What is in this article?:
• For Kirk Brock and Myron Johnson, the search for an edge in making a living on the farm means thinking beyond the afternoon weather and putting confidence in science.
ALABAMA GROWER Myron Johnson talking with Wendy-Lin Bartels, an anthropologist with the Southeast Climate Consortium.
When to kill your cover crop
Rather than a neat square parcel with a house in the middle, Johnson’s farm is actually a collection of nearly 1,000 acres of fields spread out over 10 miles in a loosely strung pearl necklace.
From the center of operations, you get a sense of the never-ending stream of decisions that need to be made at different timescales.
There are herbicides that need to be applied at specific times, an army of tractors that need servicing at regular intervals, workers who have different hours of availability, a dog that needs to be fed, cows that need to be shuttled to open pasture, and oh, the cover crop and cash crop seeds that need to be planted.
On his Florida farm, Brock deals with a similar, sprawling layout. When I first walked up to his shop in February he was tweaking the engine of a dirt bike. That’s because his fields, which also total roughly 1,000 acres, are sometimes more easily traversed through right-of-ways and back roads more friendly to dirt bikes than trucks.
“We know the importance of getting the cover crop planted in a timely fashion,” Brock said. If you don’t put that effort in, “you won’t get the growth, and then the winter weeds will get started and have a foothold and limit how your cover crop will grow.”
From a climate perspective, what’s perhaps even more important to both men is when to transition from growing cover crops to killing them and planting cash crops.
There’s a delicate balance between having a hearty enough cover to protect the cash crops and not letting the cover crop grow so long it starts to suck up moisture and nutrients that the cash crop might need down the road.
With that timing so important, Johnson has turned to using the seasonal forecast based on El Niño, La Niña, and other factors.
Birdsong outlined exactly how that played out on Johnson’s farm last spring, when the forecast from the fall and winter of 2010 indicated that a La Niña event in the Pacific had increased the odds for a dry spring in 2011.
The spring 2011 precipitation outlook favored well below normal precipitation in the Southeast, a frequent outcome when La Niña events cool the eastern tropical Pacific.
“He put in a lot of effort to put the (cash) crop in early,” Birdsong explained.
“He sprayed Roundup on his cover crops to go ahead and kill them. If he kills it earlier, then it stops that plant from taking in more moisture and if he catches a rain or two, then with the cover on the ground, it’s insulating the ground to a certain extent to try and help cut down the amount of evaporation and store up some of the moisture.”
Johnson moved his planting schedule up to right after a March rainfall, when soil moisture was at its maximum, and squeezed the planting of his cash crops, which could take 10 days of work, into four or five, even as other farmers waited for another rain event, which historically happens at that time. Unfortunately for those who waited, “it didn’t happen until a month later,” Birdsong said.
“As it turned out, that gap in time of planting, the way the crop season turned out, meant the difference between making really good yields and mediocre to poorer yields,” Birdsong concluded. Johnson concurs. “Having the cover down and not losing those early runoff rains was a big thing for us,” he said.
When the row crop working group met in August 2010, the farmers were eager as always to hear from David Zierden, the Florida State Climatologist, or as the farmers affectionately know him, "the climate guy."
He helped start the working group and has a close relationship with a number of the Extension agents, particularly William Birdsong. "It started when I presented at his annual cotton expo about 12 years ago," Zierden recalled during a phone interview. "Now we're in constant contact during critical times during the growing season."
Zierden also brings his expertise directly to the farmers. He presents the forecast for the coming season and what it might mean for planting and other farming decisions at each row crop meeting.
He also takes the time to assess the previous seasonal forecast he shared with them so they can discuss what did or didn't happen.
Through these efforts, Zierden is cultivating relationships with growers, which require a lot of trust as well as an understanding of the limitations of the forecast he shares.
"We try to train farmers that these forecasts are probabilistic. It's a shift (in the odds) they need to be aware of," Zierden explained, rather than a guarantee that conditions will be warm or cold, hot or dry.
"Most of our seasonal forecasting is based on the El Niño and La Niña cycle," Zierden explained.