Effect of Soybean Row Width and Population on Weeds, Crop Yield, and Economic Return

• Published in: Weed technology 2007-07, Vol.21 (3), p.744-752
• Main Authors: Harder, Dana B, Sprague, Christy L, Renner, Karen A
• Format: Article
• Language: English
• Subjects: Biomass; Canopy development; crop yield; crop-weed competition; dry matter accumulation; Glycine max; glyphosate; Gross margins; herbicide resistance; herbicide-resistant crops; Herbicides; leaf area index; plant density; Planting; Population growth; profitability; row spacing; Seeding; seedling emergence; Soybeans; Vegetation canopies; vegetation cover; weed competition; Weed control; weed emergence; Weeds
• ISSN: 0890-037X; 1550-2740
• DOI: 10.1614/WT-06-122.1

Field studies were conducted in 2004 and 2005 to determine the effect of soybean row width and population on weeds, canopy closure, crop yield, and economic return in glyphosate-resistant soybean. Soybean leaf area index (LAI) was greater in 19- and 38-cm, compared with 76-cm rows from 8 to 12 wk after planting in the low, moderate, and high soybean populations. Canopy closure was delayed by 2 wk in the moderate population in 76-cm rows compared with the high population in 19-cm rows. Fewer weeds emerged in 19-cm, compared with 76-cm rows following glyphosate application, and increasing the soybean population within a row width did not influence late-season weed emergence. Weed biomass in the weedy control was greater in the very low soybean population compared with the high soybean population within each row width; however, weed biomass in the weedy control was similar in the high and moderate soybean populations. Soybean yield in the weed-free and 10-cm glyphosate treatment did not differ, and yield was greater in 19-cm rows planted at moderate or high, compared with low populations. There was no difference in weed-free soybean yield at low, moderate, and high populations within 38- and 76-cm rows. Gross margins were usually greater in 19- and 38-cm, compared with 76-cm rows. The gross margin for soybean planted in 19-cm rows was usually greater at moderate or high soybean populations compared with lower populations. In 76-cm rows, the gross margin was greatest at the low and moderate soybean populations. When rainfall or other factors limited soybean yield, increasing the soybean population from approximately 300,000 plants/ha to 445,000 plants/ha in 19-, 38-, and 76-cm rows did not result in quicker canopy closure, reduced weed emergence, or greater soybean yield and gross margins. Nomenclature: Glyphosate potassium salt, glyphosate-resistant soybean, Glycine max (L.) Merr., ‘AG2701’