Introduction: Uniform distribution of rice seeds in seedling trays is a critical factor that significantly influences the growth performance and overall yield of rice crops. Proper seed placement ensures optimal seedling density, reduces competition among plants, and promotes uniform germination and development. However, many farmers, especially in regions where resources are limited, rely on manual or traditional methods for seed sowing due to the high cost and limited availability of automatic seed-sowing machines. These manual methods are often time-consuming, labor-intensive, and prone to uneven seed distribution, which can negatively impact seedling quality. Therefore, there is a pressing need for an affordable, simple, and efficient device that can facilitate quick and precise sowing of rice seeds in seedling trays. This study aims to design, manufacture, and evaluate a handheld mechanical seed-sowing device tailored to meet these requirements.
Materials and Methods: The seed-sowing device was designed using SolidWorks, a three-dimensional CAD software, to ensure precision and functionality in the design phase. The device features two main containers: one for holding rice seeds and another for soil. It incorporates soil and seed distributors, carrying handles for ease of use, and a transmission system comprising gears, a chain, and a chain wheel.

• Body: Constructed from stainless steel alloys 304 and ST37 steel to provide durability, corrosion resistance, and lightweight characteristics.

• Transmission Gears: Manufactured from PTFE (Teflon) to reduce friction and wear, ensuring smooth operation.

• Seed metering: Designed as a grooved roller made from aluminum alloy, chosen for its strength and lightweight properties.

• Soil Distributor: Made from a rigid plastic conveyor, enabling consistent soil delivery.

The device was tested using rice paddy seeds with varying quantities ranging from 70 grams to 180 grams per seedling tray to simulate different sowing densities. The device allows adjustment of soil thickness both below and above the seeds, ranging from 0.5 to 2 centimeters, controlled by an adjustable cover of the seed metering device. This feature aims to optimize seed coverage and protection. Performance evaluation focused on the accuracy of seed quantity placement and consistency of soil coverage. Data were collected and analyzed to determine the correlation between the device’s settings and the actual sowing outcomes.
Results and Discussion: The evaluation demonstrated that the designed device effectively achieves uniform seed distribution within seedling trays, ensuring consistent spacing and reducing seed wastage. Detailed testing revealed that the relationship between the number of seeds dispensed and the recommended sowing quantity showed a high degree of accuracy, with a coefficient of determination (R²) of 0.99, indicating excellent precision in seed placement. This level of accuracy underscores the device’s reliability in achieving targeted plant populations, which is crucial for maximizing crop yield and health. The adjustability of soil thickness proved to be a valuable and user-friendly feature, enabling users to customize seed coverage according to specific agronomic recommendations for different rice varieties and environmental conditions. The device consistently maintained soil thickness within the predefined range, with a maximum observed error of 12% in cases of over-sowing and 15% in under-sowing coverage. These deviations fall well within acceptable limits for practical agricultural applications, reflecting the device’s robustness in real-world conditions. Furthermore, the mechanical design, which included the use of low-friction PTFE gears and a lightweight yet sturdy aluminum seed distributor, significantly contributed to smooth operation, accuracy, and durability under repeated use. The handheld nature of the device enhanced its usability and portability, making it particularly accessible to smallholder farmers, who often lack access to expensive and complex machinery. This user-centered design approach is expected to facilitate widespread adoption in rural farming communities, ultimately improving sowing efficiency and crop establishment. Overall, the device addresses key challenges associated with manual seed sowing by improving speed, accuracy, and uniformity, which are essential for optimizing seedling growth and subsequent crop yield.
Conclusion: This study successfully designed, manufactured, and evaluated a cost-effective, simple, and handheld mechanical seed-sowing device tailored for rice seedling trays. The device demonstrated high precision in seed distribution and adjustable soil coverage, meeting the agronomic requirements for optimal seedling growth. Its affordability and ease of use make it a practical alternative to expensive imported automatic seed-sowing machines, potentially benefiting small-scale farmers by enhancing sowing efficiency and crop establishment. Additionally, the device's lightweight design and ergonomic handle reduce operator fatigue, allowing for prolonged use during busy planting seasons. Its modular components also simplify maintenance and repairs, increasing overall durability and lifespan. The seed-sowing device also supports sustainable agricultural practices by minimizing seed wastage and ensuring uniform germination, thereby contributing to improved resource management. Future work may focus on field trials to assess long-term impacts on seedling vigor and yield, as well as exploring adaptations for other crop types, such as vegetables and legumes, to broaden its applicability across diverse agricultural systems.