Optimizing Manual and Chemical Weeding Combinations and Herbicide Dosage for Strategic Upland Rice Weed Management

Weeds pose a significant threat to upland rice production, causing yield losses of up to 45% and threatening food security. Two field experiments were conducted over three cropping seasons to develop sustainable, adapted weed management strategies. Study 1 compared various combinations of mechanical and chemical weed control methods in three weeding frequencies at a three-week time interval. The highest paddy yield of 3.5t/ha was achieved in treatments where the first and second weeding were done mechanically, and the third weeding was performed using herbicide. This yield was significantly higher than that obtained with chemical weeding alone, underscoring the importance of integrated weed management. Chemical weed control at first weeding significantly affected rice tillering. Study 2 investigated quantity reduction, but with the same quality of herbicide application. The treatments were- recommended, half, and quarter herbicide dosages. For half and quarter dosages, herbicide quantity, application speed, and time were halved and quartered, respectively, but herbicide concentration and plot areas remained constant. Reducing the herbicide quantity reduced the yield by 17.6% and 25% for half and quarter, respectively. These yields were not significantly different from the recommended application rate. From this result, if rightful precautions such as sprayer calibration and application speed are taken depending on size and nature of the weeds, smaller quantities of herbicide can be used to effectively control weeds in upland rice. This approach is more economical, time-saving, and minimizes the negative environmental impacts associated with excessive herbicide usage.