10
A. Shaviv
3.2.2 Response of corn to N application rate
Since most of the simulations were performed with N levels double the potential
uptake by plants to evaluate realistic conditions, it was also important to evaluate
NUE and environmental impact under higher and lower levels of applied nitrogen.
This is demonstrated in Table 2 for two extreme cases: single application of eRN
(~+) as compared to a single application of EDF (N03-) in a sandy loam soil.
Table 2 shows that N leaching below the root zone is relatively small and only
slightly affected by the application level of N in eRN ~ +). With EDF (N03)
the losses of leached nitrate were extremely high, linearly increasing with N
application level. The maximum possible N uptake (about 125 kg N ha-!) is
reached with a eRN ~ 1 slightly exceeding 150 kg N ha-!. On the contrary,
with one application of EDF (N03-), N uptake is significantly smaller than the
crop's maximal N uptake, and even with 400 kg Nha-! the uptake is about half the
maximal uptake! This, again, stresses the well-recognized need to improve basal
(single) fertilizer application methods in order to achieve reasonable crop yields
and reduce environmental threats in soils having a high nitrogen leaching
potential.
Table 2. Effect of application rate ofEDF and eRN on N loss and uptake in a sandy loam
Applied
-I
N uptake (kg ha )
N leaching (kg ha- I )
N
eRN
EDF
eRN
EDF
-I
(kg ha )
(NR!+)
(N03)
(NR!+)
(N03-)
100
93
35
46
119
150
115
42
46
161
200
123
50
47
201
250
125
55
48
244
300
129
61
49
286
400
129
67
54
374
3.3 Effect of Fertilizer Broadcasting and Banding on N Leaching
and N Uptake
Two types of soil (sandy loam and loam) and two types of fertilizer (ammoniumNand nitrate-N) were examined (Table 3). Band application of ammonium-N to a
sandy loam leads to significantly smaller N leaching as compared to broadcasting
due to the effect of nitrification inhibition caused by banding. Band application of
nitrate fertilizers in the sandy loam slightly reduces N leaching, and increases N
uptake in comparison to broadcasting. Banding also significantly reduces the
volatilization losses of ammonia due to a smaller area of contact with air and to
the band placement at a depth of 5 cm below the soil surface. The amount of N
A. Shaviv
3.2.2 Response of corn to N application rate
Since most of the simulations were performed with N levels double the potential
uptake by plants to evaluate realistic conditions, it was also important to evaluate
NUE and environmental impact under higher and lower levels of applied nitrogen.
This is demonstrated in Table 2 for two extreme cases: single application of eRN
(~+) as compared to a single application of EDF (N03-) in a sandy loam soil.
Table 2 shows that N leaching below the root zone is relatively small and only
slightly affected by the application level of N in eRN ~ +). With EDF (N03)
the losses of leached nitrate were extremely high, linearly increasing with N
application level. The maximum possible N uptake (about 125 kg N ha-!) is
reached with a eRN ~ 1 slightly exceeding 150 kg N ha-!. On the contrary,
with one application of EDF (N03-), N uptake is significantly smaller than the
crop's maximal N uptake, and even with 400 kg Nha-! the uptake is about half the
maximal uptake! This, again, stresses the well-recognized need to improve basal
(single) fertilizer application methods in order to achieve reasonable crop yields
and reduce environmental threats in soils having a high nitrogen leaching
potential.
Table 2. Effect of application rate ofEDF and eRN on N loss and uptake in a sandy loam
Applied
-I
N uptake (kg ha )
N leaching (kg ha- I )
N
eRN
EDF
eRN
EDF
-I
(kg ha )
(NR!+)
(N03)
(NR!+)
(N03-)
100
93
35
46
119
150
115
42
46
161
200
123
50
47
201
250
125
55
48
244
300
129
61
49
286
400
129
67
54
374
3.3 Effect of Fertilizer Broadcasting and Banding on N Leaching
and N Uptake
Two types of soil (sandy loam and loam) and two types of fertilizer (ammoniumNand nitrate-N) were examined (Table 3). Band application of ammonium-N to a
sandy loam leads to significantly smaller N leaching as compared to broadcasting
due to the effect of nitrification inhibition caused by banding. Band application of
nitrate fertilizers in the sandy loam slightly reduces N leaching, and increases N
uptake in comparison to broadcasting. Banding also significantly reduces the
volatilization losses of ammonia due to a smaller area of contact with air and to
the band placement at a depth of 5 cm below the soil surface. The amount of N