Evaluation and Modeling of the Impact of Environmentally Friendly
9
of crop harvest (=residual N). Simulations were used to compare the practices of:
split application vs. one single basal application; band vs. broadcasting over the
whole field; easily dissolving fertilizer (EDF) vs. controlled-release nitrogen
(eRN) and the effect of reducing nitrification by nitrification inhibitors (NJs). In
all cases ammonium fertilizers were compared to nitrate fertilizers.
3.2 Effectiveness of EFFPs Under Broadcasting
3.2.1 Effect of Split Application
The well-known effect of split application of EDF was simulated for three
fertilization schemes of: one, two, and three fertilizer applications of either
ammonium or nitrate. Table 1 shows that more N is leached out of the root zone in
the case of one application than in the other two cases, whether an ammonium or a
nitrate fertilizer is applied. Yet, the difference in N leaching is much smaller when
applying ammonium than when applying nitrate. N leaching from the soil is also
determined by the rate of nitrate formation, which can be strongly affected by
nitrification inhibition. A somewhat stronger inhibition is expected with one
application of ammonium than with two or three applications due to the higher
ammonium concentration induced after fertilization. Thus, N losses due to
leaching may be reduced, to some extent, by the corresponding difference in
nitrification inhibition.
Table 1. Effect of number of applications (broadcast) on N loss and uptake in a sandy loam
No of splits/
N stor~fe
fertilizer
Leachn.
Volatil.
Uptake
(kg ha )
-I
(kgha,l)
(kg ha'l)
(kg ha )
N03'
NII4+
One/
70
27
124
42
50
(N1I4 +)
Two/
55
31
124
40
62
(N1I4 +)
Three/
52
28
125
42
66
(N1I4 +)
One/
244
1
55
5
3
(N03')
Two/
142
101
60
6
(N03')
Three/
137
123
40
7
(N03")
9
of crop harvest (=residual N). Simulations were used to compare the practices of:
split application vs. one single basal application; band vs. broadcasting over the
whole field; easily dissolving fertilizer (EDF) vs. controlled-release nitrogen
(eRN) and the effect of reducing nitrification by nitrification inhibitors (NJs). In
all cases ammonium fertilizers were compared to nitrate fertilizers.
3.2 Effectiveness of EFFPs Under Broadcasting
3.2.1 Effect of Split Application
The well-known effect of split application of EDF was simulated for three
fertilization schemes of: one, two, and three fertilizer applications of either
ammonium or nitrate. Table 1 shows that more N is leached out of the root zone in
the case of one application than in the other two cases, whether an ammonium or a
nitrate fertilizer is applied. Yet, the difference in N leaching is much smaller when
applying ammonium than when applying nitrate. N leaching from the soil is also
determined by the rate of nitrate formation, which can be strongly affected by
nitrification inhibition. A somewhat stronger inhibition is expected with one
application of ammonium than with two or three applications due to the higher
ammonium concentration induced after fertilization. Thus, N losses due to
leaching may be reduced, to some extent, by the corresponding difference in
nitrification inhibition.
Table 1. Effect of number of applications (broadcast) on N loss and uptake in a sandy loam
No of splits/
N stor~fe
fertilizer
Leachn.
Volatil.
Uptake
(kg ha )
-I
(kgha,l)
(kg ha'l)
(kg ha )
N03'
NII4+
One/
70
27
124
42
50
(N1I4 +)
Two/
55
31
124
40
62
(N1I4 +)
Three/
52
28
125
42
66
(N1I4 +)
One/
244
1
55
5
3
(N03')
Two/
142
101
60
6
(N03')
Three/
137
123
40
7
(N03")