Evaluation of Pre-Emergence Herbicide Application Methods on Weed Control Efficiency in Transplanted Rice in Bangladesh

Farmers mostly broadcast pre-emergence (PRE) herbicide either by mixing with fertilizer or sand or apply with irrigation water in Bangladesh. We hypothesized that broadcasting PRE herbicide by mixing with urea fertilizer or sand or applying it with irrigation water may decrease the efficacy of herbicide as compared to spraying using clean water and therefore may result in an increase in weed control costs. Farmers’ participatory on-farm trials were conducted in Bangladesh to evaluate the performance of PRE herbicide application methods on weed control efficiency and grain yield in transplanted boro (dry-season rice) and aman (wet-season rice). Six farmers’ fields were selected, and at each field, four pre-emergence herbicide application methods were evaluated, viz, broadcast by mixing with urea, broadcast by mixing with sand, spray by mixing with clean water, and application with irrigation water. At ۲۵-۳۰ DAT (before hand-weeding), the lowest weed density (۳۷-۸۱ weeds m-۲, respectively, boro and aman) was found in plots with PRE herbicide application using the spraying method. As compared to the spraying method, weed density was ۴۶, ۱۳۰ and ۳۱۶% higher in boro and ۱۶, ۱۷, and ۴۱% higher in aman, respectively, in the plots where PRE herbicide was applied using broadcast by mixing with urea, broadcast by mixing with sand and application with irrigation water. The plots having herbicide application with irrigation water required the highest labors (۳۱and ۱۷ persons-day ha-۱ in boro and aman, respectively) in manual weed control and man-day ha-۱ in manual weeding reduced by ۲۹, ۲۴ and ۶۳% in boro and ۱۳, ۶, ۴۲% in aman, respectively, in the plots having herbicide broadcast by mixing with urea, broadcast by mixing with sand and spay by mixing with clean water, in comparison to plots received PRE application with irrigation water. Rice grain yield was not affected by herbicide application methods in aman, however, in boro, grain yields were similar (۶.۳ – ۶.۵ t ha-۱) in the plots having herbicide broadcast by mixing with urea, broadcast by mixing with sand and spray by mixing with clean water but significantly lower (۵.۸ t ha-۱) in the plot having an application with irrigation water.

کلیدواژه ها:

Manual weeding ، weeding cost ، Herbicides ، weeds management ، Spraying