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ARS Home » Midwest Area » Columbia, Missouri » Cropping Systems and Water Quality Research » Research » Publications at this Location » Publication #160232
Title: BIOLOGICAL ACTIVITY OF SOIL UNDER ROUNDUP READY SOYBEAN PRODUCTION

Author
item MEANS, NATHAN - U OF MO
item KREMER, ROBERT
item RAMSIER, CLIFFORD - AG SPECTRUM CO

Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 2/6/2004
Publication Date: 2/9/2004
Citation: Means, N.R., Kremer, R.J., Ramsier, C. 2004. Biological activity of soil under roundup ready soybean production [abstract] [CD-ROM]. Weed Science Society of America Meeting Abstracts.

Interpretive Summary:

Technical Abstract: In 2002, 75% of soybeans (Glycine max) produced in the United States were genetically modified for glyphosate resistance or Roundup Ready (RR) varieties. Glyphosate is systemic and translocates and accumulates in plant roots and can be released into the rhizosphere. Glyphosate may affect soil microorganisms directly or indirectly by accumulating in the rhizosphere. Use of biostimulants and supplemental nutrient solutions is a possible remediation approach for alleviating potential adverse effects of glyphosate on soil microorganisms. Our research objective was to determine effects of glyphosate on microbial activity in the rhizosphere of RR soybean applied with glyphosate alone and in combination with foliar amendments. A field experiment arranged in randomized complete block with a split-block arrangement for Roundup application was conducted in 2002 and 2003 using RR soybean (DeKalb DKB38-52) grown in a Mexico silt loam (fine, montmorillonitic, mesic Mollic Endoaqualf) under light tillage. Roundup Ultra Max was applied in a strip block design to soybean (V4 - V5) at 0.84 kg ae ha-1 and main plots not receiving Roundup were sprayed with a conventional herbicide mix. At 10-days post-herbicide application, biostimulants PT-21 (9.2 kg ha-1)(21.0% N) and Grozyme (33.5 mL ha-1) were applied. Soil and plant samples taken 0, 5, 10, 15, 20 and 25 days after herbicide application were assayed for enzyme activity, respiration and total culturable fungi. Surface sterilized roots were cultured for Fusarium spp. on Komada agar. Glyphosate effects on Fusarium root colonization and soil populations varied across years and within the growing season. Soil respiration and enzyme activity were adequate indicators of effects of RR soybean on plant-microbe interactions in the rhizosphere.