Construction of VSSD: The 2WT-based VSSD was fabricated with locally available materials such as MS angle, solid bar, MS sheet, ball bearing etc. The main functional parts of the planter were: seed box (having six fluted-roller type seed meters mounted with a shaft plus the same number of vertical disk seed meters; the fertilizer box with fluted roller type metering mechanism (four flutes); the toolbar frame; depth controller-cum-press roller; driving seat for transportation; furrow opener, etc. The VSSD was powered by 8.95 to 11.9 kW Dongfeng, or Saifeng 2WT but could be used with any other 2WT with similar power rating and hitching arrangement. The Dongfeng or Saifeng 2WT have different but suitable hitching points to attach with the VSSD.
Versatile Strip Seed Drill Design: The VSSD is designed with the capability of seeding using a fluted roller type seed meter for high density seeding and/or using a vertical disk for spaced planting and with fertilizer meters for the drilling of granular-type fertilizers in a row. The net weight of the VSSD is 161 kg (excluding driving seat arrangement) and the overall dimensions are 1270 mm (length), 762 mm (width), and 840 mm (height). The furrow openers were designed with the capacity to separate seed and fertilizers while planting, and were bolted to the base of the rotary shaft cover of the VSSD. A pressing roller 1200 mm long with a diameter of 127 mm, made from a 2 mm iron sheet, is attached behind the furrow openers using a pair of arms. The VSSD is mounted on a toolbar, attached through side arms, and connecting the rods to the main handle of the 2WT. Seed and fertilizer boxes are mounted on top of the toolbar frame. The seed and fertilizer boxes have provisions for seeding and fertilizing up to six rows (200 mm row distance), and down to three rows (600 mm row distance). The maximum 46 numbers of tines could be attached with the rotary shaft. The 1200mm long cylindrical rotary shaft is operated by the 2WT at 475 or 550 rpm through a chain and gear mechanism. The power transmission chain box is located on the right side of the planter, with 28 teeth on the upper sprocket attached to the drive shaft, and 14 teeth on the lower sprocket attached to the rotary shaft. The rotary shaft and tines are covered by a metal sheet. The rotary shaft is designed with 23 pairs of tine holders to fix 46 tines. The settings of the tine holders and the tines on the rotary shaft, for various rowspacing crops. Each pair of tine holders should have one right and the other left, twisted, 160mm long, and 37mm width tine, with a 520 bend at the end so that the cutting edge tills up to about a 50mm width in the row. A total of six, fluted rollertype seed meters were fitted to the base of the seed box, and the same number of vertical seed meters were fitted to the front wall of the seed box. Depending on the level of precision in seed placement, either fluted roller type or vertical plate type seed meters can be chosen for seeding. Seed rate can be adjusted by sprocket size in the case of vertical plate meters. Sprocket sizes range from 10 to 40 teeth, providing five settings for seed rate and seed size. For the fluted roller seed meter, seed rate is varied by adjusting the length of the fluted rollers using a handle. By fitting seed meters with 4, 8, or 16 flutes, delivery of differentsized seed can be regulated. The fertilizer box is made from the same iron sheet and has the same external dimensions as the seed box. The fertilizer box is fitted with six fluted rollertype meters, with eight or four deeper flutes. Seed and fertilizer meters are attached to separate shafts. The power for the fertilizer meters comes from the 2WT differential shaft, through a chain, driven by a 19tooth sprocket, and is relayed to the fertilizer meter shaft through a chain and sprocket. Seed and fertilizer delivery tubes made as 27mm in diameter, clear polypropylene pipes, are attached behind the furrow opener. A pressing roller, 1200 mm long with a 127mm diameter is attached behind the furrow openers by a pair of arms, 560 mm long.
Initial Testing of VSSD: The VSSD was initially tested for up to six rows of strip planting with six pairs of small “L” shaped blades attached in rows. Eight and four-flute types of seed and fertilizer meters, respectively, were used to successfully regulate seeds and fertilizers in the case of continuous seed delivery of wheat, lentil, chickpea, mustard, etc., and basal fertilizer banding in the same strip. Seed and fertilizer in the soil were mostly consolidated by the press roller in a single pass operation. The seeding and fertilizing depth was maintained in a range, from 20 to 60 mm. The verticaltype seed meters with three different apertures were successfully used for the precision planting of maize, rice, and okra seeds.
Seed Calibration: Seed rate was calibrated over a 20m travel distance with a 120mm sowing width. This procedure was used to calibrate the VSSD for a range of crop species before performing the test planting in fields. Data on labor requirement, operational time, time loss, and field capacity were recorded during the field test. The time losses due to turning, clogging and operators’ personal needs were also recorded. The rate of area coverage (field capacity) during planting was also determined for the VSSD while establishing various crops.
Soil Types and Agro-Ecology of Initial Field Trials of VSSD: Initial field trials were conducted at Savar upazila, Dhaka District and Baliakandi upazila, Rajbari District in Bangladesh; and Chaibasa District of Jharkhand State in India from June to December, 2013. The Savar site is under Agro Ecological Zone (AEZ)8 (young Brammaputra and Jamuna floodplain) with silty clay loam soil. The Baliakandi site is under AEZ11 (low Ganges river floodplain) and the soil type is sandy loam to loamy; and the soil type of Chaibasa is loamy to clay.
Initial Field Trials of VSSD: The average field size of the initial trials was 900 m2 in Savar, 1200 m2 in Baliakandi, and 2250 m2 in Chaibasa. The initial field trials of the VSSD were done by attaching it to a 11.9 kW Dongfeng 2WT manufactured in China. The VSSD was used to seed rice, wheat (Triticum aestivum L.), maize (Zea mays), lentil (Lens culinaris), chickpea (Cicer arietinum), mustard (Brassica napus L.), okra (Abelmoschus esculentus L. Moench), and jute (Corchorus olitorius); and basal fertilizers (granular form) of diammonium phosphate and triple superphosphate were banded at the time of crop establishment.
Multi Locational on Farm Evaluation Trials: In 2013–2014, a total of six multilocational onfarm evaluation trials were conducted for the planting of wheat seed. In 2014–2015, similar trials were repeated to establish wheat, mustard, and lentil crops in the same area. All multilocational onfarm evaluation trials plots were located at Baliakandi upazila in the Rajbari District. The average plot sizes of the multilocational onfarm trials were 1220 to 1340 m2 and the tillage treatments were:
- SP = Locally hired VSSD was used in dry land to open 20to 50mm deep and 40to 50mm wide planting strips; seed and fertilizers were placed in rows, either by a verticaltype seed meters for spaced planting (1 seed of maize and 3–4 seeds of rice per hill) or a fluted rollertype seed meter for high density seeding (for wheat, mustard, jute, and lentil) in a single pass operation.
- CT = Land preparation for crop establishment was done by locally hired 2WT using 2 to 4 full rotary tillage passes in dry land followed by 1 to 2 leveling operations. The tillage depth of CT was 45–55 mm. The seed and fertilizers were hand broadcast prior to final soil tillage and leveling.
VSSD Contract Planted Fields: A local service provider (LSP) offered contract planting using VSSD to establish wheat, lentil, jute, mustard crops on more than 70 farmers’ fields including several farmers who used the VSSD to make strips in untilled fields before establishing unpuddled transplanted rice during 2013–2014 and 2014–2015. The contracted land sizes were 850 to 4500 m2. Most of the farmers had retained rice residue at the height of 150–200 mm (equivalent to 1.5 t¨ ha´1), but no problem was encountered with use of the VSSD up to that level of retained residue. The VSSD was used to establish crops in half of the plots while CT was used to establish the same crops on the other half.
VSSD for Establishing Unpuddled Rice Seedling Transplanting: The VSSD was used to make 20–40 mm wide and 40–50 mm deep tilled strips (that preserved about 80% undisturbed soil) in undisturbed flat land: Following this, strip making ponded irrigation water to soak the soil for 24 h. Rice seedlings were transplanted manually in strips at 250 mm between rows and 200 mm between hills.
Data Collection
Data on Initial Field Trials of VSSD: Initial field trial data were collected from three quadrats (1 m2 each) and the averages of the three quadrats; for emergence of wheat, rice, chickpea, and maize. The field capacity of the VSSD for sowing and fuel consumption of initial field trials was collected from the whole plot at Savar, Dhaka, Bangladesh and converted to ha´1.
Multi Locational on Farm Evaluation Trials: Individual whole plot grain yield data on multilocational onfarm evaluation trials of SP and CT were collected from all trials and converted to ha´1.
VSSD Contract Planted Fields: Individual whole plot grain yield data supplied by LSP for VSSD and CT were collected from 43 farmers’ fields. The grain yield data reported ha´1 were for sundried grain yield at approximately 13%–15% moisture in the grain.
Data Analysis:
Initial Field Trials of VSSD: For the initial field trials of VSSD, effective field capacity, fuel consumption, and plant population were computed by Microsoft Excel 2010 to present mean and standard error (SE).
Multi Locational on Farm Evaluation Trials and Contracted VSSD Planting: Data were analyzed statistically using oneway analysis of variance (ANOVA) with Statistics 10 statistical software. Means were compared with least significant difference (LSD) test at p< 0.01 and p< 0.05.