نوع مقاله : مقاله پژوهشی

نویسندگان

• مریم عاشوری ¹
• بیژن یعقوبی ¹
• مددعلی رستمی ²

¹ بخش گیاهپزشکی، موسسه تحقیقات برنج کشور، سازمان تحقیقات، آموزش و ترویج کشاورزی، رشت، ایران

² گروه ساماندهی و بهبود نظام‌های بهره‌برداری از ماشین، مرکز توسعه صنایع و مکانیزاسیون، وزارت جهاد کشاورزی، تهران، ایران

چکیده

کلیدواژه‌ها

• علف‌کش سای‌هالوفوپ‌بو‌تیل + پنوکسولام
• کاربرد برگی
• حجم محلول سمپاشی
• وسایل نقلیه هوایی بدون سرنشین

عنوان مقاله [English]

Drone-based weed control in transplanted rice under different irrigation systems

نویسندگان [English]

• Maryam Ashouri ¹
• Bijan Yaghoubi ¹
• Madadali Rostami ²

کلیدواژه‌ها [English]

• Cyhalofop-butyl + penoxsulam herbicide
• Foliar application
• Spray carrier volume
• Unmanned aerial vehicles

Extended Abstract

Introduction

The adoption of spraying drones as an advanced, intelligent technology offers a strategic response to labor shortages and economic challenges in rice production. In addition to improving operational efficiency, these systems enhance input use efficiency and reduce environmental impacts, thereby supporting sustainable agricultural practices. Nevertheless, despite their growing adoption among Iranian farmers, empirical evidence on the effectiveness of drones in weed management relative to conventional backpack sprayers remains limited. While backpack sprayers in transplanted rice systems typically apply herbicides at carrier volumes of 150–350 L ha⁻¹, aerial drone applications are often conducted at much lower volumes—approximately 10 L ha⁻¹—without sufficient scientific validation. To address this gap, the present study aimed to (1) assess the impact of carrier volume on the efficiency of drone-based herbicide applications for weed control in rice, and (2) determine the optimal spray volume under flooded and non-flooded irrigation regimes in northern Iran.

Method

The experiment was conducted during the 2024 growing season at the Rice Research Institute of Iran (Rasht) using a split-plot arrangement in a randomized complete block design with four replications. The post-emergence herbicide cyhalofop-butyl + penoxsulam (OD 6%) was applied as the treatment. Main plots were assigned to two irrigation regimes—continuous flooding and intermittent irrigation—while subplots comprised five drone spray carrier volumes (10, 20, 40, 80, and 160 L ha⁻¹). Additional treatments included a conventional backpack sprayer at 350 L ha⁻¹, hand weeding, and an untreated control. The main plots (90 × 18 m) and subplots (45 × 9 m) were designed according to the UAV spraying width, with buffer zones equal in size to the subplots established between them. Smaller untreated control plots (3 × 3 m) were randomly placed within these buffer zones and protected with plastic covers to prevent herbicide drift, which were removed two hours after spraying. Spraying was performed using a hexacopter drone (Model S10) and a battery-powered Matabi backpack sprayer. Treatment effects were evaluated based on visual assessments of weed control and destructive sampling for weed biomass, weed density, rice grain yield, and yield components. Data were analyzed using the GLM procedure in SAS 9.4, with ANOVA appropriate for the split-plot design to assess the effects of irrigation method, spray carrier volume, and their interaction. Due to significant interactions for most variables, nonlinear regression models were fitted in SigmaPlot 15 to identify best-fitting functions describing weed response and rice performance under different treatments. Weed density and biomass, as well as rice biomass, biological yield, and grain yield, were all fitted using four-parameter logistic models.

Results

The results showed that the density of barnyardgrass (Echinochloa crus-galli) and bulrush (Bolboschoenus planiculmis), as well as rice yield, were significantly affected by irrigation method, carrier volume, and their interaction. Increasing carrier volume reduced weed density and biomass while increasing rice yield; however, the effect of carrier volume was more pronounced under continuous flooding than under intermittent irrigation. Under intermittent irrigation, the average carrier volume required to achieve 50% and 90% biomass reduction was nearly twice as high for barnyardgrass, while for bulrush, it was about twice as high for 50% reduction and approximately four times higher for 90% reduction than under continuous flooding. Therefore, bulrush exhibited greater tolerance to the herbicide compared to barnyardgrass, requiring, on average, approximately 36% more carrier volume to achieve 50% biomass reduction under intermittent irrigation and about 55% more under continuous flooding. Rice biomass, biological yield, and economic yield under continuous flooding reached the median biological response level at a lower carrier volume than under intermittent irrigation. Logistic model analysis indicated that the maximum statistically significant economic yield occurred at carrier volumes of 80 L ha⁻¹ under intermittent irrigation and 20 L ha⁻¹ under continuous flooding, representing an approximate 11.3% yield reduction in intermittent irrigation compared with continuous flooding. No statistically significant differences were observed in the evaluated parameters between carrier volumes of 20, 40, 80, and 160 L ha⁻¹ under continuous flooding, and between 80 and 160 L ha⁻¹ under intermittent irrigation, when compared with the conventional backpack sprayer. However, relative to hand weeding, these treatments showed a 26% and 9% lower efficacy for barnyardgrass biomass suppression under intermittent and continuous flooding, respectively, and a 30% lower efficacy for bulrush biomass suppression under intermittent irrigation. Across treatments, the maximum economic yield at the optimal carrier volumes under continuous flooding and intermittent irrigation was 4331 and 3914 kg ha⁻¹, respectively, indicating an approximate 10% reduction in yield under intermittent irrigation.

Conclusions

In post-emergence herbicide applications, this study demonstrated that applying cyhalofop-butyl + penoxsulam under flooded conditions resulted in significantly more effective weed control than under drained conditions. This enhanced efficacy is attributed to the physicochemical properties of the oil-based OD formulation, which improve herbicide stability, ensure uniform spread, and facilitate penetration in water-saturated environments, thereby increasing absorption through aerial plant tissues. In addition, physiological stresses induced by flooding—such as hypoxia, toxic gas accumulation, and restricted root growth—further weaken weed vigor and enhance their susceptibility to herbicidal action. Collectively, these factors contributed to superior weed suppression, reduced required spray carrier volumes, and improved biological and economic performance of rice under the specific agro-climatic conditions of northern Iran.

Given that increased spray carrier volumes do not compromise herbicide efficacy or crop yield, the adoption of higher application carrier volumes is advisable, particularly for high-biomass improved rice cultivars. Moreover, when formulation compatibility and technical justification are ensured, the concurrent or sequential application of herbicides with fungicides or insecticides using drones is recommended under appropriate conditions.

The drone sprayer demonstrated performance comparable to conventional backpack sprayers, with no significant differences in weed control efficacy or rice yield between methods. Additionally, due to higher application speed, lower water consumption for spray preparation, and reduced manual labor reliance, drones are a reliable alternative to traditional spraying.

Although this study confirms the efficacy of drone spraying for weed control in transplanted rice, further investigation of its technical and environmental aspects remains essential. Future research should prioritize integrating pre- and post-emergence herbicides to reduce spray carrier volumes, evaluating herbicide formulations under field conditions, determining optimal application volumes across Iran’s diverse climatic regions, assessing the physical properties of sprays and the role of adjuvants, and comparing the environmental impacts of aerial spraying with those of conventional methods to promote sustainable agriculture.