Abstract
Because of recent technological development in digital camera miniaturization, it is now possible to acquire aerial photographs with a small balloon. However, there are few reports in Japan concerning such balloons and few field surveys of poor plant growth in wheat fields that were converted from paddy fields. Thus, we studied image analysis methods for aerial photography and examined the usefulness of the photography in the field survey and data analysis of wheat fields managed by a large-scale agricultural corporation. Aerial images were obtained with a compact digital camera attached to a small helium gas balloon measuring 1.8 m in length and 0.64 m3 in volume. Soil moisture content, leaf color index, plant height, ear number, and grain yield were determined. In the image analysis, topographical correction of aerial images, wheat vegetation rate, and areas with wet soil was conducted with graphics software. Birds’ eye view photographs acquired from a height of approximately 180 m facilitated the selection of fields to be studied because plant growth outline in a wide area could be compared. Vertical photographs of one field taken from a height of 117 m expedited the determination of sampling positions and enabled us to gain a perspective of the survey. The image analysis also simplified plant growth categorization and the analysis of the causes of poor plant growth. The causes were found to be high soil moisture content, increased soil hardness, and small relative field height. Soil color intensity in the aerial photographs enabled evaluation of the effectiveness of drainage measures. In conclusion, the small-balloon photography system is an effective tool to improve the precision of field survey and data analysis.
