Development and evaluation of retrofit foldable seeding attachment for single-pass harvesting cum sowing under conservation tillage

In rice–wheat cropping systems, combine harvesting generates substantial residue, delaying subsequent sowing operation and increasing labor and operational costs. To address these challenges under conservation tillage, a retrofit foldable seeding attachment was developed for combine harvesters to enable simultaneous harvesting cum sowing. The attachment includes an electronic seed metering unit, adjustable furrow openers, a hydraulic lifting system, and a foldable frame for ease of transport and manoeuvring in fragmented fields. The seed metering unit, designed considering the physical and engineering properties of green gram (MH 421), was evaluated under laboratory conditions for uniform seed delivery and spacing. Three furrow openers—single disc, double disc, and inverted T-type with rolling coulter—were tested in a soil bin to assess draft force and straw-cutting efficiency. The inverted T-type furrow opener with rolling coulter showed the highest straw-cutting efficiency (84.5%) at a speed of 1.5 km/h and was selected for field trials. Field performance was evaluated at three forward speeds (1.5, 2.0 and 2.5 km/h) and three straw cutting heights (20, 25 and 30 cm). The optimal performance was obtained at 1.5 km/h forward speed and a 20 cm straw-cutting height, where the attachment recorded a seed placement index of 85.29%, a mean seed spacing of 10.4 cm, a germination percentage of 94.23%, and a missing index of 3.2%. The attachment demonstrated a field capacity of 0.51 ha/h, field efficiency of 78.95%, and fuel consumption of 18.2 L/h, promoting timely crop establishment and eliminating the need for separate sowing operations.