. Soybean samples were collected at harvest and submitted for oil and protein analyses.

Table 1. Maturity groups of Pioneer brand soybean varieties included in the study.

Maturity groups of Pioneer brand soybean varieties included in the study.

*All Pioneer products are varieties unless designated with LL, in which case some are brands.

Linolenic acid, total oil and protein content, seed size, and purple seed stain were also measured. Although differences exist, they were subtle and not reported in this Field Facts. Mean separation and least significant difference values were conducted using Student’s t-test. Means with the same letters are not significantly different at 5% level.

Results

2014 yield was different than 2013 and 2015 when averaged across planting dates and tested varieties (Figure 1). Planting date effect on yield was significant. Late May plantings had highest yield, followed by early and late June plantings. Mid-July plantings had the lowest yield in this three-year trial (Figure 2).

Year effect on soybean grain yield averaged among planting dates and tested varieties, 2013-2015.

Figure 1. Year effect on soybean grain yield averaged among planting dates and tested varieties, 2013-2015.

Planting date effect on soybean grain yield averaged among years and tested varieties, 2013-2015.

Figure 2. Planting date effect on soybean grain yield averaged among years and tested varieties, 2013-2015.

While there was an incremental increase in yield with later soybean maturity, there were no significant differences observed when averaged across years and planting dates. Therefore, mean separation was conducted on planting date by year (Figure 3). Yield of the mid-July planting or earlier maturing soybean varieties may have been impacted by Dectes stem borer (Dectes texanus) infestations later in the growing season.

Planting date effects by year on soybean yield.

Figure 3. Planting date effects by year on soybean yield.

There were no significant differences in oleic acid expressed as a percent of total oil among planting dates for the 2 Plenish high oleic soybean varieties in the study (Figure 4.) Oleic acid was maintained between 70 and 80% for both varieties over all planting dates. Average oleic acid content for non-Plenish high oleic soybean varieties was 23.3% (data not shown.)

Oleic acid content expressed as a percent of total soybean oil among planting dates and years.

Figure 4. Oleic acid content expressed as a percent of total soybean oil among planting dates and years.

Management Implications

Growing environment (location and year) had a significant influence on soybean yield potential — average yield in 2014 was significantly lower than 2013 or 2015.

Late May plantings had the highest yield in all 3 years of the trial. There was no difference between early and mid-June plantings, which indicates an opportunity to realize greater soybean yield when planted in a double-crop system. Mid July plantings had the lowest yield of all planting dates, except for similar yield with late June planting in 2013.

There was an incremental increase in yield with later maturing soybean varieties as planting was delayed; however, there was no significant difference in yield among varieties when averaged among planting dates and years (data not shown.) It is recommended to plant later maturing soybeans, maturity group IV or greater, after the end of June to avoid late summer heat and drought risks, especially in dryland environments.

Oleic acid levels trended slightly lower as planting was delayed; however 70% to 80% levels were maintained among all planting dates and years, and differences among planting dates were not significant. The earlier maturing Plenish high oleic soybean varieties tested in this trial performed well in late May and June plantings. Newer, later maturing Plenish high oleic soybean varieties are better suited for July planting dates in the mid-Atlantic Region.

Acknowledgements

Research conducted by Robert Kratochvil, J. Draper, J. Street, D. Murphy, M. Sultenfuss, L. Thorne, and M. Islam of the University of Maryland in collaboration with Bill McCollum and Kirk Reese of DuPont Pioneer as a part of the Pioneer Crop Management Research Awards (CMRA) Program. This program provides funds for agronomic and precision farming studies by university and USDA cooperators throughout North America. The awards extend for up to four years and address crop management information needs of DuPont Pioneer agronomists and customers, and Pioneer sales professionals.


1 Associate Professor, University of Maryland
2 DuPont Pioneer Agronomy Research Manager
3 DuPont Pioneer Field Agronomist


2013-2015 data are based on average of all comparisons made in 1 location through Dec. 31, 2015. Multi-year and multi-location is a better predictor of future performance. Do not use these or any other data from a limited number of trials as a significant factor in product selection. Product responses are variable and subject to a variety of environmental, disease, and pest pressures. Individual results may vary. Pioneer® brand products are provided subject to the terms and conditions of purchase which are part of the labeling and purchase documents.

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