Seed firmer

1. A seed firmer for pressing seeds into soil during planting, the seed firmer comprising:

a mount for attachment to a row unit of a planting machine; and

an arm defining a ground-facing surface having at least one point of contact with the ground, including a rearmost ground contact point with respect to a direction of forward travel during planting operation,

wherein the ground-facing surface has a transition section directly trailing a rearmost ground contact point, the transition section extending upwardly from the rearmost ground contact point with a radius no less than 25 mm,

wherein the mount includes a linkage having two parallel intermediate links rotatably coupled to the arm to provide vertical travel of the arm without changing the orientation of the arm,

wherein the mount further includes a first spring engaged with the linkage to bias the arm in a downward direction toward the ground, and

wherein one of the intermediate links has a selective sliding joint operable to enable the linkage to be selectively tripped to achieve an alternate, non-parallel relationship between the intermediate links upon encountering an obstacle during forward travel.

2. The seed firmer of claim 1 , wherein the rearmost ground contact point is the single lowest point of the ground-facing surface.

3. The seed firmer of claim 1 , wherein the ground-facing surface includes a flat section forward of the rearmost ground contact point.

4. The seed firmer of claim 1 , wherein the transition section extends upwardly from the rearmost ground contact point with a radius no less than 40 mm.

5. The seed firmer of claim 1 , wherein the transition section extends upwardly from the rearmost ground contact point with a radius no less than 60 mm.

6. The seed firmer of claim 1 , further comprising a second spring operable to bias the linkage such that the intermediate links are parallel, the second spring exhibiting an increasing bias force as the linkage is moved toward the alternate, non-parallel relationship.

7. The seed firmer of claim 1 , wherein the first spring is operable to bias the linkage such that the intermediate links are parallel, the first spring exhibiting an increasing bias force as the linkage is moved toward the alternate, non-parallel relationship.

8. The seed firmer of claim 1 , wherein the arm includes an overhang spaced rearward and above the rearmost ground contact point.

9. The seed firmer of claim 1 , wherein the transition section extends at least 3 mm above the rearmost ground contact point.

10. A seed firmer for pressing seeds into soil during planting, the seed firmer comprising:

an arm defining a ground-facing surface having at least one ground contact point for driving seeds into soil as the arm is moved across the soil;

a first link having a first end arranged for connection to a planting machine and a second end defining a first pivot connection with the arm such that the arm is pivotable relative to the first link about a first pivot axis; and

a second link having a first end arranged for connection to the planting machine and a second end defining a second pivot connection with the arm such that the arm is pivotable relative to the second link about a second pivot axis spaced from the first pivot axis,

wherein the arm is a non-compliant arm and the orientation of the ground-facing surface is controlled exclusively in relation to the first and second links.

11. The seed firmer of claim 10 , wherein a spacing distance between the first and second pivot axes is equal to a spacing distance between third and fourth pivot axes respectively provided at the first ends of the first and second links such that the first and second links are parallel intermediate links of a linkage for mounting the arm.

12. The seed firmer of claim 11 , wherein the first pivot connection is spaced further along the arm from the ground-facing surface than the second pivot connection, and wherein a first spring is extended between the first pivot connection and the first end of the second link, the first spring providing a bias force that increases as the ground-facing surface moves closer to the first ends of the first and second links.

13. The seed firmer of claim 12 , wherein one of the first and second links has a selective sliding joint operable to enable the linkage to be selectively tripped to achieve an alternate, non-parallel relationship between the first and second links upon encountering an obstacle during forward travel.

14. The seed firmer of claim 13 , further comprising a second spring operable to bias the linkage such that the first and second links are parallel, the second spring exhibiting an increasing bias force as the linkage is moved toward the alternate, non-parallel relationship.

15. The seed firmer of claim 13 , wherein the first spring is operable to bias the linkage such that the first and second links are parallel, the second spring exhibiting an increasing bias force as the linkage is moved toward the alternate, non-parallel relationship.

16. A seed firmer for pressing seeds into soil during planting, the seed firmer comprising:

an arm defining a ground-facing surface having at least one point of contact with the ground, including a rearmost ground contact point with respect to a direction of forward travel during planting operations,

wherein the ground-facing surface has a transition section directly trailing the rearmost ground contact point, the transition section extending upwardly from the rearmost ground contact point; and

wherein the ground-facing surface includes an overhang rearward of the transition section, the overhang including a ground-facing anti-rebound surface spaced above the rearmost ground contact point and arranged to limit upward travel of a seed flicked upward from the rearmost ground contact point.

17. The seed firmer of claim 16 , wherein the anti-rebound surface is formed as a continuous surface.

18. The seed firmer of claim 17 , wherein the anti-rebound surface is flat.