Scientists in the College
of Agriculture and Life Sciences have been working to help agricultural
producers meet a revised federal nutrient management standard that requires
an assessment of phosphorus losses from farmland.
College researchers have
developed and tested the phosphorus loss assessment tool (PLAT). The
PLAT is an index that helps researchers determine total phosphorus losses
more accurately by accounting separately for different loss sources
and other factors. It measures the loss due to such considerations as
the chemicals binding to sediment, soil runoff, leaching and applications
Why the concern about phosphorus?
Farmers apply fertilizers containing essential nutrients such as phosphorus,
nitrogen and potassium to increase crop yields. Although the nutrients
are necessary, in excess, they overstimulate organisms in lakes and
streams, reducing water quality.
Current regulations base
the amount of nutrients producers can apply to a field on a crops
nitrogen needs, said Steven Hodges, former Soil Science Department extension
leader. But organic nitrogen sources also contain significant phosphorus.
Plants require much less phosphorus than nitrogen, so phosphorus can
accumulate in field soils. Over time, soil phosphorus builds to
very high levels, eventually moving from fields into surface and groundwater,
The revised U.S.
Department of Agricultures Natural Resources Conservation Service
(NRCS) phosphorus regulations could seriously impact producers, he said.
The regulations, effective
since April in North Carolina, could mean that some agricultural operations
that produce animal wastes might need to increase their land base.
Heres why: Under the
regulations, a fields assessed phosphorus loss potential
low, medium, high or very high determines if its nutrient management
plan can be based on the crops nitrogen needs. If the field shows
high phosphorus loss potential, it cant receive more phosphorus
than is removed in the harvested crop. If the assessment is very high,
only pre-plant phosphorus is allowed. And some land may not be allowed
to receive any phosphorus at all, so no manure would be allowed.
The critical issue
for animal producers is that they may have to expand acreage to handle
the manure they produce, Hodges said.
Producers dont have
to submit new nutrient management plans immediately, but phosphorus-loss-potential
assessments are mandated for any new site within nutrient-sensitive
watersheds that receive organic byproducts: manure or any nutrient source,
including fertilizers. Assessments also will be required when current
animal waste-management permits are reissued, if a waste-management
plan changes, or if a producer receives new state cost-share funds.
We have approximately
5,000 existing nutrient management plans in North Carolina based on
the previous nitrogen-based standard, he said. Since North
Carolina regulations simply adopt the latest NRCS standard rather than
writing our own, we needed to ensure that we had a science-based assessment
The PLAT was developed to
help remove guesswork from the planning process. The tool also includes
input about waste application and accounts for good crop management
by considering stream buffer lengths and widths, water control structure
use and pond and sediment basin use.
Before implementing the
PLAT and making it part of the North Carolina standards, researchers
rigorously tested its effects on producers.
Deanna Osmond, N.C.
Cooperative Extension soil science specialist and PLAT development
committee member, coordinated a study that randomly sampled about 1,400
farm fields across the state to run through the PLAT.
Hodges, We want regulators and the farm community to understand
the potential economic and environmental impact of this regulation.