What is in this article?:
- Oct. 8 freeze damages South Plainsâ€™ grain sorghum crop.
- Maturity is a key factor
- Warmer temperatures may help some recovery.
- If fields were still green and kernels were in the milk stage, there is little expectation of any sufficient grain development.
- Lubbock recorded the second earliest freeze on record.
This Oct. 10 picture shows grain sorghum heads at different stages that have been exposed to modest freeze injury. In this field, significant undamaged leaf area remains in the lower 2/3 of the canopy suggesting the conditions did not represent a hard freeze in spite of the appearance of the top leaves. Texas A&M AgriLife Extension Service agronomist Dr. Calvin Trostle said fields should be observed for the presence of stalks that are frozen above the canopy, which would indicate no further seed maturation.
Maturity is a key factor
Grain fill can continue after a light freeze if sufficient leaf area remains undamaged, the stalk is not frozen and temperatures warm up enough after the freeze to drive growth again as the plants attempt to recover from the cold shock, he said.
Temperatures in this region climbed back into the 70s and 80s, so there is a greater possibility that damaged sorghum may indeed have sufficient warmth left in the season to resume meaningful dry matter accumulation, Trostle said.
“If the freeze was light and there is still significant green foliage, then the grain sorghum should be able to take advantage of available heat units to continue maturation, albeit slow, especially when days reach highs of 75 degrees and nights stay at 50 degrees or higher.”
Trostle said it’s highly questionable if grain in the milk stage during the Oct. 8 freeze will develop well, even if the damage was moderate and warm temperatures returned.
“You can’t accurately gauge growth stage of development while driving past a field,” he said. “However, in my experience, when the first tint of color is visible across a field, then the hybrid is most likely at the beginning of soft dough. A general pronounced coloration across the field is often indication of hard dough.”
Trostle said among representative later-planted fields, he has seen about a 10-day difference in maturity.
“If heat is available, I believe we will get some further development in the soft dough grain moving on to early hard dough, provided freeze injury was moderate at worst,” he said.
He said fields that show evidence of moderate freeze injury, which were greater than 60 percent milk stage and largely green across the field, should not be expected to develop any meaningful grain yield from this immature grain.
“At this point, no milk stage grain will reach hard dough, even if weather is favorable,” Trostle said. “If the injury is moderate and the leaf sheaths are not damaged, expectations of grain development with reduced test weight are still only modest.”
Trostle said producers can find a more detailed breakdown of the situation at http://lubbock.tamu.edu under the title Freeze Assessment on Grain Sorghum – South Plains – Oct. 8, 2012.