PhD

Sowing accounts for 18.0 per cent of labour utilization in India which indicates
that sowing of seeds is a highly labour-intensive operation. The major constraint in
sowing is the non-availability of labour in time, especially, during peak periods of
sowing and harvesting. Traditional methods of sowing involve sowing excess seeds
and thinning the plants to obtain the desired plant population at uniform plant spacing.
For obtaining high yield, it is very essential to drop the desired number of seeds in rows
maintaining accurate seed rate and seed spacing during metering. Among different
sowing techniques, precision sowing is the preferred method, since it provides accurate
spacing of single seeds in the row with proper planting depth and creating a uniform
germination environment for each seed.
In conventional planters the metering mechanism is usually driven by a ground
wheel, to maintain the seed rate, irrespective of the forward speed. The speed ratio
between the ground wheel and seed metering mechanism could not be maintained due
to the power transmission loss, resulting in a reduction in uniformity of seed
distribution. To solve the above problem, an alternative method of driving the metering
mechanism with a 24 V DC motor was identified in this study. The metering unit was
synchronized with the forward speed with the help of an encoder, Arduino Nano and
crank-rocker linkage.
The performance of the seed-metering device of a multi crop precision planter
was investigated under laboratory and field conditions to optimise the design and
operating parameters for groundnut, maize, cowpea and okra seed planting. The effect
of operational speed of the metering mechanism disc, forward speed and cell size were
evaluated by examining the mean seed spacing, precision in spacing (coefficient of
variation), miss index, multiple index, and highest quality of feed index. For picking
single seed, the planter disc had a single cell of size 12 mm, 10 mm, 9 mm and 8 mm
in diameter for groundnut, maize, cowpea and okra respectively. The metering disc
peripheral speed was operated 0.86 m s-1
(165 rpm).
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It was observed that the optimum forward speed was 1.5, 2.5, 1.5 and 3.0 km h1
for groundnut, maize, cowpea and okra when the metering disc peripheral speed was
at 0.86 m s-1
(165 rpm) and cell size was 10 % more than maximum seed dimension.
However, there was conclusive statistical evidence to identify a single value of disc
speed and cell size. Lower missing index were observed at highest cell size and lowest
speed and low multiple index at low cell size and highest speeds. The metering
mechanism with a peripheral speed of 0.86 m s-1
(165 rpm), and a 10 % more than
maximum seed dimension for groundnut produced superior results with a miss index 2
%, multiple index 2 %, precision index 9 % and maximum value of quality of feed index
95 %. For maize, the minimum values of miss index 1 %, multiple index 2 %, precision
index 9 % and maximum value of quality of feed index 94.5 % were observed for
metering disc peripheral speed of 0.86 m s-1
and 10 % more than maximum seed
dimension. For cowpea, the minimum values of miss index 1.5 %, multiple index 4 %,
precision index 8.5 % and maximum value of quality of feed index 93.5 % were
observed for metering disc peripheral speed of 0.86 m s
-1
and 10 % more than maximum
of seed dimension. For okra, the minimum values of miss index 1 %, multiple index 3
%, precision index 8 % and maximum value of quality of feed index 93.5 % were
observed for metering disc peripheral speed of 0.86 m·s
-1
and 10 % more than
maximum of seed dimension.
Based on the optimised operational parameters, performance indices of the multi
crop precision planter was determined under field condition by measuring the
distribution of seeds and its spacing. The minimum values of miss index 6 %, multiple
index 4 %, precision index 12 % and maximum value of quality of feed index 87 %,
emergence plant population index 93.82 % and average mean seed spacing 17.79 cm
were observed for groundnut. For maize, the minimum values of miss index 5 %,
multiple index 4 %, precision index 13 % and maximum value of quality of feed index
87 %, emergence index 94.53 % and average mean seed spacing 27.39 cm were
observed. For cowpea, the minimum values of miss index 5 %, multiple index 5 %,
precision index 14 % and maximum value of quality of feed index 86 %, emergence
index 95.82 % and average mean seed spacing 17.58 cm were observed. For okra, the
minimum values of miss index 5 %, multiple index 4 %, precision index 15 % and
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maximum value of quality of feed index 87 %, emergence index 95 % and average mean
seed spacing 32.82 cm were observed.
The maximum field capacity and efficiency were 0.54 ha hr-1
and 88 %
respectively. The savings in cost and time for mechanical planting was about 89.1 %
and 99.27 % compared to manual planting. Based on the field performance evaluation,
it is concluded that the developed tractor drawn multi-crop precision planter is
economical and efficient for planting different seeds.