Design and experiment of crop structural parameters automatic measurement system

The presented work aims to develop an automatic measurement system to collect crop parameters. In this paper, the structure parameters of land surface crops are considered. Crop structural parameters, such as leaf area index(LAI) and average leaf angle(ALA), are the main factors that can effect the solar energy re-assignment in the canopy. The traditional method to measure such parameters for crops, e.g. maize and wheat, is relied on the handy instrument, so it is difficulty to carry out the measurement on the large spatial region and on the long time series. An automatic measuring system which is designed on the basis of wireless sensors network(WSN) is present in this paper. The system is comprised of three types of node, i.e. two solar irradiance measurement nodes which are deployed beneath and above the canopy respectively, a sink node which is used to collect data from the measurement nodes, and the last type is a route node which is acted as a repeater of wireless communication. Canopy structural parameters can be calculated from the direct transmittance which is the ratio of sun radiation captured by the measurement node beneath and above the canopy on different sun altitude angles. Numeric simulation and the field preliminary validation results showed that the designed system could detect the directional canopy transmittance which is the basis to calculate the target parameters. And the further validation results revealed that the measured LAI values between LAI2000 instrument and our propose measurement system had high correlation coefficient and the calculated average leaf angles were very proximity to the theoretical values. So it is promising in the agriculture application to utilize the proposed system in measuring the crop structural parameters, and it can be an efficient way to measure such parameters in the large spatial region and on the long time series automatically.