In-situ automatic measuring device for ammonia volatilization in farmland

Excessive application of nitrogen fertilizer has caused the reduction of nitrogen fertilizer utilization efficiency, resource waste and environmental problems in our country. There are disadvantages of long sampling and heavy workload using the traditional methods of acid absorption and box method for farmland ammonia volatilization measurement. In order to meet the application needs for on-line automatic measurement of ammonia volatilization in farmland, an in-situ automatic measurement device for ammonia volatilization was designed combined with laser spectroscopy technology. The main body of the measurement device is an integrated sampling box, with the advantages of long optical path measurement, heat resistance and corrosion resistance. The control circuit of the sampling box used ARM as the main controller for environmental data monitoring, automatic opening and closing of the cover and lens temperature controlling. The ammonia volatilization results were analyzed by the data acquisition and processing system after the laser passed through the sampling box to obtain ammonia spectroscopy signal. The device was used for observation at Fengqiu Ecological Station, CAS. The results showed that the ammonia volatilization rose rapidly after 90 minutes for nitrogen fertilizer applying, and it decreased gradually to a low value after 270 minutes. According to the experimental results, the continuous measurement time for cover closing can be set to 3 minutes, and the cover opening time can be set to 3 to 5 minutes. The working performance of the automatic measurement device was verified through these experiments, with the advantages of low power consumption, high measurement sensitivity, and no gas sampling. It realizes insitu automatic measurement for ammonia volatilization in farmland with the natural respiration condition of the soil.