With cotton yields having plateaued in recent years, Bill Pettigrew says he wondered if moving planting dates back would give the crop a boost. This approach was viewed as a bit odd by many farmers, says Pettigrew, because it's commonly believed that optimum planting date questions were answered 30 years ago.
Pettigrew, a USDA/ARS crop physiologist stationed in Stoneville, Miss., came to planting early cotton in a roundabout way. “Some research at our lab showed that lint yields in the Mid-South are limited by the amount of sunlight the crop receives during the growing season. We've got an ongoing research project that's looking at the photosynthesis of the plants.
“We're wanting to identify some lines that make better use of photosynthesis than others. Frankly, that's a long-term project and it's high risk. At the end of the day, we may end up with nothing useful,” says Pettigrew, who spoke at the Milan, Tenn., No-Till Field Day.
“We decided we would come up with a project that would yield some information in the short-term.”
One of the things even early man knew is that the longest day of the year is the Summer Solstice — the first day of summer — which occurs about June 21 every year. Because of cotton plant physiology, it would make sense to have the peak flowering period for a cotton crop land on that day. However, the peak flowering period in Mississippi occurs in mid-July. Pettigrew and colleagues wanted to shift that period to coincide with the Summer Solstice.
The initial way he tried to do this was to push back planting dates as early as possible and still have a viable stand. Five years ago, Pettigrew seeded some small plots and started collecting data.
“We went in and over-seeded the plots and came back and thinned the plants back to a desired population — typically three plants per foot. That way we were taking stand establishment out of the equation. We wanted to be able to see if we could get the stand, then what was the yield potential? What's the yield compared to a typical planting date?”
For the experiment, Pettigrew looked at eight varieties. One of them was Sure-Grow 125. Another was MD-51 — a little known, high strength variety released about seven years ago. The other six varieties were chosen because Pettigrew thought they might offer a degree of cold tolerance.
Over the life of the experiment, results have tended to see-saw.
“In 1996, our April 1 planting compared to our May 1 planting shows that our peak blooming period shifted 10 to 14 days. We didn't quite accomplish our goal of hitting the Summer Solstice, which is about the 172nd day of the year.”
In 1997, the systems were almost on top of each other. About two weeks after the early plants emerged, a rather severe cold snap hit. Temperatures dropped to around 36 degrees and the cotton browned up and stunted. That meant the plants didn't really start growing well until the May 1 planting had emerged.
“In 1998, there was not much of a peak shift. But we did get many more flowers produced early.”
However, in 1999, a considerable shift in the blooming period meant the experiment had new legs.
“In 2000, the two systems peaked about the same time. The early planting did produce more flowers early.”
In 2001, planting was done on April 2. Pettigrew has photos showing the emerging, healthy plants on April 16. “We knew a weather system was moving in and bringing cold air about 39 degrees. It hit the next evening. Eight days later, the cotyledons were browned. The good news is the plants grew out of the browning.”
Bottom line? Looking at five years of data, Pettigrew's crop averaged about a 10 percent yield boost from planting April 1 vs. May 1.
Some of the benefits of planting early:
Potential increased yield. “That may not occur every year, but it's generally true.”
Input reduction. “By avoiding some of the late season stresses, you're able to reduce the need for inputs.”
More efficient use of labor. ‘You can't plant all your crop the same day, nor can you harvest it all the same day. So you can spread out labor a little more.”
Cold temperature stres