Published on Wednesday, November 07, 2018
Planting depth for row crops is a main topic of discussion in the agricultural community. Beck’s PFR team has heard your questions and in response, has put planting depth to yet another test. You may have seen our planting depth data over the last few years, but this year we added a second planting date into the mix. For this study, we planted corn in April and in May. In April, we tend to see cooler, wetter soils whereas in May we sometimes experience drier periods with less rainfall and warmer soil temperatures. Soil temperature and moisture have a great effect on how plants emerge. In this study, we looked to evaluate how much soil conditions can affect plant emergence, and how much yield potential we lose with late-emerging plants.
In April, soil temperatures typically range between 50 to 65°F depending on the region. With that said, planting depth must be considered when planting into cooler, wetter soil conditions. We need to ensure the seed is placed at the depth where soil temperature and moisture are relatively uniform. When those two factors are constant, we can expect to see more even emergence. However, uniformly poor conditions can also be a challenge. If we plant a field at 2 in. into soils at 55°F, the combination of cool soils and deep planting would likely lead to uneven emergence and possibly a lack of germination. Shallower planting depths could have a great effect on how evenly plants emerge in those earlier planting situations. On the flip side, planting in May can raise some questions about planting depth as well. Soil temperatures in May are quite a bit warmer than those in April, but soil moisture can be lacking. Water is the most limiting factor for plants to germinate so, in drier planting conditions, we need to plant the seed deep enough to ensure that soil moisture is consistent. If we normally plant at 1.5 in., then we may consider going to a 1.75 to 2 in. depth to achieve consistent soil moisture.
In 2018 at our Central Illinois PFR site, we experienced these same planting conditions for of our both planting dates. Coming into April, we saw a long period of cooler temperatures until the latter half of the month when we were able to get in and plant some of our plots. On April 26, our soils were at 62°F with relatively ample soil moisture. When it came time to plant our May plot, our soils were around 74°F and had received minimal rainfall but still had ample soil moisture. Throughout the 2018 growing season, this site experienced below average rainfall and once the plants started emerging, our team conducted 12-hour emergence counts. Twice a day, they would count the plants that had emerged over the prior 12 hours. Each 12-hour count represented an emergence event, which are illustrated in Figures 1 and 2 below.
Looking at Figure 1, you can see all the planting depths with their corresponding total plants emerged for the first planting date. Within each planting depth, you will see several different colors which represent each emergence event. Ideally, the bar would be all one color, with all plants emerging in one 12-hr period. The 1 in. depth clearly had the fewest emergence events compared to the control 1.5 in. depth which had the most. The 1 in. planting depth put the seed deep enough into the soil to achieve adequate seed-to-soil contact but still placing the seed close enough to the soil surface for even soil temperature. The 1 in. depth has the fewest total emerged plants out of all the treatments which could have been caused by many factors such as the soil type it was planted in to or the positioning of seed.
The May 11 planting date (Figure 2) experienced fewer emergence events overall and more consistent emergence across all planting depths. With warmer soil temperatures and ample soil moisture at planting, we achieved almost 100% emergence at each depth. Even though the 1 in. and 2 in. depth had more emergence events, they had the highest number of total emerged plants for the second planting date. While emergence does play a big factor in overall yield, it does not necessarily tell the entire story. One treatment could have fewer overall plants emerged and still yield equal to, if not higher than another treatment. Keep in mind, the data shown in figure 1 and 2 was only pulled from one location and one replication in the study.
Harvest started and ended earlier than normal this year in Central Illinois. Figure three depicts data from the first planting date in which the 1 in. depth won with almost a 3 Bu./A. yield. gain over the control. When we look back to Figure 1, the 1 in. depth had the fewest emergence events. In the second planting date, the 2 in. depth won with almost a 0.5 Bu./A. yield advantage over the control. It did not provide as much of a response over the control as the 1 in. depth did in the first planting date, but we still saw a yield response by simply changing depths in response to soil conditions.
This study isn’t designed to tell farmers how to plant, when to plant, or at what depth to plant. Rather, we are trying to provide some insight into how important adjusting your planting depth can be when it comes to emergence. Studies like this are great to consider because it does not cost you any money to implement this onto your farm. Implementing changes in planting depth in response to soil moisture and temperature will help you see better emergence on your farm overall. Pictures 1 and 2 below provide a visual representation of the difference between the two planting dates and the emergence events that took place.
Picture 1 (April 26 Planting Date)
Picture 2 (May 11 Planting Date)
We’ve covered how much planting depth and timing can influence emergence, but how much can late-emerged plants affect your overall yield potential? We performed 12-hour emergence counts and weighed the yield for each emergence event at all depths and both planting dates. Then, we compared every subsequent event to the first emergence event at that planting depth. This allowed us to calculate how much late-emerged plants cost us in overall yield potential. In Figure 4 we see that, on average across all depths, late-emerged plants cost us around 6.4 Bu./A. in yield. This shows us how important achieving uniform emergence is to reach your best yield.
This study has provided us with a large amount of data in just our first year of research. While we understand that once the seed is in the ground there are very few things you can do to improve overall emergence, we challenge you to think about emergence before you even start planting. It’s important to understand what factors (such as tillage, crop residue, environmental pressures, etc.) can affect plant emergence and how can we address these issues. And while we can’t address every factors all of the time, we can minimize the influence they have on emergence. When it comes time to plant, think about planting depth, soil temperature and soil moisture. Taking all of these factors into consideration will give your crop the best overall yield potential on your farm.
Author: Jim Schwartz
Categories: PFR, PFR Reports
Tags: corn, Agronomy, Corn Planting Date, PFR, PFR Report, research, corn planting depth
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