Twin-Row Vs. Single-Row Soybean Production In the Mid South As Influenced by Planting Date and Seeding Rate.

Comparisons of single-row vs. twin-row soybean (Glycine max (L.) Merr.) production on a Beulah fine sandy loam (coarse-loamy, mixed thermic Typic Dystrochrepts) and Sharkey clay (Vertic Haplaquept) were made in 2009 and 2010 at Stoneville, MS..  Seeding rates of 20, 30, 40, and 50 seed m^-2 were planted on beds in 25cm twin-rows with 102cm centers or 102cm single-rows.  Planting dates were made in , mid-April, mid-May, representing the ESPS and a mid-June common to double-crop soybean after wheat (Triticum aestivum L.) .  Data included established plants at R4, nodes and pods plant^-1, yield, seed weight, and seeds m^-2.  Twin-rows yielded more than single-rows on both soils (3.8 Mg ha^-1 vs. 3.6 Mg ha^-1 on the sandy loam; 4.2 Mg ha^-1 vs. 4.0 Mg ha^-1 on the clay).  Yields in 2010 were less due to drought and heat stress. Delayed planting decreased yields.  Increasing seeding rates had no effect. Twin-rows on both soils had more plants m^-2 than single-rows.  Differences in nodes plant^-1 were noted but did not affect yield. Pods plant^-1 did not differ between row configurations on either soil.  Seeding rates above 30 seeds m^-2 are not economically beneficial.  Seed weights differed slightly. Twin-rows generally produced more seeds per m² than single rows.  Delayed planting will result in decreased yields. The small yield increases combined with equipment costs makes it important to consider a twin-row planter’s usefulness in other crops before investing in it for soybean production.