Incorporation of fertilizer after application reduces export by runoff.
The type of crop (non-row versus row crops) also influences nutrient loss to runoff
(row crops substantially higher).
Excessive or insufficient fertilization can increase nutrient losses to runoff
From the standpoint of
nuttiest load reduction, nutrient management is a
highly cost-effective practice. A primary reason for its effectiveness is that nutrient
management prevents the introduction of excess nutrients into the system. Most
other in-field practices depend on re-routing the excess nutrients through the soil to
achieve only partially effective adsorption or transformation. It should be noted,
however, that nutrient management is most effective in concert with practices that
increase infiltration. This allows more of the applied fertilizer to reach the root zone
for plant uptake (R. Hansard, 1994). Compared to structural practices alone, nutrient
management is also relatively inexpensive to implement. The primary expenses are
for soil tests and the development of a nutrient management plan. Camacho's
(1992) analysis of Chesapeake Bay Watershed Model results presents nutrient
management as the most cost-effective practice in use.
In an analysis of the literature on nutrient management, Casman (1990) concluded
that the efficiency of nutrient management depends primarily on the pre-BMP degree
of over-fertilization. This efficiency is roughly equal to the percent fertilizer reduction
recommended by the nutrient management plan. Consequently, the load reduction
associated with nutrient management will be highly site-specific, depending on the
individual farmers fertilization practices. See Chapter 4 for further discussion of
Nutrient management is not a formally cost-shared practice in North Carolina.
Farmers who use nutrient management in the basin do so on their own, or with
advice from the NCSU Cooperative Extension Service or private contractors. The
Soil Conservation Service also assists in nutrient management for organic sources
via the planning and writing of animal waste management plans. Since cost-sharing
nutrient management could be one of the most cost-effective means for reducing
nutrient loads in the basin, we are presenting cost-effectiveness values for
this practice. The best available effectiveness information is again from the
Chesapeake Bay Watershed
results. As we did for conservation
have taken the results of the model runs for the portion of the Chesapeake basin in
ecoregions 63 and 65. Because cost data are not available, we have used cost data
from the Chesapeake basin.
Camacho (1992) reports
as a typical cost for nutrient management plan development.
The resulting cost-effectiveness values for nutrient management on
summarized in Figure 2-6.