Weed management objectives

From the standpoint of crop protection, weed management has three principal objectives (1) Weed density should be reduced to tolerable levels. Experimental studies with a range of species indicate that the relationship between crop yield loss and weed density can be described by a rectangular hyperbola (Cousens, 1985 Weaver, Smits & Tan, 1987 Norris, 1992 Blackshaw, 1993 Knezevic, Weise & Swanton, 1994 Chikoye,Weise & Swanton, 1995).The specific parameters of this relationship change...

Population dynamics of annual weeds in ridge tillage

Weed Population Dynamics

The effect of ridge tillage on weeds is distinctive from other types of tillage in that seeds do not move randomly relative to the crop row. In ridge tillage sometimes referred to as till-plant a crop is planted on ridges formed the previous growing season Figure 4.8 . During planting, the surface of the ridge is scraped into the inter-row valleys. Seeds that were shed onto the ridge the previous season are thus moved to the valleys where seedlings can be destroyed by inter-row cultivation....

Thermal and electric weeders

Thermal Weeder

Flame weeders briefly expose weeds to a propane or butane flame at 800-1000 C Ascard, 1995a , which disrupts cell membranes and leads to rapid dehydration Ellwanger, Bingham amp Chapell, 1973 Ellwanger et al., 1973 . A bank of burners can flame a wide area to kill weeds before crop planting or crop emergence, or to defoliate plants prior to harvest Tawczynski, 1990 . Shielding such machines to contain the heat increases their efficiency. Irrigation a few days before planting ensures that the...