Context Mechanical weed control method with autonomous weeding machine provides an alternative way for farmers to reduce the use of herbicides. This method can not only reduce the chemical load in the environment, but also have many other benefits, such as loosening soil and promoting plant growth. However, little is known in this regard. Therefore, field experiments were conducted to determine the benefits of mechanical weeding on rice growth.
Objective The main objective of this study was to investigate the effects of mechanical weeding on weed control, rice growth characteristics and yield. The ultimate goal was to provide an efficient, non-chemical weed control method for rice production.
Methods Three field experiments were conducted in 2020 and 2021 using an autonomous weeding machine that combined inter-row and intra-row weeding technologies. Three different rice cultivars (Qingyang, Yuetaiyouzhan, and Huahang 57) were grown in the three experimental sites in South China. At each site, the experimental treatments were mechanical weed control and chemical weed control. Plants with no weed control were taken as the control of the experiment. Weed control efficacy and crop performance were measured.
Results The results showed that mechanical weeding using the autonomous weeding machine was able to achieve a high level of weed control efficacy (on average 80 %) for three weeks after weeding, and also reduced farmers' time and labor for weed management. Mechanical weeding significantly increased the tiller numbers by 7–23 %, SPAD values by 3–7 %, as well as the total biomass by 45 % after the jointing growth stage, compared with the chemical weed control method. Furthermore, the mechanical weeding obviously increased the activities of superoxide dismutase and peroxidase in the uppermost leaves of rice plants and grain yield by 2–11 % at the harvest maturity stage.
Conclusion Mechanical weeding using the collectively inter-row and intra-row weeding technology was capable of avoiding using herbicides with no losses in weed control efficacy and grain yield. Due to the mechanical stimulation and inter-tillage effect of the autonomous driving weeding machine, the mechanical weed control method promoted rice growth, which provided an efficient and non-chemical weeding method for rice production.
Significance The continuing advancement of this emerging technology is of great significance to the development of weed control in field crops. The results could be used to enhance rice production using mechanical weed control methods and develop smart-agriculture practices in China and similar agroecological regions around the globe.
The weed problem in paddy fields is one of the main factors reducing the crop yield in rice production because they use part of the resources that are essential for rice growth. Weed management in paddy fields has significant seasonality, short weeding period, and large amount of labor, which brings more challenges (Zhu et al., 2020). Consequently, weed control is perceived to be an important aspect of research in paddy field management. Weed control methods include chemical, mechanical, biological, thermal, electric, and cultural approaches (Zeng et al., 2021). Due to the advantages of economy and labor savings, chemical weed control is a frequently used and efficient method, but it has high risk of herbicides contamination. The evolution of herbicide-resistance weeds will decrease the efficacy of chemical weed control, and it may cause adverse effects on crop growth and yield as well. With the accumulation of layers in the food chain, there could be herbicide residues in human bodies. Therefore, many countries require to reduce their dependence on herbicides, especially the European Union, which promotes the adoption of mechanical weed control strategies (Melander et al., 2015).
Mechanical weeding has always been an environment-friendly, sustainable weeding substitute in agricultural history, and it is also the most important alternative to chemical weed control (Van Der Weide et al., 2008; Kunz et al., 2015). As a rapid weed control technology to replace herbicides, mechanical weeding has reduced production costs and labor force, and enhanced weeding efficiency in recent years. With the rapid development of organic agriculture, this weeding method is progressively more favored by organic rice producers. Research and development of mechanical weed control methods for rice has been the focus of many studies in the past two decades (Van Der Weide et al., 2008; Melander et al., 2015), mainly driven by regional policies and the transition to organic production. The primary emphasis has been on the management of inter-row weeds which grow between crop rows and can be easily managed by most inter-row cultivators (Melander et al., 2015). However, the challenge for mechanical weeding is to control the weeds in the intra-row area of crops. Current intra-row mechanical weeding practices such as weed harrowing, torsion weeding (Melander et al., 2015), and finger weeding have been studied for weed control (Ascard et al., 2008). These methods are not guided by any intelligent system and are non-selective, relying on weed-crop root differences when passing through intra-row areas. Since intra-row weeding machines tend to injure seedlings when operating near seedlings, farmers need precise alignment operations to minimize the damage to seedlings.
Collectively inter-row and intra-row weeding technology was able to achieve a high level of weed control efficacy (on average 80 %) for three weeks after weeding, and also reduced farmers’ time and labor for weed management. Compared with chemical weed control method, although mechanical weed control method reduced the plant height but increased the number of tillers by 7–22 %, SPAD values by 2–8 %, and total biomass by 45 % after the jointing growth stage, which promoted the rice growth. The superoxide dismutase and peroxidase activities of the leaves were significantly higher under the mechanical weeding due to the mechanical stimulation and inter-tillage effect of the weeding machine. Based on these benefits, the mechanically weeded rice had the highest theoretical and harvest yields, with yield increases of 2–11 % compared to chemical weed control, because of its higher number of productive panicles and percentage of grain filling. Our study showed that the inter-row and intra-row mechanical weeding method using the autonomous driving machine could increase rice yields while reducing labor use and chemical loads. Continuing advancement in this emerging technology will have a great potential for environment-friendly agriculture in the development of weed control in field crops. For future research, experiments should investigate the effect of autonomous weeding machine on soil physicochemical properties and microorganisms in paddy fields, so as to further understand the additional benefits of adopting mechanical weed control on the field crop growing environment.