Soil chemical properties as influenced by long-term glyphosate-resistant corn and soybean production in the central Great Plains, USA

Glyphosate-resistant (GR) corn (Zea mays L) and soybean (Glycine max (L) Merr.) production and glyphosate application could affect soil chemistry due to indirect effects on soil organic matter (SOM) and nutrient cycling. We determined soil chemical properties after 15-yr of glyphosate application, continuous GR corn (CC) and GR corn soybean rotation (CS) under no-tillage. Herbicide treatments were 1) glyphosate at 0.42 and 2) 0.84 kg a.e. ha(-1) each applied twice in all years, 3) an alternating treatment of glyphosate at 0.84 kg ha(-1) applied twice followed the next year by a non-glyphosate herbicide treatment, and 4) a non-glyphosate herbicide treatment in all years. Results showed that crop rotation and soil sampling depth affected SOM, pH, and nutrient concentrations. Soil pH, exchangeable Ca and K concentrations at the soil surface were reduced with CC production. In contrast, SOM, Fe, Mn, NO3-N, SO4-S and soil P concentrations in the top 7.5 cm of the soil increased with CC production. Glyphosate application affected concentrations of P, NO3-N, SO4-S and Fe but not pH, Ca, Mg, Mn or Zn. Findings of this long-term study showed that crop management practices including herbicide program and crop rotation could affect soil chemical properties but cropping systems with CC increased soil surface fertility compared to CS production. (C) 2016 Elsevier B.V. All rights reserved.