Modification: Though the initial test prototype was made carefully in FMP Engineering laboratory when the planter was produced largely, it was difficult to control uneven bending due to arc welding. Due to uneven base of the plates, small seeds were entering between the plate and base. So, six additional MS base plates were incorporated in the planter to produce uniform flat surface so that seed could not enter between base and plate. The diameter of the base plate was 127 mm with internal groove of 117 mm diameter. A bush was in built in the base plate with length, internal diameter and outer diameter of 30, 25 and 15 mm, respectively. It was found during the test that for sowing of wheat (120 kg/ha) the rpm of the plates have to increase. Based on this, the plates were tested and an additional pinion of 14 teeth was added by the side of the power taking pinion of 19 teeth. Three plates were redesigned and fabricated with aluminum. Opening of the seed cell was redesigned with higher right angle to make the groove steep enough to decrease the time delay for seed dispersing as much as possible between the seeds consecutively dropped from the groove. Thus the opening of the seed cell was more in the contact surface than the appearing surface of the plate. Thickness and diameter of plates were 5.5 and 115 mm, respectively. The numbers of seed cell at the periphery of the plate were 9 for large seed (maize), 32 for small seed (wheat, mung bean, lentil, jute, etc) and 11 for rice seed. Changing of inclination of the plate is needed to use same (32 seed cell) plates for different crops and to calibrate the planter for 10% more or less seed than the predefined rate. Hence provision of changing inclination was incorporated that was absent in the previous version. Before field testing, the planter was tested in laboratory with different seeds.
Laboratory test: After fabrication of the planter, it was tested in the divisional workshop for maize, wheat, mungbean, lentil and rice seed during 2011-12. Calibration was done with the modified planter and plates. To calibrate the machine the numbers of furrow opener was adjusted according to crop (example: 6 lines for wheat, rice, jute; 4 lines for lentil, mungbean and mustard; and 2 lines for maize). The planter was operated in 20m long field after setting poly bags with rubber band in the furrow opener. The following equation was used to calibrate the machine and check the capability of the planter to dispense required operating in a field for a specific distance.
Seed in Polybag (kg) = {Seed rate (kg/ha) Line to line distance (m) X Travel distance (m)}/10,000
To calculate the field efficiency of the planter, a field of 20 x 10 m was planted. The planting operation was performed longitudinally with a forward speed of 1.3 km/h. While planting this area, the effective operating times and the times spent to fill the seed hopper were recorded and using Equation 1 (Kepner, 1978) the field efficiency was calculated for the inclined plate planter.
e= 100 (Te/Tt) .......................... (1)
Where,
Te = effective operating time (min),
Tt= total time (min), and
e = field efficiency (%).
Effective field capacity was also calculated using
Equation 2 (Kepner, 1978).
Ce =WSe/1000 ...........................(2)
Where,
Ce= effective field capacity (ha/h),
W = implement effective width (m), and
S = forward speed (km/h).
To calculate the coefficient of uniformity of seed distribution, prepared land strip with measurements of 20 x 1.3 m was filled with a layer of fine soil of 50-mm thickness. Planting was performed on the strip at a speed of 1.3 km/h. An area of two rows with a length of one meter was randomly selected using a wooden frame in each replication. The planted seeds in this area were separated from the soil using a sieve. The coefficient of uniformity of seed distribution was computed using Equation 3 (Senapati et al., 1992).
Se= 100 {1-(Y/D)} ....................(3)
Where,
Se = coefficient of seed distribution uniformity (%),
Y = average numerical deviation of number of
plants per meter length of row from average
number of plants per meter run, and
D = average number of plants per meter length of row.
To measure plant depth uniformity, planted seeds were irrigated gently and adequate time was provided for seedling emergence. Once emerged, seedlings were cut at the soil surface. A part of the stem that was inside the soil (from soil surface to seed remnants on the root) was taken out and its length was measured. This length was considered as a criterion to compare the seeding depth of the planter. 20 samples were taken, and the coefficient of planting depth uniformity was calculated using Equation 4 (Senapati et al., 1992).
Sd= 100 {1-(Yd/Dd) ....................... (4)
Where,
Sd= coefficient of planting depth uniformity (%),
Yd = average numerical deviation of depth of seeds planted from pre-set planting depth and
Dd= average depth of seeds planted.
Field performance test: Field performance test of the planter was conducted in divisional experimental plot of BARI, Gazipur, farmers’ field of Pabna and Barisal during 2011-12. In Gazipur, Inclined plate planter was tested for maize (BARI hybrid maize-7) in clay loam soil at 23% moisture content. The experiment was conducted with four treatments: T1= Bed planting with inclined plate, T2= Inclined plate planter with full tillage, T3= Inclined plate plates with strip tillage and T4= Conventional hand planting. All the treatments were replicated thrice with RCB design. Date of sowing was 24 January 2012 and the harvesting date was 17 June 2012. Spacing of maize seed was 60 x 20 cm. In Pabna, wheat (Bijoy) was sown in farmer's field with inclined plate planter on 2 December 2012 and harvested on 12 April 2012. In Barisal, the inclined plate planter was used in the farmer's field for sowing maize (BARI maize 9), wheat (BARI Gom 26) and mungbean (BARI mung 6). Irrigation, fertilizing, weeding and other intercultural operations were done timely. Data of yield and yield contributing character of maize for different tillage and sowing methods were collected from Gazipur. Collected data were analyzed with MSTAT statistical tool.