Soil opener for driving through soil in a direction of travel, the soil opener comprising: a leg; and first and second soil-cutting discs (20,1) mounted on the leg, the first soil-cutting disc defining a first wheel axis and the second soil-cutting disc defining a second wheel axis; wherein the first soil-cutting disc has a first soil-engaging surface (20") inclined at a first angle to a perpendicular to the soil surface when viewed along the direction of travel, the first angle being greater than zero; and the second soil-cutting disc comprises a rotating disc and has a second soil-engaging surface (1") that faces away from, and in a substantially opposite direction to, the first soil-engaging surface (20"); wherein: both the first and second soil-cutting discs (20,1) are inclined to the same side of a perpendicular to the soil surface, wherein the second soil-cutting rotating disc lies parallel to the direction of travel when viewed along a perpendicular to the soil surface and with the second soil-engaging surface (1") being inclined at a third angle to a perpendicular to the soil surface when viewed along the direction of travel, the third angle being greater than zero and in the same sense as and greater than said first angle; and wherein the first soil-cutting disc sits within the circumference of the second soil-cutting rotating disc when viewed transversely to the direction of travel and parallel to the soil surface, with the first soil-engaging surface (20") being additionally inclined at a second angle to the direction of travel when viewed along a perpendicular to the soil surface, the second angle being greater than zero, whereby the first and second soil-cutting discs (20,1) are mounted on the leg so as to be substantially coincident in the direction of travel with the first and second soil-cutting discs (20,1) being inclined relative to one another such that the gap between the first and second soil-cutting discs (20,1) at a point below and ahead of the first and second wheel axes (1', 20') is smaller than the gap at a point behind and above the first and second wheel axes (1',20'). a leg; and first and second soil-cutting discs (20,1) mounted on the leg, the first soil-cutting disc defining a first wheel axis and the second soil-cutting disc defining a second wheel axis; wherein the first soil-cutting disc has a first soil-engaging surface (20") inclined at a first angle to a perpendicular to the soil surface when viewed along the direction of travel, the first angle being greater than zero; and the second soil-cutting disc comprises a rotating disc and has a second soil-engaging surface (1") that faces away from, and in a substantially opposite direction to, the first soil-engaging surface (20"); wherein: both the first and second soil-cutting discs (20,1) are inclined to the same side of a perpendicular to the soil surface, wherein the second soil-cutting rotating disc lies parallel to the direction of travel when viewed along a perpendicular to the soil surface and with the second soil-engaging surface (1") being inclined at a third angle to a perpendicular to the soil surface when viewed along the direction of travel, the third angle being greater than zero and in the same sense as and greater than said first angle; and wherein the first soil-cutting disc sits within the circumference of the second soil-cutting rotating disc when viewed transversely to the direction of travel and parallel to the soil surface, with the first soil-engaging surface (20") being additionally inclined at a second angle to the direction of travel when viewed along a perpendicular to the soil surface, the second angle being greater than zero, whereby the first and second soil-cutting discs (20,1) are mounted on the leg so as to be substantially coincident in the direction of travel with the first and second soil-cutting discs (20,1) being inclined relative to one another such that the gap between the first and second soil-cutting discs (20,1) at a point below and ahead of the first and second wheel axes (1', 20') is smaller than the gap at a point behind and above the first and second wheel axes (1',20'). both the first and second soil-cutting discs (20,1) are inclined to the same side of a perpendicular to the soil surface, wherein the second soil-cutting rotating disc lies parallel to the direction of travel when viewed along a perpendicular to the soil surface and with the second soil-engaging surface (1") being inclined at a third angle to a perpendicular to the soil surface when viewed along the direction of travel, the third angle being greater than zero and in the same sense as and greater than said first angle; and wherein the first soil-cutting disc sits within the circumference of the second soil-cutting rotating disc when viewed transversely to the direction of travel and parallel to the soil surface, with the first soil-engaging surface (20") being additionally inclined at a second angle to the direction of travel when viewed along a perpendicular to the soil surface, the second angle being greater than zero, whereby the first and second soil-cutting discs (20,1) are mounted on the leg so as to be substantially coincident in the direction of travel with the first and second soil-cutting discs (20,1) being inclined relative to one another such that the gap between the first and second soil-cutting discs (20,1) at a point below and ahead of the first and second wheel axes (1', 20') is smaller than the gap at a point behind and above the first and second wheel axes (1',20').