Design, development and evaluation of a variable rate applicator for real time application of fertilizer
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Date
2020
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Punjab Agricultural University, Ludhiana
Abstract
There is a strong need to avoid use of excessive N as it is unlikely to be effective in
increasing crop yields because of its diminishing returns. Therefore, a study was conducted to
design and develop a variable rate fertilizer applicator to detect real time deficiency of
nitrogen in the field and applying it as per requirement of the crop. To design and develop
variable rate applicator, fluted roller type metering mechanism was selected due to having
more uniformity than spinner disc type applicator. Suitable nitrogen (N) sensor i.e.
Greenseeker was selected for the development of applicator. The microcontroller system was
developed and PWM valve was used to vary the rotational speed of hydraulic motor resulting
variation in the rotation of metering mechanism shaft. Field performance of the developed
machine was measured at different levels of nitrogen (kg/ha), height (cm) of sensor from the
crop canopy and at different growth stages of the crop. Fluted roller type metering mechanism
was selected having lesser variation (CV ranging from 6.0 to 8.0 %) in fertilizer rate applied
as compared to the spinner disc type fertilizer applicator having CV ranging from 20.0-50.0
%. Fertilizer rate at 10 rpm of metering mechanism shaft was minimum i.e. 15.18 kg/ha and
was maximum 54.38 kg/ha at 40 rpm of the shaft speed. Speed of shaft of metering
mechanism changed from 0 to 40 rpm when NDVI was changing from 0.75 to 0.35. The
response time of the control system to apply fertilizer in the field was within the range of 6.45
to 7.81 s. Applied fertilizer by using developed variable rate applicator at different growth
stages of the rice crop at 40, 60 and 80 DAT indicated that when fertilizer rate is increasing
from N1 to N4, NDVI is increasing from 0.49 to 0.69. Hence, shaft speed is decreasing
from 27 to 7 rpm to apply the fertilizer rate 35.47 to 9.00 kg/ha respectively. Total fertilizer
applied by variable rate applicator was 122.32 kg/ha instead of 225 kg/ha as recommended by
the university resulting 45% saving in fertilizer by using developed variable rate applicator.
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Citation
Mirzakhaninafchi, Hasan (2020). Design, development and evaluation of a variable rate applicator for real time application of fertilizer (Unpublished Ph.D. Dissertation). Punjab Agricultural University, Ludhiana, Punjab, India.