Abstract
For the sustainable development in the agricultural sector, Japan is promoting the expansion of the area of conventional agriculture, i.e. environmental conservation agriculture that does not use pesticides or chemical fertilisers. In the paddy fields of the Hiki Hills region in northern Saitama Prefecture, reservoirs are formed at the head of eroded valleys to efficiently store rainwater and use it as a source of irrigation water for rice cultivation. The water storage system and the geographical location of the valley prevent the inflow of pesticides and chemical fertilisers. Paddy fields using the reservoirs are called 'yatsu-fields' in the region, and the farming form of yatsufields is known as yatsunuma agriculture. Yatsunuma agriculture was selected as a Japanese Nationally Important Agricultural Heritage Systems（J-NIAS）in 2023.
However, paddy rice cultivation in valley rice paddies relies heavily on experience, as it cannot be controlled with pesticides and chemical fertilisers as in conventional cultivation. As a result, the retention rate of new farmers is low. In addition, Japanese farmers are rapidly ageing, and the amount of abandoned land in yatsuta fields is increasing year by year.
Remote sensing (RS) has often been used in the agricultural sector, but has been limited to acquiring images at regional scales due to image scale limitations. The development of unmanned aerial vehicles (UAVs) has made it possible to acquire imagery at higher spatio-temporal resolutions than regional scales.
