Ultra-early planting can work but there are risks
How early can soybeans be planted and have a yield advantage? Even with a yield advantage there is quite a bit of risk, or so it seems, to planting soybeans early. However, with new technologies on the market by way of seed treatments and varieties built to tolerate earlier planting, the risk of planting soybeans early is getting smaller every year. I began planting soybeans in March, and this time I could harvest them and get yield results. But let’s not start at the end with the results but rather how we got there, to better understand the yield numbers.
This soybean planting date study, “ultra” early vs. early, started on March 22. The plot was designed in a randomized block, not strips, to avoid bias and null out any environmental effects. At time of planting the soil temp was around 46° F. About 48 hours after planting we saw the soybeans had swelled up and the radical on the soybean plant had initiated growth. I checked the seeds again on April 3, 9 days after planting, and observed good development of the hypocotyl, which had begun to elongate. Around April 10th and 11th, 21 days after planting, emergence started. The initial stand count of the soybeans was around 130,000, from planting populations at 140,000.
The next round of planting began on April 15, which had the same planting population of 140,000. Emergence started between the April 23rd and 24th timeframe with emergence of 131,000 plants per acre. During the last week of April, the weather turned cold and wet, perfect environment for diseases to infect young soybean seedlings. After the weather started to dry and warm up, I did another population count at the results were painful. The March planted beans lost 30,000 plants per acre and were reduced to 100,000-110,000. However, the April beans fared much better with no noticeable seedling loss.
Now, you might be asking yourself why? When the late April rains started the seed treatment effect had probably dissipated on the March planted soybeans and they were essential “naked” compared to the April soybeans, which still had the positive effect from the seed treatment. During this time, I recognized lesions on the “necks” of the soybean seedlings which means a disease had infected the soybean plant. Luckily the population of the March soybeans did not fall below 100,000 plants per acre.
As the year progressed into late May and early June the soybean plants moved to the R1 growth stage. On June 1st, 50 percent of the beans planted in March were in the R1 stage for the 3.6 maturity ground and June 2nd for the 3.9 maturity group. The April soybeans reached the R1 stage on June 6th for the 3.6 maturity and June 8th for the 3.9 maturity group.
As we progressed into mid-August the soybeans planted in March begin to show signs of Sudden Death Syndrome (SDS). We could see the SDS-infected blocks in the aerial-image. The most severely infected blocks were the 3.6 maturity group planted in March, while there was little-to-no SDS infection on the 3.9 group. In addition to this, the April planted soybeans didn’t show any symptoms of SDS, neither the 3.6 or 3.9 groups.
Did the SDS damage translate into yield loss on the 3.6 group? When looking at the results, we noticed the SDS damage did cause a yield loss for the 3.6 group. The April 3.6 group out-yielded the March soybeans by 2.26 bushels. However, once we moved into the 3.9 group that was unaffected by SDS, we measured a 4.09-bushel advantage.
Overall, the March planted soybeans provided an additional 0.91 bushels/acre, a positive return. I will continue this study in future years to fully understand the impact of soybeans planted ultra-early.
As the harvest season starts to close around Illinois, it has been a pleasure serving as a CCA Soy Envoy for Southeastern Illinois in 2017. A special thanks to Dan Davidson, the Illinois CCA board and the Illinois Soybean Association for the opportunity.