Gerald Holmes, California Polytechnic State University at San Luis Obispo, Bugwood.org
Last fall, I helped two producers establish cover crop plots. Using 2 different no-till drills, we filled seed hoppers, set seeding rates, planted out the field, vacuumed the seed boxes and then started again. Working to set seeding rates, we noted that the opening slide on the seed metering cups never responded uniformly.
Due to small seed size, the producers wanted to ensure planting accuracy. As we changed settings, we discovered that some metering units moved evenly, others moved suddenly and others didn‟t move at all. This affected seeding rates dramatically. Over the course of planting, the effect would not have been noticed but it would be in the affect of stand establishment.
To correct the variable opening on the seed cups, we set the seed setting to zero and then moved the setting to the recommended number. Still, we had problems with unevenness in opening width. Next, we tried moving the setting from zero to the maximum, then back to zero and then to our desired setting. Still, we had significant differences in our opening size. The end result was an attempt to estimate a setting and opening that we hoped would get the proper amount of seed in the ground. The producers planned to recondition their drills this winter. So what kind of shape is your drill in?
Another area of concern when planting small seeded crops is the condition of double disk openers. When wear occurs, the disks do not touch, creating a gap. The gap can be compensated for by planting larger seeds at a deeper depth. But when seeding ¼ inch, the gap causes the seed to fall directly on top of the soil and poor stand establishment results. Take time now to check the condition of your seed openers. Owners manuals provide guidelines on suggested diameters of these disks and recommend at what diameter the disks should be replaced.
Once you have reconditioned your drill, consider conducting a seeding rate calibration to ensure you are placing the proper number of seeds when you are planting. How often have you finished planting and ended up with too much leftover seed or suddenly discovered you ran out of seed prior to finishing up?
Studies have shown large differences between seeding rates of different varieties of alfalfa when seeded through the same seeder. Coated seed flows faster than uncoated seeds. If a farmer thought he was seeding 15 lb/acre but was actually seeding 20 lb/acre, the additional cost per acre for seed would be substantial.
Seeder calibration is an important consideration even when alfalfa varieties are changed. This can be done quickly and easily by driving the seeder over a tarp spread on the ground and counting the seeds dropped in several square foot areas on the tarp. Seeders that drop between 75 and 90 uncoated seeds per square foot are planting at recommended rates.