Fertigation

Bindacall Brooks, Winter Gardening in the Maritime Northwest, Sasquatch Books, 1989, is especially good on this topic.

Fertilizing, Fertigating, and Foliar Spraying In our heavily leached region, almost no soil is naturally rich.

while fertilizers, manures, and potent composts mainly improve the topsoil.

But the water-wise gardener must get nutrition down deep, where the soil stays damp through the summer.