If you ever wonder if the money you spend on graphite, or the time and mess of putting it in each hopper box is worth it, here's an example which illustrates how the substance can act as a lubricate, affecting how soybean seed throws through a drill or planter.
I visited a farmer who was drilling soybeans with a split-row planter on 15-inch rows. His target population was 165,000 to 170,000 seed per acre. After he fills boxes, he adds graphite on top. Naturally, it takes some time for the graphite material to work its way down through the seed in the box.
For the first half hour, his monitor showed from 159,000 to 161,000 seeds per acre. A little digging confirmed that each row was working and spacing seed about as he wanted. The populations just weren't quite up to where he was looking for.
Then the population kicked up to about 167,000 to 169,000. From then on, he said, it ran in that narrow range most of the time. If seed boxes got about empty, and he was planting seed where more of the graphite was settled, the rate would increase slightly. That seed was fully coated with graphite.
Once the graphite was in the system, even when he refilled the planter, the seeding rate according to the monitor did not change. It hung around 167,000 to 169,000 seeds per acre. He was using a Kinze planter with Kinze bean metering cups to plant.
The value of graphite in helping seed flow more uniformly dates back to when farmers primarily had switched to no-till drills. It also helped in those situations. Drill metering systems aren't as precise in most instances anyway. It's one reason many have switched back to planters, typically in 15-inch rows so they can still capture part of the benefit of narrow rows for soybeans. Estimates say that you capture about two-thirds of the yield increase for narrow rows going from 30-inch rows down to 15-inch rows. The next step down to 7-inch rows, a common drill width, only brings in about another one-third increase in yield.
Many farmers are deciding they can live with a two-thirds increase, with the trade-off being more accurate seed drop and spacing, and usually more uniform depth placement as well.
The example here shows that either way, graphite needs to be part of the system.