Profits come from balancing opportunity and risk. Despite onerous manure regulations, Kristin Whittington emphasizes opportunity first.
As the owner of Landmark Enterprises, Edinburgh, Ind., she advises livestock producers on manure management. She always starts with manure’s economic value, analyzing a sample’s nutrient content and pricing it against commercial fertilizer.
That’s just the base. She’s seen manure’s added benefits on her own farm with increased organic matter and micronutrients, and increased corn and soybean yields with fewer inputs. Most of her livestock clients have seen similar results. However, results vary from year to year and field to field.
It’s not easy to understand when manure works and why, not to mention how to get enough nutrients without over-applying. Whittington recommends tissue testing, plus comparing results and yields across multiple years on manured and commercial fertilizer-applied acres to learn manure’s value.
Tracking what was applied, how, where and with what results is key to understanding manure’s nutrient value, says Peter Kyverga, senior research associate, Iowa Soybean Association's On Farm Network.
While his research and farmer-related experiences support manure’s positive long-term effects on soil fertility and quality, it can be hard to quantify, Kyverga says.
Manure’s variability is the main challenge, he says, because it doesn't perform like a commercial N source. “You have ammonia and nitrate losses, application variability, weather’s impact and soil differences, including carbon:nitrogen ratios and complex microbial activity,” Kyverga says. Sources can vary due to different storage and rations, he adds.
He compares manure management to any risk-management exercise...plan, execute, evaluate and adjust. "Make the recommended application. Then look at aerial field images for variations and ask what happened," he advises. “Add the late-season cornstalk nitrate test, the pre-sidedress soil-nitrate test, data of yield response to various N treatments, consider rainfall, and puzzle out the whys. Review the data, look for the problem and try to solve it.”
Joshua Gaddy, agronomist, Murphy-Brown, Warsaw, N.C., is confident he’s solved several problems with manure-application variability. He is a member of a Murphy-Brown team charged with distributing swine-lagoon effluent across 8,500 acres on North Carolina’s coastal plain. The state has very strict regulations for the amount of N and P on particular soil types, while limiting application volume to any one field. If he loses fields to excess nutrient levels, lagoons can't be pumped, and hog production stops.
Their priority is to safely manage lagoons, yet be very cautious not to over- or under-apply, producing the best possible crop, Gaddy says. "If we under-apply, we don't produce a crop capable of removing the nutrients from previous years, and P levels rise."
He faces all the variability labels Kyverga describes and more. Adding a GreenSeeker crop-sensing system to his agronomic tools has helped. Based on a field’s crop variability, the GreenSeeker automatically adjusts supplemental N application at field edges that didn't get watered, as well as across fields where nutrient needs were not met for whatever reason. Combined with zoned application of the effluent, Gaddy can be sure field needs are getting met.
"It has really improved our crop yields,” Gaddy says.
In Ohio, Glen Arnold's job is to increase manure’s value. The Ohio Extension nutrient-management field specialist works closely with farmers to develop sidedressing equipment for swine and dairy effluent. He notes that crop producers tend to discount N’s value in fall- and spring-applied manure. Even P and K are usually discounted due to concerns over compaction and odor.
In-crop applications have the potential to capture N’s value, Arnold says. “Tissue testing in fields where we sidedressed with liquid manure showed similar N, P and K levels as commercial fertilizer applications, but plants were darker and had more zinc. Farmers pay good money for micronutrient packages, and it's all there with manure."