John Baker, CEO of Cross Slot No-Tillage Systems, shared his thoughts on a recent article we published from Kansas State University Extension, “Most Likely Causes of Poor Wheat Emergence.”
The explanation regarding the causes of poor emergence and stand establishment is simply incomplete. The most serious cause is poor imbibition by seeds from the soil micro-environment that is created around them by the openers on the drill that is used.
Regarding the problems caused by high soil temperatures, all of those things are true but their influence in fact is more minimal. For example, the photos suggest to me that the main cause of seedling emergence impairment in that instance was most likely a combination of low vigor, depth of seeding and soil environment.
The tell-tale sign is twisting of the coleoptile. That only happens if the seed vigor (as determined by an “accelerated aging” test conducted by a seed testing authority) has shown the seed had to have had less than 90% vigor. It seems that no such test was conducted on this sample of seeds. What happens is that low vigor seeds (and we have seen 50-60% vigor in seeds that had given 90%-plus final germination counts) are unable to handle the added stress of deep planting, whereas high vigor seeds may well have done so.
But even then if the deep-planted seeds had been encased in a cocoon of 90-100% relative humidity in the soil pore spaces from the time they were buried, the low vigor seeds may well have emerged and then performed poorly as a crop. In fact, if the seed and seedling of either plant had been placed in a soil environment that maintained the pore space humidity at 90-100% relative humidity, the seeds would have happily emerged unscathed.
How do you get the pore space to remain at 90-100% relative humidity? By avoiding all soil inversion, even with the slot, and covering the slot with a residue-mulch as the seed is sown. No tined opener does that and most disc openers do not it either. But there are specialized, low-disturbance no-tillage disc openers that do it at up to 10 mph. As a result, crops sown by these openers seldom ever have a germination or establishment failure.
Suffice to say this is one of the main things that distinguishes low-disturbance no-tillage from strip-tillage. Even the photos suggest that the seeds were sown into an artificially prepared soil medium rather than in a truly untilled, residue-covered soil medium — and believe me, there is a world of difference.
Finally, the point about wheat possibly not emerging if it’s planted deeper than 2.5 inches is rubbish. We have seen canola emerge happily from these depths and wheat emerge from a depth of up to 4 inches. It is more about the humidity of the soil environment than the seeding depth.