Two-Row Push Seed Drill with 3D-Printed Swappable Metering Plates for Groundnut and Ragi, with Field Spacing Trials

Small farmers in the Pune, Satara and Kolhapur districts still sow groundnut by dropping seeds behind a bullock plough and ragi (nachni) by broadcasting or hand dibbling. Both methods waste seed and give uneven plant spacing; hired labour for dibbling is increasingly hard to find at sowing time. Tractor-drawn planters exist, but they are uneconomical on plots of one or two acres on sloping land.

This project designs and fabricates a push-type, two-row manual seed drill whose seed-metering unit uses interchangeable 3D-printed plates. A farmer swaps a PLA or PETG plate (each with a different cell size and count) to switch between groundnut, ragi, and later soybean or maize, without buying a new machine. The ground wheel drives the metering plates through a chain and sprocket, so seed spacing stays constant regardless of walking speed. Furrow openers and a light chain covering device complete the unit.

Unlike demo-only models, the drill is tested in two stages: a laboratory sticky-belt test to measure spacing at different speeds, and field trials on a farmer's plot in Junnar taluka, where missing index, multiple index, quality-of-feed index, seed damage, field capacity and operator effort are measured and compared with traditional sowing. The project fits SPPU 2019 course Project Stage I (402047) for design and Stage II (402053) for fabrication, testing and the final report.

Abstract

A two-row, push-type seed drill with ground-wheel-driven, interchangeable 3D-printed metering plates was designed, fabricated and tested for groundnut and finger millet. Laboratory tests on a sticky belt and field trials measured spacing uniformity using missing, multiple and quality-of-feed indices, along with seed damage, field capacity and push force. The drill aims to give uniform plant spacing at low cost for small, sloping plots where tractor planters are impractical.

Introduction

Precision in sowing directly affects plant population and yield. Recommended spacing for kharif groundnut in Maharashtra is commonly 30 cm between rows and 10 cm between plants; for line-sown ragi, about 22.5–30 cm between rows with close in-row spacing. Hand dropping cannot hold these values consistently. Manual seed drills developed by agricultural universities and ICAR institutes use fixed metering plates, typically machined or cast, so a farmer needs a different machine or an expensive spare for each crop.

Literature gap

Published manual-drill studies mostly report a single crop and laboratory spacing only. Very few use additive manufacturing for metering parts, and fewer report standard field indices on actual farm soil. Interchangeable printed plates reduce the cost of multi-crop use and can be reprinted locally when worn.

Proposed work

• Design the frame, wheel, drive ratio and metering housing for two crops.
• Design and print plates with cell geometry based on seed dimensions measured from local seed lots.
• Fabricate the drill in the college workshop.
• Test in the lab and in the field; compare with traditional sowing on seed use, spacing and time.

Feasibility

• Technical: the department has an FDM printer, CAD lab and welding bay; CURA is used in the additive-manufacturing course.
• Economic: estimated build cost ₹7,000–9,000 including chain, sprockets, bearings and filament.
• Field access: a farmer has agreed to provide a 0.1 ha strip at sowing time; timing must match the monsoon sowing window or a pre-kharif irrigated plot.

Small farmers sowing groundnut and ragi on one- to two-acre plots face three problems at sowing: uneven plant spacing from hand dropping, high seed use because of over-dropping, and shortage of labour during the short sowing window after the first good rain. Existing manual drills use fixed metering plates for one crop, and tractor planters are uneconomical and unsuitable for small sloping fields. The problem addressed is to design, fabricate and field-test a low-cost, push-type seed drill whose metering plates can be swapped between crops, and to quantify its spacing accuracy, seed saving, field capacity and operator effort against traditional sowing.

The drill is a two-row, push-type implement for groundnut and ragi on tilled soil in small plots. Fertiliser metering, powered drive and sensors are excluded. Field trials are limited to one plot and one season; yield comparison requires a full crop cycle and is listed as future work. Plates are tested for one season of wear only.

Design approach

Design-build-test methodology across the two SPPU project stages, with an experimental evaluation phase.

Stage I (402047, Semester 7)

1. Literature and field survey: farmer interviews in Junnar taluka on current sowing practice, plot size, seed cost and labour charges.
2. Seed properties: length, width, thickness (vernier, 100 seeds each), thousand-seed mass, bulk density and angle of repose.
3. Concept selection among inclined plate, vertical rotor and fluted roller using a weighted decision matrix (cost, multi-crop ability, accuracy, ease of manufacture).
4. Design calculations:
   • Drive ratio: in-row spacing S = π·D·(N_driver/N_driven)/n, where D is ground-wheel diameter, n the cells per plate; for D = 400 mm and S = 10 cm, cells and sprocket teeth are chosen to suit groundnut.
   • Cell size: cell length ≈ 1.1–1.3 × seed length, depth ≈ seed thickness, so one seed enters per cell.
   • Shaft and chain: torque from metering resistance plus agitator; chain selected from standard tables.
   • Push force: estimated from soil resistance of two furrow openers.
5. CAD model, drawings, bill of materials; Stage I report and oral.

Stage II (402053, Semester 8)

1. Fabrication: MS square-tube frame (welded), 400 mm ground wheel with lugs, bearings, sprockets, hopper in GI sheet, shoe-type furrow openers, chain covering device.
2. Plates: printed in PLA and PETG with 40–60% infill; cell edges checked with a gauge; two plates per crop to compare filaments.
3. Laboratory test: grease-coated belt pulled at 2, 3 and 4 km/h; 250 seed spacings recorded per run, three replications.
4. Field test: 0.1 ha strip; plots with the drill and with traditional sowing; spacing measured over 10 m in each row after emergence.

Performance indices (Kachman and Smith method)

• Missing index: spacings > 1.5 × theoretical spacing.
• Multiple index: spacings ≤ 0.5 × theoretical spacing.
• Quality of feed index = 100 − missing − multiple.
• Precision: coefficient of variation of spacings within the acceptable band.
• Seed damage %, effective field capacity (ha/h), field efficiency, push force (spring balance or load cell).

Analysis

Two-way ANOVA (speed × plate material) on quality-of-feed index; t-test of seed rate between drill and traditional sowing; cost of operation per hectare versus hired dibbling.

Timeline (Stage II, 14 weeks)