To the question of whether or not you need tillage in Coastal Plain wheat production, the short answer is “yes.”
“Whenever we’re talking about Coastal Plain soils, they’re very prone to compaction. You need to eliminate that hardpan, and wheat definitely will respond to that,” says Kim Balkcom, USDA-ARS research agronomist.
The bigger question, says Balkcom, is what type of tillage to use on Coastal Plain soils. “Traditionally, we’ve used a disking operation and buried the residue and then come in with a chisel-plow operation to break up that hardpan. In our tests, we used a KMC subsoiler-leveler. It basically minimizes above-ground disruption, gets rid of the hardpan, and still maintains the beneficial residue on the soil surface. Compared to conventional tillage, we saw no difference if not a slight increase for our non-inversion type tillage. There was no issue with residue interference,” he says.
Increased no-till or reduced tillage practices among Alabama farmers prompted Balkcom, Auburn University Extension agronomist Charlie Burmester and other researchers to examine more closely how the trend might impact nitrogen fertilizer rates and timings in wheat production.
Balkcom discussed the research during the recent Central Alabama Wheat Expo held in Montgomery, Ala., focusing primarily on Coastal Plain production.
Alabama wheat farmers, he says, are changing management practices to maximize yields and reduce trips across their fields. Some recent changes include using higher nitrogen fertilizer and wheat seeding rates, in addition to planting wheat in no-till or reduced tillage systems.
Non-inversion tillage has been widely adopted in summer row crops, particularly cotton on Alabama’s Coastal Plain soils, while conservation tillage at planting has become a primary method on silt loam soils in the Limestone Valley, according to the researchers.
However, says Balkcom, there are concerns that tillage systems that maintain surface residue will slow vegetative growth and reduce tillering in wheat.
For their research, Balkcom and his colleagues used four locations across Alabama during the 2008, 2009 and 2010 wheat-growing seasons resulting in eight site-year comparisons. These locations were at the Tennessee Valley Research and Extension Center in north Alabama, the E.V. Smith Research Center in central Alabama, the Wiregrass Research and Extension Center in southeast Alabama and the Gulf Coast Research and Extension Center in southwest Alabama. The Tennessee Valley location represented Limestone Valley soils while the other three locations represented Coastal Plain soils.
Each wheat location in the study followed cotton and consisted of a split plot design with tillage as the main block and all nitrogen fertilizer treatments as subplots with each treatment replicated four times.
At Tennessee Valley, tillage variables included fall chisel plowing versus no-tillage before planting. At all other locations, surface tillage consisting of disking twice, chisel plowing and field cultivation were compared to a KMC Gen II subsoiler-leveler. The subsoiler-leveler operation was performed immediately after planting wheat to avoid tractor wheel ruts within the small plots.
Although cotton, a low-residue producing crop, was the previous crop across all locations, the data from Balkcom’s research indicate that maintaining surface residue did not hinder early season wheat development across the Limestone Valley soil, and it can enhance its development across Coastal Plain soils.
A balance must be obtained between fall-applied nitrogen and wheat development, he says. High fall-applied nitrogen rates could promote excessive vegetative development that can result in wheat being more susceptible to early freeze damage.
No differences were observed between wheat yields for conventional and non-inversion tillage systems at six of the eight site-year locations in Alabama. For the remaining two site-years, non-inversion tillage wheat yields were increased 33 percent and 64 percent compared to conventional tillage. These results indicate that concerns about slow wheat development associated with surface residue and subsequently cooler soils are not warranted in Alabama with cotton as the preceding crop, according to the research.
Some general conclusions from the research include that non-inversion tillage on CoastalPlain soils and no-till on Limestone Valley soils produced comparable or superior wheat yields across Alabama compared to conventional tillage. Also, fall-applied nitrogen was not necessary to optimize yields on Limestone Valley soils, but it was necessary for Coastal Plain soils. The nitrogen application window was wider for Limestone Valley soils, while Coastal Plain soils required all nitrogen applied by GS 25.
As far as phosphorus and potassium requirements on wheat, the easiest thing to do is to take a soil sample prior to planting your wheat crop, advises Balkcom. “Generally, wheat is sensitive to low-phosphorus fertility. But we’re usually not going to have low phosphorus levels. In any case, it’s an easy thing to correct. Wheat isn’t nearly as sensitive to potassium, but you will suffer some yield loss if you ignore your potassium requirements.”
Returning to nitrogen fertilizer, Balkcom says if you’re planting into sandy loam soils, be aware that they’re prone to leaching. “We applied nitrogen in the fall, and we applied only 20 pounds. In hindsight, I wish we had increased that just a little bit. We saw a big response in tillering from nitrogen in the fall.
“In our experiments, we were following cotton. If we we’re following corn, I’d almost say for sure to put out additional nitrogen because of the heavy residue. You don’t want to go too far on fall-applied nitrogen because if you have disease problems, you could be subject to some flush growth, and you could open yourself for winter kill.