Efficacy of weed extract as a bioherbicide in rice (Oryza sativa L.) cultivation

Weeds around rice crops can cause competition and then must be controlled. Pre-emergence weed control by utilizing weed extract as herbicides is the alternative solution for substituting synthetic herbicides. In addition, allelopathic compounds of weed can inhibit the seed germination of other species. This study aims to know the efficacy of weed extract types as bioherbicides to inhibit weed growth and increase rice yields. The study was conducted from 2021–2022 in the greenhouse, Ngestiharjo, Yogyakarta, Indonesia. The Padjajaran Agritan variety was used. This study was a pot experiment arranged in a complete randomized design (CRD) with three replications. The weed extract treatment consisted of four types: goat weed, nut grass, siam weed, and cogon grass, which was applied in two ways: seven days before and when planting seedlings. In addition, one control was added, namely without weed extract application. In this study, 81 polybags were used. Each replication consisted of three plant samples. The results showed that the application of weed extract could inhibit weed growth, including the individual weed number and weed dry weight. In addition, it can also increase tiller number, shoot dry weight, panicle number, and grain dry weight of rice. The nut grass and cogon grass were given panicle number and grain dry weight higher than goat weed and siam weed. The right time for weed extract application was seven days before planting for nut grass and when planting for cogon grass to increase the rice yield. Nut grass and cogon grass extracts have efficacy higher than nut grass and siam weed in inhibiting weed growth and increasing rice yield. Therefore, we suggest that nut grass and cogon grass extract can be used for pre-emergence weed control in rice cultivation.