Soil adjacent to an elongated furrow is irrigated by flowing the water from a header into and along the furrow, and erosion of the furrow is reduced and infiltration into the soil is increased by dissolving solid flocculant in the header or in the furrow into the water. The solid flocculant is best provided as a block of particulate flocculant bonded by a water-soluble wax. The irrigation process is best conducted on a cyclic basis with the solid flocculant being removed from the header or furrow during the cycle and with the supply of water being continued so that there is subsequent run-off of water from the furrow.
