Water management of paddy rice cultivation in Niigata


 Niigata is a representative rice cultivation area in Japan, and “Koshihikari” is mainly produced here. There are enough water resources except in the mountainous area, and thus, droughts are rare. There are more than 200 reservoirs in this prefecture, to prepare for droughts, but the paddies, which are the supply target, only make up 10% of all paddies. The soils in west Itoigawa and east Niigata are slightly different, as the soil in Itoigawa tends to be coarse and drains water away, since the plain area in Itoigawa is rather small. Still, the water drains at a rate of about 15 mm a day. From a standpoint of holding fertilizers and agricultural chemicals, about 10 mm a day is suitable as a sense of the person in charge. Meanwhile, there the mountain in Itoigawa provides a plentiful supply of water, and the soil is well drained. Conversely, in Niigata, although water resources are less plentiful than in Itoigawa, the soil is clayish and retains water, balancing the water resource and soil quality. Soil is generally coarse in the mountains and fine in plains. Thus, in the mountains, water sometimes drains at a rate of 80 mm a day, even in Niigata.
 A primary characteristic of this area is that local farmers fill paddies with water faster than is done under intermittent irrigation. Although intermittent irrigation is done after the midseason drainage period in many places, in Niigata the water level is set to 30 mm before all the water is drained, including during the period around heading stage.
 The Foehn phenomenon occurs in the summer in this area, causing serious damage due to high temperatures in recent years; therefore, quickly filling paddies to be one of the measures to meet them. It means that various methods of dealing with heat are now being examined. Incidentally, in the Toyama prefecture, which is next to Niigata, water levels are kept high during the heading stage, as a measure against cadmium pollution.