Agriculture Reference
In-Depth Information
It has previously been indicated that trade-offs exist between environ-
mental and economic benefi ts, because practices which reduced NO 3 - -N
losses caused lower economic returns [28]. Also, vegetable production
practices, which reduced NO 3 - -N leaching, did not always coincide with
those that generated optimal economic outcomes [29]. Although a prior
study on “fat oil grease” amendments did not specifi cally determine the
economic impact [16], the impact can be estimated based on the observed
effects on the following corn yield and N requirements. The reported mean
control plot yields [16] and the average Ontario prices in 1996 and 1997
for corn and urea [48] suggested that the use of “fat oil grease” reduced
the revenue by as much as $290 ha -1 and increased the input costs by about
$52 ha -1 . The reduced profi t margins of autumn applied OCA in corn was
similar to the present study in a broccoli-spring wheat rotation. Thus, best
management practices that have environmental benefi t may also have an
economic cost for growers.
3.4 CONCLUSIONS
Better N management practices are necessary after cole crop produc-
tion due to the high SMN concentration and the risk for N losses in
the post-harvest season. Although the OCA-straw demonstrated reduced
autumn SMN concentrations after the early-broccoli system, it is not rec-
ommended if spring wheat is the following crop due to yield reductions.
Also, the OCA-yard showed inconsistent potential for reduced autumn
soil N losses. However, the practice of OCA-oil is recommended due
to the reduced potential for autumn N losses via N immobilization af-
ter both early- and late-broccoli systems, without the subsequent spring
wheat yield being detrimentally affected. This field study was consistent
with previous incubation research, which found that OCA-oil demon-
strated the most promise for the potential reduction in soil N losses after
broccoli harvest [11]. Despite the environmental benefits of potentially
reduced N losses by OCA, economic costs were associated. Thus, grow-
ers must evaluate the environmental vs. economic benefits of OCA-oil
compared to the typical practice.
 
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