One crop production practice is used by all top-yielding producers and is the foundation of managing disease, weeds and insect problems, as well as fertility. What is the one practice important enough to have been mentioned in the Bible? Crop rotation.
“The winners of the Georgia Peanut Achievement Club’s top peanut yield awards have all had one thing in common – a long rotation,” says John Beasley, University of Georgia’s Extension peanut agronomist. “With very few exceptions, maybe one or two growers over 23 years, all winners have had a four-year rotation or longer.”
Beasley says that in more than 300 winners, he can only remember one or two situations where the winner had only a three-year rotation, which is the minimum rotation recommended by the University of Georgia.
“All other production practices had a lot of variability,” he says.
Foundation To Build From
The practice of good crop rotation has always been at the foundation of optimum disease management, affecting not only nematodes and soilborne diseases, such as white mold, Rhizoctonia limb rot and Cylindrocladium black rot, but leaf spot diseases as well, says UGA plant pathologists Bob Kemerait, Tim Brenneman and Albert Culbreath in the 2009 Peanut Disease Update.
“One of the greatest benefits of crop rotation is that it increases the effectiveness of all disease management programs. Effective crop rotation takes some of the ‘pressure off’ of a fungicide program to minimize the impact of disease.”
The researchers conclude that any fungicide program will be more effective where good crop rotation is practiced.
“In some situations, fields that are well rotated will require fewer, or at least less expensive, fungicide applications.”
Where To Go From Peanuts
While it may be easier to respond to crop prices when deciding what to plant in the coming year, making a long-term plan with good rotation in mind is a more sound option in the long run.
“It is important to know what crops are good candidates for rotation with peanut,” Beasley says.
For the most part, the best rotation options are the same throughout the peanut belt. See the box on page 15 for rotation options. However, there are regional differences based on different cropping schemes and shifting disease issues.
In South Carolina, Jay Chapin, Extension peanut specialist, says that rotation into non-legume crops such as cotton, corn or other grasses is essential to sustainable, long-term production. However, rotation with tobacco would likely increase white mold pressure.
“Cylindrocladium black rot is increasing in South Carolina, and rotation is the most important factor in suppressing this and other diseases,” Chapin says. “Soybeans should be avoided in a peanut rotation due to increased CBR and white mold problems.”
Crop Rotation Options:
Best Bets - Grass crops, such as corn, sorghum and bahiagrass, will help reduce the severity of white mold, leaf spot and other foliar diseases, CBR and diseases caused by Rhizoctonia solani. Corn and sorghum are hosts for peanut root-knot nematode, but are less effected and populations may be reduced.
Good Bets - Cotton should help reduce the severity of white mold, leaf spot diseases and CBR on future crops. Cotton is not a host for the peanut root-knot nematode. However, it is a host for Rhizoctonia solani, so diseases caused by this pathogen remain a concern, especially in conservation tillage where crop debris remains on the surface.
Worst Bets - Soybeans, other leguminous crops and many vegetable crops are not a preferred rotation crop with peanut. Although such rotations are likely to reduce the severity of leaf spot diseases, it may not reduce the severity of white mold, Rhizoctonia limb rot, peanut root-knot nematode or CBR.
Source: Georgia Cooperative Extension Service.
Big Part In Weed Control
Rotation plays a foundational role in weed control. Weeds that are difficult to control in peanuts may be more easily controlled in the rotation crop. Also, crop rotation allows for the rotation of herbicide modes-of-action, which reduces the risk of developing herbicide resistance.
“Rotation can play a big part in the control of glyphosate-resistant weeds as long as the grower is using other chemistries in a program,” says Eric Prostko, UGA Extension weed specialist.
For example, he says, it does no good to rotate from Roundup Ready corn to Roundup Ready soybean to Roundup Ready cotton.
“However, if you use residual herbicides such as atrazine (corn), Valor (peanut), Reflex (cotton) and Sencor (soybeans), then you can fight the weed battle and still use Roundup Ready crops.”
One of Prostko’s biggest concerns is the development of PPO resistance.
“Currently, we are being forced to use PPO herbicides that provide good pigweed control. However, these can be used in multiple crops, thus one could say we are overusing them.” For example, using Reflex in cotton and soybean, Valor in peanut and soybean and Cobra or Blazer in peanut and soybean.
“One of my mantras has been Valor for peanuts, Reflex for cotton, atrazine for corn and Sencor for soybeans with the hopes of preventing PPO resistance.”
Make A Written Record
David Jordan, North Carolina Extension agronomist, says, in developing rotations for 2010, producers should remember to look at specifics such as herbicide carryover and also to write down observations of this year’s weed management program to use in planning.
“Look carefully at what was going on in each field to make the best decisions for similar fields the following year or the same field years down the road.”