Evaluation and Modeling of the Impact of Environmentally Friendly
13
almost unaffected. In the loam, the leaching losses are small, as expected, while
the storage of N03'-N in the root zone significantly increases with an increase in
the rate ofN-release. This emphasizes the potential for postharvest N losses to the
environment, that are expected to increase as the release becomes faster. The loam
reduces the rate of N leaching as compared to the sandy loam, particularly under
band application, where an additional reduction of ammonium nitrification, due to
the higher concentration, occurs. In the heavier soil (loam) N uptake is less
affected by the rate of N-release since the N supply was about twice that of plant
need and the movement of the nitrogen forms is slower. These observations are
typical of many field experiments with EFFPs in which only the yield (i.e., N
uptake) serves as the criterion for evaluating the effectiveness of the fertilizers
(Shaviv, 2000). The environmental impact of using an EFFP is possibly
underestimated or even ignored if no effort is devoted to monitor changes of
concentrations ofN forms in soil profile and/or drainage.
Results show that the rate of supplying available N from a fertilized band to its
surrounding soil can be controlled by an appropriate combination of N-release
from a CRN and soil-inhibition capacity. The best agronomic and environmental
results are expected with the combination of banding and application ofCRN.
4 Summary and Conclusions
The influences of various environmentally friendly fertilization practices, EFFPs,
on N leaching and loss of gaseous N were studied experimentally in laboratory
and lysimeter experiments and analyzed via an N dynamics model. Emphasis was
on quantifying processes that may significantly affect the fate of nitrogen in soil
such as: nitrification inhibition due to local increases in ammonium concentration,
due to pH changes induced by ammonium oxidation, and due to the use of NIs.
Special attention was given to the impact of controlled-release of nitrogen. The N
dynamics model can be used for evaluating the agronomic (N uptake) and
environmental (nitrate leaching or gaseous emission) benefits expected from
applying EFFPs. The main points emphasized by the analysis done with the N
dynamics model are:
1. Fertilizer banding offers a reduction in the rate of nitrification and improved
conditions for nutrient uptake comparison to broadcasting. N losses are
reduced and the uptake of N is increased. Reliable knowledge regarding the
effects of nitrification inhibition due to high ammonium concentration and data
regarding ammonium lability in different soils is very important for such
simulations.
2. Increasing nitrification inhibition by adding nitrification inhibitors provides
another effective way of controlling N leaching when ammonium-N fertilizers
are applied. This option is more reliable (provides better control) than the
effect of high ammonium concentration, but it is associated with additional
costs. Combination of both NIs and high local ammonium concentration
further improves the control over N loss.
13
almost unaffected. In the loam, the leaching losses are small, as expected, while
the storage of N03'-N in the root zone significantly increases with an increase in
the rate ofN-release. This emphasizes the potential for postharvest N losses to the
environment, that are expected to increase as the release becomes faster. The loam
reduces the rate of N leaching as compared to the sandy loam, particularly under
band application, where an additional reduction of ammonium nitrification, due to
the higher concentration, occurs. In the heavier soil (loam) N uptake is less
affected by the rate of N-release since the N supply was about twice that of plant
need and the movement of the nitrogen forms is slower. These observations are
typical of many field experiments with EFFPs in which only the yield (i.e., N
uptake) serves as the criterion for evaluating the effectiveness of the fertilizers
(Shaviv, 2000). The environmental impact of using an EFFP is possibly
underestimated or even ignored if no effort is devoted to monitor changes of
concentrations ofN forms in soil profile and/or drainage.
Results show that the rate of supplying available N from a fertilized band to its
surrounding soil can be controlled by an appropriate combination of N-release
from a CRN and soil-inhibition capacity. The best agronomic and environmental
results are expected with the combination of banding and application ofCRN.
4 Summary and Conclusions
The influences of various environmentally friendly fertilization practices, EFFPs,
on N leaching and loss of gaseous N were studied experimentally in laboratory
and lysimeter experiments and analyzed via an N dynamics model. Emphasis was
on quantifying processes that may significantly affect the fate of nitrogen in soil
such as: nitrification inhibition due to local increases in ammonium concentration,
due to pH changes induced by ammonium oxidation, and due to the use of NIs.
Special attention was given to the impact of controlled-release of nitrogen. The N
dynamics model can be used for evaluating the agronomic (N uptake) and
environmental (nitrate leaching or gaseous emission) benefits expected from
applying EFFPs. The main points emphasized by the analysis done with the N
dynamics model are:
1. Fertilizer banding offers a reduction in the rate of nitrification and improved
conditions for nutrient uptake comparison to broadcasting. N losses are
reduced and the uptake of N is increased. Reliable knowledge regarding the
effects of nitrification inhibition due to high ammonium concentration and data
regarding ammonium lability in different soils is very important for such
simulations.
2. Increasing nitrification inhibition by adding nitrification inhibitors provides
another effective way of controlling N leaching when ammonium-N fertilizers
are applied. This option is more reliable (provides better control) than the
effect of high ammonium concentration, but it is associated with additional
costs. Combination of both NIs and high local ammonium concentration
further improves the control over N loss.