Rick Mascagni and Robert Bell

Research has found a consistent sorghum yield response to row widths narrower than 40 inches, particularly on alluvial soils. On Macon Ridge soils, narrow rows tend to yield better than wider rows in years with adequate rainfall, while wider rows are superior to narrow row widths in rain-deficient years. For rows less than 30 inches, crops are generally planted on flat seedbeds, which preclude the use of furrow-irrigation. Raised beds are necessary for furrow irrigation and important for drainage, particularly on heavy clay soils. Multiple rows planted on 40-inch-wide raised beds maintain cultural advantages of raised beds and permit furrow irrigation. Cultural practices such as hybrid selection and seeding rate may interact with row spacing. The objective of this research was to evaluate the influence of row configuration (multiple rows per bed) and seeding rate on yield performance of three grain sorghum hybrids, differing in maturity.

Field experiments were conducted in 2002 and 2003 on Gigger silt loam at the Macon Ridge Research Station at Winnsboro to evaluate the influence of row configuration and seeding rate on yield performance of three hybrids, differing in maturity. Row configurations included single, twin and triple rows on 40-inch-wide raised beds. Single rows were centered on 40-inch-wide beds. Twin rows were approximately 20 inches apart and triple rows were approximately 10 inches apart centered on 40-inch-wide beds.

Hybrids evaluated were the very-early maturing Asgrow Reward, early-maturing Dekalb DK36E, and medium/late-maturing Dekalb DK52. Grain sorghum was planted on April 29, 2002, and April 23, 2003, at seeding rates equivalent to 6, 8, and 10 seeds per foot on single row; 3, 4, and 5 seeds per foot on twin rows; and 2, 2.7, and 3.4 seeds per foot on triple rows. All recommended cultural practices of the LSU AgCenter were followed, including the use of seed treated with the insecticide Gaucho.

Sorghum yields were affected by row configuration in one of two years of this study. In 2003, yields were increased an average of 14 percent by both twin and triple rows. Yields were similar between twin and triple rows. Yield response to multiple rows was primarily due to increased head size. Head size, number of kernels/head, was increased approximately 24 percent by both twin and triple rows. Hybrids responded similarly to multiple rows, regardless of maturity. Optimal seeding rate was the equivalent of 8 to 10 seeds per foot for single row, 4 to 5 seeds per foot for twin row, and about 3 seeds per foot for triple row.

This study indicates that planting multiple rows on raised beds may be beneficial in some years. Wide rows may have more of an advantage in dry years, while narrower rows generally produce higher yields with adequate soil moisture. When rainfall is adequate or irrigation available, cultural practices such as narrow row spacing may be required for maximum yield. As row spacing narrows, distance between plants increases allowing for better utilization of soil moisture and light. This strategy of planting multiple rows on raised beds provides the benefits of narrow rows as well as the ability to furrow irrigate. More information is needed to fully evaluate the advantages of planting multiple rows on raised beds, particularly under irrigated conditions.

Acknowledgment: Louisiana Soybean and Grain Research and Promotion Board

Rick Mascagni, professor, and Robert Bell, research associate, Northeast Research Station, St. Joseph, La.

(This article was published in the winter 2005 issue of Louisiana Agriculture.)