Two aspects of stand establishment often discussed by agronomists are emergence and seed spacing. “Picket fence” spacing in corn helps plants grow efficiently and minimizes competition between them. Uniform spacing is an important part of stand establishment. More importantly, however, is uniform emergence. Plants that are just 1 leaf collar behind (due to uneven emergence) significantly reduce yield. According to Paul Jasa, University of Nebraska Extension ag engineer, “When a plant develops ahead of its neighbor, it hurts yield dramatically. It’s going to vary somewhat from year to year, but a plant lagging behind those around it becomes a weed.” To achieve uniform emergence, consistent planting depth is critical.
Field conditions, gauge wheel settings, unit down pressure, and planter speed all affect seeding depth. Set planter depth and check it regularly. A planter may have enough weight to apply the proper down force when full, but what about when it’s almost empty? If it is a model with center fill hoppers, is there enough weight on the ends? Additional weight may need to be added. Keep in mind, too much down pressure and planting in “marginal” or wet conditions can result in sidewall compaction of the seed trench, which will hinder root development and negatively impact yield.
Ground speed can greatly impact planter performance. Planting too fast may cause units to bounce, resulting in uneven seeding depth. Planter units and seed tubes are designed for accuracy at certain speeds. For example, if a planter is designed to drop seed correctly at 5 mph, planting at 6 mph will reduce the accuracy of seed spacing and can result in seed bounce, as well as seed placement on the side of seed trench instead of at the bottom. Following the equipment manufacturer’s recommendations and planting at the appropriate speed will improve the accuracy of plant spacing and depth.
Yields can be severely affected by late emerging plants. In a publication called: Uneven emergence in corn, The University of Wisconsin has documented as much as a 9% decrease in yield when 25% of corn plants were delayed a week and a half in emerging. Because emergence is so critical to yield, it is important that corn growers set up, adjust, and operate their planters to ensure uniform seed placement and even emergence this spring.