18th Congress of the European Society for Agronomy

Deciphering crop-weed competition in aerobic rice culture in a temperate climate condition

Not scheduled

15m

Les Dortoirs (1st floor) (The Couvent des Jacobins)

Poster Synergies between disciplines Poster session #1

Speaker

Ms Rina Fukunaga (University of Tokyo, JAPAN)

Description

1. Introduction: Aerobic rice culture employs direct-seeding of dry rice seeds into unpuddled soils, with the field kept unflooded throughout the growing period to save irrigation water (Kato and Katsura, 2014). The method often leads to severe yield loss compared with the conventional transplanting method in flooded fields due to weed infestation (Jabran and Chauhan, 2015). For the judicious use of herbicides and the effective mechanical weeding in sustainable agriculture, we need to understand the weed community growths and their impacts on crop yield. The objective of this study was to evaluate the effects of various weed management practices on the growths of weeds and crop in aerobic rice culture in a temperate climate condition of Japan.
2. Materials and Methods: A field experiments was conducted at the Institute for Sustainable Agro-ecosystem Services, University of Tokyo, Nishitokyo, Japan (35°44'N, 139°32'E) during the summer of 2023. Rice (cv. Hitachihatamochi) was aerobically grown at a seeding rate of 100 kg ha-1. Three weed management treatments — no weeding, hand weeding at 35 days after sowing, and complete weeding — were compared (Fig. 1). Shoot growths of both rice and weeds were measured four times, as well as grain yield at maturity. Additionally, light interception of rice and weed canopies were separately measured to estimate the cumulative radiation intercepted and radiation use efficiency of rice and weeds. In no weeding plots, 16 quadrats in total were placed, and the coverage of each weed species was monitored during the crop growth period.
3. Results: The crop yield in the no weeding treatment was 25% compared with complete weeding. In no weeding, cumulative radiation intercepted was only 68% of that in complete weeding, due to severe light competition with weeds. Interestingly, there was no significant difference in radiation use efficiency of rice crop between no weeding and complete weeding. Meanwhile, the cumulative radiation intercepted of rice crop receiving only one weeding at 35 days after sowing was comparable to that in complete weeding, resulting in no yield loss (351 vs. 349 g m-2). In no weeding plots, the 16 quadrats were classified into four clusters based on the coverage of each weed species. Even with similar total weed coverage, the quadrats with higher proportions of Persicaria lapathifolia and Digitaria ciliaris exhibited significantly lower rice yields than others．
4. Discussion: This study, for the first time to our best knowledge, directly measured the light interception and radiation use efficiency of crop and weed community separately in natural crop-weed competition (Colbach et al., 2021). This study suggests that a single weeding at an early growth stage can alleviate light competition between rice and weeds, thereby maintaining higher yields in aerobic rice culture in a temperate climate condition of Japan. It was also evident that not all weed species contribute equally to crop yield reduction. Particularly, Persicaria lapathifolia showed vigorous growth immediately after rice emergence, which made the early weeding effective.
5. References: Colbach N, Colas F, Cordeau S, Maillot T, Queyrel W, Villerd J, Moreau D. The FLORSYS crop-weed canopy model, a tool to investigate and promote agroecological weed management. Field Crops Research 261, 108006. Kato Y, Katsura K. 2012. Rice adaptation to aerobic soils: physiological considerations and implications for agronomy. Plant Production Science 17, 1-12. Jabran K, Chauhan BS. 2015. Weed management in aerobic rice systems. Crop Protection 78, 151-163.