Effect of red clover ( Trifolium pratense L.) kill with glyphosate on tillage implement draft

Abstract

Forages are often used in crop rotations in eastern Canada to both improve soil structure, add soil organic matter, and provide livestock feed. After the last cut of forage has been harvested in the forage year, the forage regrowth is usually killed with the non-selective herbicide glyphosate prior to fall tillage. Producers have noticed lower tractor power requirements for primary tillage for areas treated with glyphosate compared to non-treated areas. Field experiments were conducted over 2 years on a fine sandy loam soil near Charlottetown, PEI, Canada to measure the effect of red clover ( Trifolium pratense L.) kill by glyphosate on implement draft requirements in a subsequent tillage operation. Plots were established in a field of red clover, with three glyphosate treatments, early, late, and control (none). The glyphosate was applied with a field sprayer at the recommended rate of 0.9 kg a.i. ha −1. Draft measurements for a chisel plow at three nominal depths, 70, 140 and 210 mm, and for a moldboard plow at nominal 170 mm depth were made using an instrumented research tractor. In 2000, results showed a reduction in draft of 20, 25 and 18% for a chisel plow operating at 70, 140 and 210 mm nominal depths, respectively, and a 12% reduction in draft for a moldboard plow following the glyphosate treatment. In 1999, the treatment effect was not significant ( P>0.05) for the moldboard plow, and all but one chisel plow depth. However, there was a trend towards lower draft for both plows accompanying the glyphosate treatment. It is suggested that the reduction in tillage implement draft was due to breakdown of tissue structure and loss of mechanical strength of the plant roots accompanying translocation of glyhposate into the plant roots.