Establishment of comprehensive drainage technologies for improving field drainage
2007
Kitagawa, I.(Hokkaido. Central Agricultural Experiment Station, Naganuma (Japan))
In Hokkaido, 48.6% of agricultural land requires drainage improvement. The actual area in Hokkaido where underdrains have been installed is equal to the area with poor drainage. However, the area where underdrains have been installed within the past 30 years is half of the necessary area. Redevelopment of underdrains is being done mainly in paddy fields and the field zone. Despite this, the total area where underdrain durability has been exceeded is on the increase. This makes it necessary to establish countermeasures to restore drainage function. To solve this problem we constructed an underdrain that significantly improves field drainage. Conventional drainage improvement has focused on the individual underdrain Conventional underdrain design attaches high value to drainage discharge. Increases in drainage discharge have been accomplished by narrowing the underdrain interval. However, there are drainage problems that cannot be solved by increasing discharge. Even from the underdrain subsoil improvements that enhance soil physics are necessary. To solve this problem it is necessary to develop comprehensive drainage technologies that combine subsoil improvement with a consideration of soil physics. This study makes clear the following. First, I determine the factors decreasing underdrain function. Then, I lay out plans to improve underdrain function and develop new subsoil improvement technologies. I also identify soil classifications that can benefit from the combination of drainage improvement technologies with subsoil improvement. This is determined by examining the relationship between soil physics and drainage status for the various soil classifications.
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