A non‐chemical weed control strategy, introducing duckweed into the paddy field

Abstract

BACKGROUND Herbicide resistance in weeds and environmental pollution resulting from excessive application of chemical herbicides keeps increasing. Development of environment‐friendly and effective weed management strategies are required for sustainable agricultural production. In this study we investigated the effects of duckweeds (Landoltia punctata (G. Meyer) Les & D. J. Crawford and Spirodela polyrhiza (Linnaeus) Schle iden) introduction on the weed community and rice growth in paddy fields. RESULTS The study was conducted in the two rice‐growing seasons (2018 and 2019) with three treatments: rice grown without duckweed introduction (CK), with L. punctata introduction (LP), and with S. polyrhiza introduction (SP). On average, LP and SP significantly reduced total weed density by more than 90% and 97%, respectively. Early in the rice‐growing season, both duckweed species completely prevented weed growth. Further, both species significantly promoted rice plant growth in the advanced stages. SP significantly improved grain yield of rice by 23%. Light transmittance, temperature of the floodwater and soil, floodwater pH, and dissolved oxygen content significantly decreased following introduction of the duckweeds, indicating that the duckweeds introduction might inhibit weeds growth by altering environmental factors. CONCLUSION This study provides a possible environment‐friendly way to inhibit weed biomass in the paddy field by introducing duckweeds and interpreted the possible reasons of the impacts of duckweed on environmental variables. Weed control is beneficial for rice growth. Duckweed coverage might be limited in open fields and the associated practice requires additional investigation. © 2022 Society of Chemical Industry.

A Preliminary Study of the Impacts of Duckweed Coverage during Rice Growth on Grain Yield and Quality

“…This indicates that the duckweed had adverse effects on the rice at the early-growth stage but had beneficial effects at the late-growth stage, even under the circumstance of growing in the fertile pond-bottom soil, which was rich in nutrients. This result agrees with those in a previous report by Wang et al [ 26 ], where the authors found trends in rice-tillering inhibition and spikelet enhancement caused by the duckweed coverage in a paddy field. The tillering inhibition was attributed to the nutrient competition between the duckweed and rice seedlings [ 14 ] or the suppression in the tiller-bud outgrowth induced by the duckweed shading [ 26 ].…”

“…This may have the same role as the N fertilizer applied at the panicle initiation practiced by farmers to increase the spikelet number and, thereby, increase the yield. In a recent report, a rice yield increase of 10.8–23.7% by duckweed coverage in a paddy field was attributed to the increase in the panicle size or grain number per panicle [ 26 ]. In addition, duckweed coverage in a paddy field prevented weed growth, especially in the early rice season [ 26 ], because the duckweed coverage blocked the sunlight and impeded the photosynthesis of weeds.…”

“…In a recent report, a rice yield increase of 10.8–23.7% by duckweed coverage in a paddy field was attributed to the increase in the panicle size or grain number per panicle [ 26 ]. In addition, duckweed coverage in a paddy field prevented weed growth, especially in the early rice season [ 26 ], because the duckweed coverage blocked the sunlight and impeded the photosynthesis of weeds. This non-chemical weed-control strategy may provide an environmentally friendly way to improve the nutrient utilization of rice.…”

“…Although a number of studies have investigated the effects of the duckweed coverage in paddies on the rice growth and yield, no consensus has been reached because positive [ 19 , 20 ], negative [ 14 ], and no significant effects [ 27 , 28 ] of duckweed on the rice yield have been reported ( Table S1 ). The effects of the duckweed treatment on the rice yield seem to be dependent on soil types [ 29 ], duckweed species [ 26 ], and fertilizer applications [ 22 ]. Duckweed coverage significantly increased the rice yield by 13.2% and 16.9% when urea and biogas slurry were applied, respectively; however, no significant yield increase was found when slow-release fertilizer or null fertilizer was applied [ 22 ].…”

Investigation into the Synthesis, Bioactivity, and Mechanism of Action of the Novel 6-Pyrazolyl-2-picolinic Acid as a Herbicide

“…Weeds are native to many ecosystems and are characterized by the fact that they can typically survive under harsh conditions and compete with other plants for water, nutrients, and sunlight. The impact of weeds on crop yield is estimated to vary from 8% to 37% worldwide. − The use of artificially synthesized chemical herbicides is currently the most economic and effective measure for weed growth management. However, over time, the weeds evolve to exhibit resistance to such herbicides, and the application of herbicides of different chemotypes has also become problematic as some weeds have evolved cross-resistance to multiple chemotypes herbicides. , …”