Yoshida - 1981 - Fundamentals of Rice Crop Science

MINERAL NUTRITION OF RICE 127
Table 3.9. Effect of soil temperature on nutrient uptake by the rice plant. a
Temperature
Nutrient uptake (mg/150 seedlings per 48 h)
P 2 O 5 SO 3 CI NH 4 -N K 2 O MgO CaO H 2 O
30°C (A) 39.0 16.5 22.3 19.3 38.1 8.7 4.9 73.8
16°C (B) 21.8 12.0 25.0 13. 2 28. 4 7.7 5.7 49.1
B/A x 100 56 71 112 68 79 88 116 67
a Takahashi et al (1955).
SO
2-
4 , and the solution pH decreases sharply.
When NH
+
4 and NO
-
3 are available, the rice plant prefers NH
+
4 , and the
solution pH decreases. Later, however, the solution pH increases as NO
-
3 is
absorbed.
The relative absorption rate of cations by the rice plant appears to follow the
order:
Among anions, it appears to be:
NH
+
4 > K > Mg 2+ > Ca 2+ (3.12)
+f
NO 3
–
> H 2 PO 4
–
> CI – > SO 4
2–
. (3.13)
Fertilizers are sometimes classified as physiologically acid and physiologically
basic. Physiologically acid fertilizers refer to those that would make soil acidic as a
result of the plant's selective absorption of a fertilizer component. Ammonium
sulfate and ammonium chloride are physiologically acid. Calcium nitrate is
physiologically basic.
Table 3.10. Changes in solution pH caused by selective
absorption of ions by the rice plant. a
Nutrient
Solution pH
Initial 2nd day 5th day
Ca(NO 3 ) 2
5.83
CaCI 2
5.85
CaSO 4
5.89
CaH 4 P 2 O 8
4.20
NH 4 NO 3
5.82
NH 4 CI
5.83
(NH 4 ) 2 SO 4
5.81
NH 4 H 2 PO 4
5.00
KC I
5.83
MgCl 2 5.83
a Ishizuka and Tanaka (1969).
8.55
5.85
5.70
5.21
3.05
3.00
2.85
3.05
4.60
5.63
9.18
6.40
5.40
5.23
5.45
2.85
2.55
3.00
4.40
4.90