CHRISTIANA, Pa. — If Tim Fritz’s experiments are any indication, the next step in cover crop innovation could be tailoring cover mixes to the needs of the cash crop.
Fritz started down his current line of research a few years ago when he began working with a German company that was developing complex, cutting-edge strategies for cover cropping.
Because of the Chesapeake Bay cleanup, Fritz figures that the Mid-Atlantic is one of the most advanced places in the U.S. on cover crop thinking. But the Germans are well ahead even of Pennsylvania.
“There were some of these ideas that were kind of like ‘huh?’” Fritz said.
One of the most interesting propositions was that the cover crop could do more than stave off erosion and build some organic matter. It could actually get the soil into optimal condition for the following cash crop to succeed.
When used for this latter purpose, the planting is called a forecrop.
Fritz decided to try developing forecrops for tobacco — an important crop in southern Lancaster County — and for hemp, a newly available crop with little local research on it.
Having experimented since 2019 on his farm and with cooperating farmers, Fritz said he’s developing a sense for what forecrop mixes will work best.
One year Fritz and a farmer weighed the tobacco from the plots and found that forecrops could lead to yield variations as much as 19% below average or 10% above average.
This year’s plots aren’t replicated, so Fritz is planning to base his recommendations on visual observations rather than yield data.
Finding the Right Mix
Still, it appears that some forecrops led to better results than others did, and the mixes that worked for tobacco weren’t necessarily the ones that were best for hemp.
“It’s not down pat. We’re dialing it in, though,” Fritz said.
Fritz found that mixes with a lot of complementary species generally did best, though mixes don’t need to have every species imaginable.
“You want complex mixtures that are smart mixtures designed for your target crops,” he said.
Using principles from the Germans, Fritz designed mixes with species that would die off at different times and slowly feed the soil. A burndown herbicide that kills all of the plants at once can disrupt the food supply to soil microbes.
The mixes were planted Aug. 28 and Oct. 8, 2020, and March 22 this year. The hemp was planted and the Maryland 609 tobacco was transplanted later this spring.
One forecrop mix of about a dozen species was good enough that Fritz named it — Construct, suggesting that it builds the soil.
The tobacco following Construct was tall and fairly consistent throughout the plot. As with other complex forecrop mixes, Fritz said Construct should be planted light — maybe even lighter than his official recommendation for the mixture.
Going easy leaves space so that the less competitive species don’t get choked out by the more aggressive ones.
“It’s not like forages here, where we want to plant heavy,” Fritz said.
Another complex mix apparently gave the tobacco a boost because the mix contained a lot of legumes. But in most of the plots, Fritz kept the legumes to a minimum because tobacco growers told him those plants could lead to black shank.
Fritz’s pick for a spring-planted forecrop was Cosaque black oats, which are used for cover crops and forage rather than grain.
In the less successful plots, the tobacco stands were uneven or noticeably shorter than the plants in the other plots.
In general, Fritz said, small grains are undesirable forecrops for tobacco, while brassicas provide nice tilth.