Abstract: A liquid ejection head includes a print element substrate including multiple ejection openings, pressure chambers, a common flow path, and pumps, the pumps being configured to circulate liquid between the common flow path and the pressure chamber; and a flow path member laminated to the print element substrate. The flow path member includes a supply flow path and a collection flow path, the supply flow path being configured to supply liquid to the print element substrate, and the collection flow path being configured to collect liquid that is not ejected. The supply flow path and the collection flow path have liquid connection with the same common flow path. A circulating pump generates a flow of liquid flowing in an order of the supply flow path, the common flow path, and the collection flow path, the circulating pump being provided at a position different from the print element substrate.

Abstract: An object of the present invention is to make it possible to easily evaluate silage fermentation quality on site or the like. In one embodiment of the present invention, a gas generated from silage is applied to a surface stress sensor, and the amount of either one of organic acids and nitrogen-containing compounds contained in the silage is determined. The surface stress sensor can detect trace components in a gas by a simple device configuration and in simple procedures. Therefore, by utilizing the fact that relationship between the content of these components and the fermentation quality is known, the evaluation of fermentation quality can be easily realized by the above measurement.