Weeds and Conservation Agriculture

Abstract

In crop production agriculture, tillage is used mainly for weed control. The advent of effective herbicides eliminated the need for wide crop rows to accommodate horse or tractor drawn cultivation equipment since herbicides can replace in-crop tillage and allow narrower row widths that maximize crop growth and yield. Until recently, the primary disadvantage of total no-till crop production was an increase in perennial weeds that required primary and seedbed tillage for control. Most herbicides used pre-emergent in crops only controlled germinating weed seeds and not established perennial plants. Most postemergent herbicides lacked selectivity for effective perennial weed control. Post harvest or before planting herbicide treatments for perennial weeds were limited because of possible soil residual or improper weed size for efficacy. The development of glyphosate tolerant crops and the use of pre and post-harvest glyphosate have essentially eliminated the perennial weed disadvantage for no-till agriculture. Glyphosate also controls annual weeds with excellent selectivity in tolerant crops. Glyphosate contributed to an estimated 60% no-till soybean production in Ohio and various herbicides allowed about 20% not-till corn production in Indiana, Illinois and Iowa in 2000. Herbicide usage increases with less tillage; but herbicides require far less energy in manufacture and use than tillage, an important benefit with increasing energy costs. This and other benefits of no-till crop production, such as reduced soil erosion and greater stored carbon, now can be achieved simply, effectively, and economically through herbicides that are safe to the user and the environment.