Effect of Row Spacing and Seeding Rate on Soybean Yield - CiteSeerX

Effect of Row Spacing and Seeding Rate on Soybean Yield Jason L. De Bruin* and Palle Pedersen

ABSTRACT

Soybean

Soybean [Glycine max (L.) Merr.] yield response to narrow row spacing has been consistently positive in the upper Midwest and new split-row planters have made narrow row soybean production feasible, yet adoption has been slow in Iowa. Wide (76-cm) and narrow (38-cm) row spacing and four seeding rates (185,000; 309,000; 432 000; and 556,000 seeds ha–1) were evaluated at three locations during 2004, 2005, and 2006 to determine seed yield in wide and narrow row spacing and four seeding rates and evaluate economic advantages associated with changes in row spacing. Soybean planted in 38-cm row spacing yielded 248 kg ha–1 greater than soybean planted in 76-cm rows after adjustment for differences in final plant populations. Maximum yield at all locations was attained at a final harvest population of 462,200 plants ha–1 but >95% of the maximum yield was achieved with final populations as low as 258 600 plants ha–1. Increased production costs associated with greater seeding rates removed the yield benefit from greater harvest plant populations. Farm size of 144 ha with at least 50% of the land base dedicated to soybean production would benefit from conversion from wide to narrow rows. To break even on the investment in a split-row planter a yield increase of 124 kg ha–1 was necessary for farms with 30% of 288 ha dedicated to soybean production. These data indicate that yield and economic benefits are sufficient to support the production of soybean in narrow rows and at seeding rates below current seeding rate recommendations.

S

oybean production in the 1960s and 1970s was conducted using row spacings ≥ 76 cm (Taylor, 1980; Weber et al., 1966). Since 1990, the trend has been toward production in rows planted at spacings 95% of the maximum yield was attained at harvest populations between 118,800 and 213,800 plants ha–1 depending on location and row spacing. (Table 4). Seeding rates of 185,000 and 309,000 seeds ha–1 were sufficient to achieve this final population for either row spacing (Table 4). These seeding rates are 30 and 17% less than the current seeding rates used by producers in Iowa in 38- and 76-cm row spacing, respectively. Large changes in harvest population were required to cause significant yield reductions indicating that the majority of populations tested reached phase III yields when increasing harvest populations do not significantly increase yield (Duncan, 1986). This type of response is similar to previous observations by Carpenter and Board (1997), Egli (1988), and Weber et al. (1966) that soybean does have the ability to compensate for space in the canopy and maintain yield.

Previous work has shown that seeds m–2 is a more important determinate of yield than seed mass (Board et al., 1999; De Bruin and Pedersen, 2008; Egli and Zhen-wen, 1991). Increased seed mass without a concurrent increase in yield, as documented in this study, indicates the seed mass increase was compensated for by fewer seeds m–2 at higher seeding rates and would be consistent with the yield response to harvest plant population reported in this study. Plant Height Plant height was 17 and 9 cm greater at both Whiting and De Witt, respectively, compared with Nevada (Table 3). Row spacing had no influence on plant height (Table 2) but final populations of 316,000 and 402,700 plants ha⫺1 increased plant height 2 and 6 cm, respectively, compared with final populations of 166,900 and 258,6000 plants ha–1. Elmore (1991) documented increased plant height was associated with plant population, but only as final stands were >346,000 plants ha–1. Lodging was not a significant problem with greater seeding rates and was not influenced by changes in row spacing (data not shown).

Grower Return Locations differed in the gross profit that remained to pay land rent, chemicals, depreciation on equipment other than the planter, and labor (Table 6). As expected, grower return followed closely with yield and both De Witt and Whiting had greater economic returns compared with Nevada. Production Seed Mass in 38-cm row spacing did not (P < 0.05) produce greater return An interaction was identified between location and row for 144 ha farms with 111,000 seeds ha–1. Our study does benefit more from the change to narrow rows due to economics differ from other reports (Egli, 1988; Elmore, 1998; Ethredge of scale. et al., 1989) that seed mass decreased as seeding rates increased. Farms that are 288 ha or greater, with a land base >30% Table 6. Soybean production grower return differences among three farm sizes, with three corn–soybean rotations, based on yield differences among three locations and 38- and 76-cm dedicated to soybean producrow spacing, in Iowa from 2004 to 2006. Grower return differences account for yield change, tion, would benefit financially by ownership and repair costs, and hauling and handling charges associated with conversion from changing to a narrow row system 76- to 38-cm row spacing as well as seed cost differences for each seeding rate. as long as a yield increase of 124 144 ha 575 ha 1294 ha kg ha–1 can be attainted. Yield Main effects 70/30 60/40 50/50 70/30 60/40 50/50 70/30 60/40 50/50 increases of 17 to 248 kg ha–1 $ ha –1 yield were necessary, depending Location on farm size and percentage of De Witt 922a† 929a 933a 942a 943a 944a 945a 946a 947a land in soybean production, to Nevada 645b 651b 655b 664b 666b 667b 668b 669b 669b Whiting 1012a 1018a 1022a 1031a 1033a 1034a 1035a 1035a 1036a achieve an economic benefit for Row spacing the conversion to reduced row 38 cm 861a 875a 883a 901a 904a 906a 908a 909a 911a spacing (Table 7). The risk associ76 cm 858a 857a 858b 857b 857b 857b 857b 857b 857b ated with purchasing a narrow † Values followed by the same letter are not significantly different at P ≤ 0.05. row planter decreases dramatically 708

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Table 7. Soybean yield increase required to cover the economic cost for the conversion from conventional 76-cm row spacing production to 38-cm row spacing production with a split-row-planter for nine farm sizes and three corn–soybean rotations.

as farm size increases, although small farms could expect a return on this investment because the overall yield benefit from this study and other reports support that narrow row spacing will increase yield by an amount >248 kg ha–1 (Table 7). Only the costs of new equipment were determined and the purchase of used equipment would reduce one or more of the following requirements: farm size, soybean production acres, and yield gain necessary to achieve economic benefit from narrow row soybean production.

Ratio of corn/soybean production Farm size ha 144 288 431 575 719 863 1006 1150 1294

CONCLUSION The majority of farmers in large soybean producing states such as Illinois and Indiana use row spacing 144 ha with levels of soybean production >30% of the land base would benefit economically from narrow row soybean production. Changes in seeding rates contributed to significant yield changes but not to changes in profitability. Adoption of narrow row spacing and seeding rates less than current production recommendations could be used to reduce production costs and increase yield and profitability. ACKNOWLEDGMENTS The authors thank Jodee Stuart and Adriana Murillo-Williams for their technical assistance and Joseph Lauer for his help conducting the analysis of covariance with plant population. This research was funded by the Iowa Soybean Association. REFERENCES Ablett, G.R., W.D. Beversdorf, and V.A. Dirks. 1991. Row spacing and seeding rate performance of indeterminate, semideterminate, and determinate soybean. J. Prod. Agric. 4:391–395. Akoi, T., K. O’Donnell, and M.M. Scandiani. 2005. Sudden death syndrome of soybean in South America is caused by four species of Fusarium: Fusarium brasiliense sp. nov., F. cuneirostrum sp. nov., F. tucumaniae, and F. virguliforme. Mycoscience 46:162–183. Alessi, J., and J.F. Power. 1982. Eff ects of plant and row spacing on dryland soybean yield and water-use efficiency. Agron. J. 74:851–854. American Society of Agricultural and Biological Engineers. 2007. Published standards database. Available at www.asabe.org/standards/searchpur.html [accessed 30 Aug, 2007; verified 7 Feb. 2008]. Andrade, F.H., P. Calvino, A. Cirilo, and P. Barbieri. 2002. Yield responses to narrow rows depend on increased radiation interception. Agron. J. 94:975–980. Board, J.E., M.S. Kang, and B.G. Harville. 1999. Path analyses of the yield formation process for late-planted soybean. Agron. J. 91:128–135. Bullock, D., S. Khan, and A. Rayburn. 1998. Soybean yield response to narrow rows is largely due to enhanced early growth. Crop Sci. 38:1011–1016. Buzzell, R.I., T.W. Welacky, and T.R. Anderson. 1993. Soybean cultivar reaction and row spacing eff ect on Sclerotinia stem rot. Can. J. Plant Sci. 73:1169–1175. Carpenter, A.C., and J.E. Board. 1997. Branch yield components controlling soybean yield stability across plant populations. Crop Sci. 37:885–891. Cooper, R.L. 1977. Response of soybean cultivars to narrow rows and planting rates under weed-free conditions. Agron. J. 69:89–92.

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70/30 248 124 83 62 50 41 35 31 28

60/40 kg ha –1 186 93 62 47 37 31 27 23 21

50/50 149 74 50 37 30 25 21 19 17

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2008