A tractor equiped with blades mixes volcanic ash on the
surface of this field with the underlying soil in San Marcelino,
Philippines. This helps reduce the amount of ash that can be
stirred up by wind and improves the mulching effect of the ash
in soil. Mixing the ash with soil also prevents the development
of a hardened crust of ash on the ground; such a crust can increase
the surface runoff during rainfall, which can lead to increased
erosion along furrows, gullies and stream channels.
A variety of factors determine the effects of ash on
agricultural land, including the thickness of the ash
deposit, the type of crop that is being grown, and the
maturity of the crop at the time of the ashfall. Also,
livestock can become ill and die from ingesting
flourine-rich ash.
|