Nutrient management on organic farms still highly variable

WYE MILLS, Md. — Each participant received a small remote control.
Jenny Rhodes, ag and natural resources Extension educator for the University of Maryland Extension, was able to interactively survey the room about the day’s program.
With just a click of a button, audience members weighed in on the Queen Anne’s County seventh annual Organic Grain, Forage and Vegetable Production Meeting’s key issues.
More than 50 percent of the group wanted to increase on-farm research.
Dr. Michel Cavigelli, soil scientist for the USDA Beltsville, and Dr. Steven Mirsky, research ecologist, perform on-farm research with the assistance of a National Institute of Food and Agriculture grant.
“Little is known about best management practices for nutrient management of organic farms,” said Cavigelli.
Cavigelli said organic farmers practice good principles but there is not much quantitative data to fit the conventional models.
“We’re getting data through organic farmers like Luke Howard (in Millington, Md.) and others,” he said. “And creating research programs that can work on their farms.”
Cavigelli said the research looks at nitrogen levels in soil, produced by legume planting, and added by manure applications.
He said after one year, data varies greatly due to several factors.
“It all depends,” Cavigelli said.
Soil nitrogen is difficult to predict because it changes quickly. Legumes’ nitrogen levels depend on the harvest date and manure application levels depend on the nutrient content, he said.
Mirsky said the farms included in the research all had issues with phosphorus in the soil due to prior application of poultry litter.
Cavigelli and Mirsky have research plots on Bill Mason’s Heritage Farm in Ruthsburg, Md., Aaron Cooper’s Cut Fresh Organics Farm in Eden, Md., and Ed and Marian Fry’s Fair Hill Farm in Chestertown, Md.
The Beltsville site was designed as a control group. While each farm is different and has different needs, all used cover crops and poultry litter.
Mirsky said poultry litter application was applied to some of the research plots in pre-plant, side dress and some without poultry litter.
Cover crops included hairy vetch, Austrian winter peas, and crimson clover. One rotation remained fallow in winter weeds, said Mirsky.
The study also used Fair Hill Farm’s perennial cropping system.
The research tested alfalfa when killed, plowed under, and harvested for forage.
After the alfalfa, rye was planted in late summer, said Mirsky.
“This is just our first year’s findings,” he said. “It was a dry year so we only saw a moderate increase in yield with the cover crops.”
Mirsky said there was no evidence of side dress application advantage yet.
Cavigelli, who also farms organically, said that more research is needed so organic plans better correspond with current nutrient management plans and the incentives for cover crops.