Title: Introduction. Glyphosate Interactions with Physiology, Nutrition, and Diseases of Plants: Threat to Sustainability Authors
Submitted to: European Journal of Agronomy
Publication Type: Popular Publication
Publication Acceptance Date: July 7, 2009
Publication Date: September 21, 2009
Citation: Yamada, T., Kremer, R.J., Castro, P.R., Wood, B.W. 2009. Introduction. Glyphosate Interactions with Physiology, Nutrition, and Diseases of Plants: Threat to Sustainability. European Journal of Agronomy. 31(3):111-113. Technical Abstract: One of the most significant inputs necessary for successful conventional crop production is synthetic chemical herbicides to control a wide variety of weed infestations. Glyphosate, the active ingredient in the herbicide, “Roundup”, became very popular after introduction in the 1970’s for non-selective weed control in fallowed fields and non-cropped areas of orchards, vineyards, and timber plantations. The development of no-tillage (no-till) for row-cropping systems largely depended on glyphosate to control growing vegetation in fields prior to planting. This “burndown” application eliminated the need for tillage and allowed planting directly into soil beneath a mulch of dead plant residue. The introduction of transgenic, glyphosate-resistant (GR; “Roundup Ready”) crops in the mid-1990’s provided cost-effective weed management allowing control of a broad spectrum of weeds on an “as needed” basis and reducing the need for numerous pre- and post-emergence herbicides. The current widespread cultivation of GR crops has made glyphosate the most extensively used herbicide worldwide. However, use of glyphosate is not without potential adverse side effects. Certain of these potential problems are linked to complex interactions between glyphosate usage strategies and the timely bioavailability of plant nutrient elements; the transfer of glyphosate and/or its primary metabolites to, and subsequent effects on, susceptible non-target crops; indirect effects on rhizosphere microorganisms and host-plant resistance to pathogens; and selection for glyphosate-resistant weeds. These problems collectively raise serious concerns regarding the sustainability of cropping systems in which glyphosate is the primary weed management tool. Based on these concerns, an international Symposium, “Mineral Nutrition and Disease Problems in Modern Agriculture: Threats to Sustainability?”, was convened in Piracicaba-SP, Brazil, on 20-21 September 2007, to present and discuss up-to-date research on problems of plant nutrition and disease linked to glyphosate use, present and critique sustainable alternative management strategies, and propose future research efforts. Key themes included interactions of glyphosate with nutrient availability to crop plants; interactions of glyphosate with plant pathogens and disease development in crop plants; and impacts of glyphosate on plant nutrition and microbial interactions in GR cropping systems. The Symposium provided a forum to bring together the current understanding of the numerous physiological, nutritional, soil chemical, phytopathological, and biological factors that interact with glyphosate management whether situated in conventional (plantation, orchard, row crops) or in transgenic agroecosystems. This understanding is essential for developing alternative approaches within management systems to overcome the constraints to crop productivity and health. Some of the recommendations that emerged from the Symposium included reducing the use of glyphosate in perennial culture by using mulching systems to suppress weeds. Development of efficient methods for using cover crops in annual crops for weed suppression and possible increased availability of soil micronutrients was discussed. Several approaches for improving productivity in GR cropping systems included selection of cultivars with high Mn-uptake efficiency, delayed application of micronutrients (Mn, Zn, Fe, and Cu) after glyphosate treatment, and use of cultural practices to minimize glyphosate impact. It is hoped that the articles in this Special Issue will serve as valuable information sources for those interested in a better understanding of the interactions of glyphosate with crop plants and that this information facilitates development of improved sustainable agricultural production systems.