Critical period of weed control in transplanted tomato (Solanum lycopersicum) in Kermanshah

To determine the critical period of weed control in transplanted tomato in Kermanshah, in order to reduce the weed control costs.

a field experiment was conducted in a randomized complete block design with three replications. Treatments were divided in to two series. The first one consisted of six weed interference until 0, 15, 30, 45, 60 and 75 days after transplanting and then weeds were removed until the end of the growth period, and the second one consisted of six weed control until 0, 15, 30, 45, 60 and 75 days after transplanting and then permit to weeds to complete to crop until the end of growth season.

The results showed that full weed interference reduced total dry matter, maximum leaf area index and fresh fruit yield of tomato by 67.2, 36.5 and 83.5 percentages, respectively. The critical period for weed control was determined using logistic and gompertz functions. Critical period of weed control based on 5 and 10 percent acceptable yield loss was determined from 14 to 89 and from 19 to 78 days after transplanting, respectively, that was equal to from 103 to 1189 and from 144 to 1003 growth degree days after transplanting, respectively.

Generally due to the low planting density and the non-complete canopy closure, it is necessary to weed control be started from two to three weeks after tomato transplanting and continued for five to six weeks.