Abstract
To solve the problems that occur when farmers overuse chemical fertilizers, it is necessary to develop rapid and efficient portable measurement systems for the detection and quantification of nitrogen (N), phosphorus (P), and potassium (K) in soil. Challenges arise from the use of currently available portable instruments which only have a few channels, namely measurement and the reference channels. We report on a home-built, multichannel, optoelectronic measurement system with automatically switching light sources for the detection of N, P, K content in soil samples. This optoelectronic measurement system consists of joint LED light sources with peak emission wavelengths of 405 nm, 660 nm, and 515 nm, a photodiode array, a circuit board with a microcontroller unit (MCU), and a liquid-crystal display (LCD) touch screen. The straightforward principle for rapid detection of the extractable nutrients (N, P, K) was well-established, and characterization of the designed measurement system was done. Using this multi-channel measurement system, available nutrients extracted from six soil samples could be measured simultaneously. The absorbance compensation, concentration calibration, and nutrition measurements were performed automatically to achieve high consistency across six channels. The experimental results showed that the cumulative relative standard deviations of 1.22%, 1.27%, and 1.00% were obtained from six channels with known concentrations of standard solutions, respectively. The coefficients of correlation for the detection of extracted nutrients of N, P, K content in soil samples using both the proposed method and conventional lab-based method were 0.9010, 0.9471, and 0.8923, respectively. Experimental results show that this optoelectronic measurement system can perform the measurement of N, P, K contents of six soil samples simultaneously and may be used as an actual tool in determining nutrients in soil samples with an improvement in detection efficiency.
Highlights
There are more than 13 essential nutrients that are supplied by soil for crop growth
We demonstrated that the optoelectronic measurement system based on joint LED
Light sources with a multichannel cuvette holder can be used to measure the concentration of N, P, K
Summary
There are more than 13 essential nutrients that are supplied by soil for crop growth. Not all soils are sufficiently fertile to provide balanced nourishment [1]. For this reason, the appropriate fertilizers should be applied to soil when specific nutrients are deficient such that it may result in reduced crop yield. It is known that fertilizer application is one of the most effective ways to increase crop production [2,3,4]. The average amount of urea in China is reported to be 180 kg/ha to obtain a high yield in the majority of crops [5]. Fertilizer applications exceeding crop requirements can pollute groundwater and stream water [6].
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