Agriculture Reference
In-Depth Information
TABLE 8.2
Values of Soil pH and Ca
2
+
and Mg
2
+
Contents after
Harvest of Eight Crops (Upland Rice, Common
Bean, Corn, and Soybean) Grown in Rotation for
4 Years on a Brazilian Oxisol at Two Soil Depths
Lime Rate
(Mg ha
−
1
)
pH in
H
2
O
Ca
2
+
(cmol
c
kg
−
1
)
Mg
2
+
(cmol
c
kg
−
1
)
0-20 cm Soil Depth
0
5.6
1.9
1.0
4
6.0
2.3
1.1
8
6.2
3.0
1.2
12
6.4
3.1
1.2
16
6.5
3.3
1.3
20
6.8
3.8
1.4
20-40 cm Soil Depth
0
5.5
1.7
0.9
4
5.9
1.9
1.0
8
6.1
2.3
1.1
12
6.2
2.4
1.1
16
6.3
2.6
1.2
20
6.7
3.3
1.3
Source:
Adapted from Fageria, N. K. 2001.
Pesq. Agropec. Bras
.
36:1419-1424.
efficiently compared to sensitive plant species (Fageria, 2013). Plants respond to environmental
stresses by reprogramming various physiological processes, including selective ionic absorption,
which reduces ion toxicity, and the accumulation of osmoregulation substance to maintain continu-
ous water absorption at a low soil water potential. It has been shown that plants respond differently
to alkaline salts (NaHCO
3
and Na
2
CO
3
) and neutral salts (NaCl and Na
2
SO
4
) (Yang et al., 2007).
Guo et al. (2010) compared the response of wheat seedlings to saline and alkaline stress, and
showed that alkaline stress inhibits fructan synthesis, while saline stress increases it. Yang et al.
(2008) reported that
Suaeda glauca
had similar osmotic adjustment responses to saline and alka-
line stresses in shoots, including the accumulation of proline, organic acids, and inorganic ions, but
the mechanisms governing ionic balance under these stresses were different. Under saline stress,
Suaeda glauca
accumulated more inorganic ions than organic acids, while it was the reverse under
alkaline stress. Islam et al. (2011) reported that Na concentration in leaves of foxtail millet (
Setaria
italica
L.) and proso millet (
Panicum miliaceum
L.) was increased two times by alkaline than in
saline stress. However, the tolerance to alkaline stress was different between the two millet spe-
cies, with higher tolerance in proso millet than in foxtail millet. In rice, the inorganic anions were
dominant in maintaining intracellular ionic equilibrium under salt stress; however, organic acids,
especially malate and citrate, were the dominant components in maintaining intracellular ion bal-
ance under alkaline stress (Wang et al., 2011).
Lv et al. (2013) studied the effects of saline-alkaline stress in rice and found that seed germina-
tion is most strongly affected by osmotic stress, indicating that water availability is the determin-
ing factor for rice seed germination under saline-alkaline stress. Meanwhile, seedlings grew the
least under alkaline stress, which may be ascribed to severe cellular injury in the root system in
addition to ion toxicity from high salinity. The alkaline treatment significantly reduced the total
