Study of the Mathematical Models for Operation of Liquid Fertilizer Application

Biogas from methane fermentation is anticipated for use as an alternative energy resource to fossil fuel. However, a problem persists related to treatment of wastewater generated in methane fermenters. Consequently, the wastewater must be processed additionally to reduce environmental load when released. The most important problem is the treatment raises the total running cost of fermenters. To lower this cost, application of the wastewater as liquid fertilizer in paddy fields without the treatment has been studied. However, in rice cropping, the suitable periods for application are limited. This study is intended to produce models for estimating working hours in each paddy field to construct an effective operation plan of a slurry injector for liquid fertilizer. Working times in the paddy fields were investigated for two cases of liquid fertilizer application: Nantan and Yamaga. Two simple models can be constructed; which model should be used can be determined according to the paddy field shape.