Abstract

1. Abstract A study at Stoneville, MS compared twin-row vs. single-row plantings made in mid-April of MG VI and MG V soybeans seeded at 20, 30, 40, and 50 seeds m-2 in 2008, 2009, and 2010. Data from 2010 has changed some conclusions presented in the original abstract as noted in Italics. Seed yields of the MG IV cultivar were greater than those of the MG V cultivar. Row type and seeding rate had no impact on seed yield though final plant populations increased with increased seeding rates and twin-row plantings had higher final plant populations than single-row plantings. Cultivars did not differ in pods plant-1but single row plantings produced more of this component and increased planting rates tended to decrease it.The MG V cultivar had a greater LAI (7.7) than the MG IV (6.1) and the twin-row plantings had a greater LAI (7.0) than the single-row plantings (6.7).Seed weight did differ between cultivars (15.6 mg for MG IV vs. 14.7 mg for MG V)but not among planting rates, or row type. Twin-row plantings do not appear to have a yield advantage over conventional single rows and seeding rates above 20 seeds m-2 are not advisable given current seed cost and the lack of yield increases with higher seeding rates. Results Table2. Leaf Area Index (LAI), seed yield, seed weight, and seed bulk density of an irrigated MG IV and MG V soybean cultivar grown in a 102 cm single-row or twin-row configuration at seeding rates of 20, 30, 40, and 50 seeds m-2.† Table 1. Seed yields of two irrigated soybean cultivars grown in single or twin rows at varying seeding rates.† Comparisons of MG IV and MG V Soybeans Planted in Twin and Single Rows at Varying Seeding RatesH. Arnold BrunsUSDA-ARS, MSA Crop Production Systems Research Unit Stoneville, MSarnold.bruns@ars.usda.gov For means within a column or a row lsd@ P<0.05=0.3 †Means of 3 years (2008-2010) and 4 replications lsd@P<0.01‡ 0.8 1.0 53 12.8 †Means of two planting configurations and four replications ‡lsd is to compare all means with in a column, both between cultivars and years Table 4. Nodes and pods per plant of two irrigated soybean cultivars (94M80 and GP533) grown at varying seeding rates in 102 cm beds. † Table 3. Established plants at R4 among two irrigated soybean, cultivars (94M80 and GP533) in single-row and twin-row 102 cm beds.† Materials and Methods The study was conducted at Stoneville, MS during 2008, 2009, and 2010. The soil at the site was a Beulah fine sandy loam (coarse-loamy, mixed thermicTypicDystrochrepts). The experimental design used in this study was a randomized complete block replicated four times with a split plot arrangement of treatments. Whole plots were one of two cultivars, an MG V, Armor GP-533 (Armor Seed Company, Waldenburg, AR)1 and an MG IV Pioneer brand 94M80 (Pioneer Hi-Bred Int., Huntsville, AL)1 which were assigned at random within each block. Sub-plots were assigned at random within each whole plot and consisted of a combination of either a single-row or twin-row planting configuration and a seeding rate of 20, 30, 40, or 50 seeds m-2. Single-row plantings were made using an Almaco cone plot planter (Allen Machine Company, Neveda, IA)1 and twin-row plots were planted with a four unit Monosem (Edwardsville, KS)1 twin-row planter set on 102 cm centers between planting units and 25 cm between rows within a unit. Individual plots were four ridges wide planted 11 m long and end-trim to 9 m at the V4 growth stage as defined by Pedersen (2004). Plots were furrow irrigated beginning at R1 and continuing to R6. Data collected included an estimate of leaf area index at R4 to early R5 using an AccuPAR model LP-80 ceptometer (Decagon Devices, Pullman, WA)1, plants m-2, nodes and pods plant-1 at R6, seed yield, seed moisture content at harvest, seed bulk density, and seed weight. Seed yields were adjusted to a standard of 110 g kg-1. Data were analyzed using PROC MIXED of SAS (Research Triangle, NC)1. Year at both sites was considered and analyzed as a fixed effect. †Means of 4 replications. Lsd@ P<0.05=5 for means within a column and across a row. ns lsd@P<0.05=10 †Means of two cultivars, (94M80 and GP533) two row types (single and twin) and 4 replications. Conclusions Twin-row plantings appear to have no yield advantage over single-row of MG IV and MG V soybeans grown in the ESPS in the lower Mississippi River Valley. Seeding rates > 30 seeds m-2 in either row configuration are likely not a profitable practice. Given the stability of yield across seeding rates in both row types and the increase in established plants with increased seeding rates, one must conclude that fewer seed pod-1 were produced at the higher seeding rates. The lack of differences in seed weight with increases in seeding rate (data not shown) and the lack of a trend in pods plant-1 related to seeding rate further support this conclusion. Summary The MG IV cultivar (94M80) produced more seed than the MG V (GP533) at all seeding rates in this experiment (Table 1). Increasing seeding rates had no impact on seed yield. Twin-row plantings only yielded more over single-row plantings with the MG IV cultivar at the higher two seeding rates. Leaf area index was greater for the MG V cultivar 2 of 3 years but yielded less (Table 2). Seed weight for both cultivars within a given year was the same. Only in 2009 did the MG IV cultivar have a greater seed bulk density. Twin-row plantings generally had more plants established by R4 than single-row plantings except in 2008 when there were no differences (Table 3). Relative stand establishment rates ranged from 46% to 100% of the seeding rates (data not shown). Nodes plant-1 were unaffected by row type, cultivar, or seeding rate (Table 4). No consistent trend in pods plant-1 was observed across seeding rates in the 3 years of the experiment. Reference Pedersen, P. 2004. Soybean growth and development. Iowa State Univ. PM 1945. Ames, IA Disclaimer 1Mention of trade names or commercial products is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U. S. Department of Agriculture. Questions Questions concerning this poster should be directed to the author via email : arnold.bruns@ars.usda.gov