Abstract
Different weeding frequencies (WFs)―0WF, 2WF, 4WF, 6WF, and 8WF―were adopted in an organic rice field to investigate their influence on weed types, rice and weed biomass, rice tiller and weed number, N concentration, and N uptake. The study field was located in Tsuruoka, Yamagata, Japan. Rice (cv. Sasanishiki) was planted from May to September 2019, and all weeding events were carried out until 49 days after transplantation (DAT) using a rotary weeder. Rice and weed samples were collected at 60, 88, and 110 DAT. Echinochloa crus-galli (E. crus-galli), Schoenoplectus juncoides, and Monochoria vaginalis (Burm. f.) were the most commonly found weeds. High weed diversity was observed at both 6WF and 8WF, E. crus-galli was the dominant weed at 0WF. Compared to 0WF, 2WF displayed a significantly decreased weed biomass. However, at 8WF, the weed biomass was reduced by 79.0%, the rice biomass was increased by 277%, and the rice tiller number was almost three times higher than that at 0WF and 110 DAT. Compared to 0WF, a significantly increased rice N uptake was observed at 4WF, and rice N uptakes achieved at 6WF and 8WF were two and four times higher than those at 0WF, respectively. Higher weeding frequencies provide notable benefits in suppressing weeds and supporting rice growth, especially in N uptake competition with weeds.
Highlights
Organic agriculture is a comprehensive system that produces healthy food and contributes to the maintenance of a sustainable and healthy environment [1,2]
There was no significant difference in the rice tiller numbers at 60 days after transplantation (DAT) (Figure 1)
A significant difference was found at 110 DAT when 8WF with the highest tiller number was the only treatment significantly different to 0WF
Summary
Organic agriculture is a comprehensive system that produces healthy food and contributes to the maintenance of a sustainable and healthy environment [1,2]. Weed competition is the main factor affecting rice, especially in organic farming systems in which herbicides have been prohibited to more precisely control weed growth [4]. Controlling weeds in organic agriculture is crucial, and ineffective weed control can result in a decrease in crop yield [5]. Weed existence as a limiting factor in rice fields represents a serious issue hindering the achievement of an optimum rice yield [9,10]. Neglecting weed growth without controlling nutrient enrichment results in a lower rice yield [11]. It is possible for organic fields to produce 10 t ha−1 of weed biomass, which would result in no rice yield [9]. Weeding is crucial in order to eliminate the negative effect of weed disturbance on crop yield in terms of both quality and quantity [12]
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