Agriculture Reference
In-Depth Information
N
1
P
1
K
0
N
1
P
1
K
2
FIGURE 6.8
Root growth of upland rice at different N, P, and K levels. (N
1
P
1
K
0
= N
1
, 150 mg N kg
−1
;
P
1
, 100 mg P kg
−1
; K
0
, 0 mg K kg
−1
; and K
2
, 200 mg K kg
−1
.)
2005). Wilkinson et al. (2000) reported that plants supplied with NO
3
-N accumulate more cations
(K, Ca, and Mg), while those supplied with NH
+
accumulated more anions (SO
4
2−
, H
2
PO
−
, Cl
−
).
Wilkinson et al. (2000) also reported that when N is supplied as NH
+
, it may decrease the uptake
of cations such as Ca
2+
. However, in well-drained or oxidized soils, NO
3
-N is the major form of N
uptake. In flooded rice, nitrogen may be present in NH
+
form in the reduced soil layer due to lack
of oxygen, which inhibits nitrification. Under this situation, there may be a negative interaction
between N and Ca
2+
.
The use of lime and farmyard manures significantly increased water-soluble N and fixed NH
+
in acid soils of India, leading to increased N uptake by soybean and wheat (Bishnoi et al., 1984;
Prasad et al., 1986). In a highly acidic soil (pH 4.5), a substantially higher rice yield obtained with
the combined application of lime and NPK than NPK or lime alone indicated that soil acidity is
the main constraint in the utilization of nutrients by the crop (Fageria and Baligar, 2001). Once
acidity is corrected, the uptake of soil N, Ca, and some other nutrients registered a multifold
increase. Other associated problems, such as high concentrations of Al and Mn, reduced biologi-
cal nitrogen fixation in legumes, and decreased root growth, may lead to a decline in water and
nutrient use efficiencies (Aulakh and Malhi, 2005). Malhi et al. (1995) reported that with the
application of lime with an adequate rate of N, there was a significant yield increase of barley and
also improved NUE.
TABLE 6.10
Influence of N on the Uptake of Ca in the Shoot
of 60-Day-Old Dry Bean Plants
N Rate (kg ha
−1
)
Ca Uptake (kg ha
−1
)
0
4.1
40
8.2
80
12.8
120
12.9
160
18.4
200
24.9
R
2
0.79**
**Significant at the 1% probability level.
