Effects of Glyphosate and Foliar Amendments on Soil Microorganisms in Roundup Ready Soybean.
(S03-means307665-oral)
Authors:
N.E. Means* - Univ. of Missouri
R.J. Kremer - USDA-ARS, Columbia, MO C. Ramsier - Ag Spectrum Co., DeWitt, IA
Abstract:
In 2002 75% of soybeans (Glycine max) produced in the U. S. were glyphosate resistant or Roundup Ready® (RR) varieties. Glyphosate translocates and accumulates in plant roots and meristems.
Glyphosate exuded in the rhizosphere may affect soil microorganisms. Biostimulants may remediate potential adverse effects of glyphosate. Objectives were to determine effects of glyphosate on microbial activity in RR soybean rhizosphere and assess if foliar amendments might offset those effects. Field studies (randomized complete block split for herbicide application) were conducted in 2002-2003 with DeKalb DKB38-52 RR soybean on Mexico silt loam (Mollic Endoaqualf). Roundup Ultra Max® was applied (V4-V5 stage) at label rate; main plots without Roundup® received conventional herbicides. At 10-d 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 periodically post-herbicide application were assayed for enzyme activity, respiration and total culturable fungi. Surface-sterilized roots were cultured for Fusarium spp. Glyphosate stimulated Fusarium root colonization of RR soybean. Foliar
amendments seemed to suppress Fusarium root colonization by 20 d post Roundup application.
Changes in soil microbial activity may affect nutrient transformations, nutrient uptake and plant-microbe interactions.
Speaker Information: Nathan Means, Univ. of Missouri, 302 ABNR BldgUniv. of Missouri, Columbia, MO 65211; Phone: 573-882-6408; E-mail: [email protected]
Session Information: Monday, November 3, 2003, 8:25 AM-11:00 AM Presentation Start: 9:15 AM
Keywords: transgenic soybean; rhizosphere microorganisms; soil Fusarium; soil microbial ecology
