Agriculture Reference
In-Depth Information
found by Kizito et al. (2007) who showed no competition for water between shrubs and millet and a
significantly higher soil moisture profile in millet-shrub intercrop plots than in sole millet plots on
the same experimental plots (Dossa et al., 2012). Additionally,
Guiera senegalensis
could have been
providing water by performing hydraulic lift (Richards and Caldwell, 1987) of water from the wet
subsoil to the dry surface soil as shown by Kizito et al. (2007).
2.9.13 u
se
of
n
atural
z
eolIte
Among the effective solutions for minimizing N losses from soil-plant systems, the use of natural
minerals such as zeolite has been recommended (Gholamhoseini et al., 2012). Zeolites are hydrated
aluminosilicates, characterized by a three-dimensional network of SIO
4
and AlO
4
, which are linked
by shared oxygen atoms. Partial substitution of silicon and aluminum results in an excessive nega-
tive charge, which is compensated by cations (Gholamhoseini et al., 2012). These cations are located
with water molecules in the cavities and channels inside the aluminosilicate framework. Water and
cations can be removed or replaced by other cations (Rehakova et al., 2004; Murphy et al., 2005).
Selective absorption and controlled release of cations by zeolite enhances nutrient availability and
improves plant growth and development (Gholamhoseini et al., 2012).
Zeolite has certain unique features such as high cation-exchange capacity (200-300 cmol
c
kg
−1
)
(Leggo et al., 2006), selective absorption, slow release of ammonium (He et al., 2002), and structure
stability over the long term (Huang and Petrovic, 1994). Regarding zeolite availability, Mumpton
(1999) reported that extensive deposits of zeolite have been found in western United States, Bulgaria,
Hungary, Japan, Australia, China, and Iran. In Iran, the cost of zeolite is approximately 2.5 cents
(U.S.)/kg; so, the application of zeolite would be economical (Gholamhoseini et al., 2012). Many stud-
ies have reported that the use of zeolite with organic fertilizers improved their efficiencies in crop pro-
duction (Daryaei et al., 2011; Khodaei et al., 2012). Hence, it is expected that the application of zeolite
with chemical fertilizers, especially N fertilizers, can increase efficiency of use and optimize chemi-
cal fertilizer use (Gholamhoseini et al., 2012). Gholamhoseini et al. (2012) reported that a combined
application of zeolite and chemical N for canola (
Brassica napus
L.) production in a poor sandy soil
is recommended to ensure an acceptable forage yield and soil protection from excess N leaching loss.
2.9.14 C
alCIum
s
tImulates
a
mmonIum
a
BsorptIon
Calcium ion in soil solution in an adequate amount was reported to increase
NH
4
+
absorption by plants
(Horst et al., 1985; Taylor et al., 1985; Fenn et al., 1987, 1994). Strong substantiation for the use of Ca
2+
to increase plant growth, in the presence of
NH
4
+
, was reported by Sung and Lo (1990). They showed
that tillering and seed weight of rice substantially increased with increasing Ca
2+
concentration. These
authors concluded that the increase in plant growth was related to an increase in photosynthetic activ-
ity. Robinson and Baysdorfer (1991) also reported an increase in photosynthetic activity with the addi-
tion of
NH
4
+
along with calcium in soybean. Plant yields were increased in calcareous soils where
Ca
2+
was applied with urea, compared with yield from plots fertilized with urea alone, NH
4
NO
3
, or
other common N fertilizers (Horst et al., 1985; Taylor et al., 1985; Fenn, 1986; Fenn et al., 1987). The
Ca
2+
concentrations needed to enhance absorption in calcareous soils were above those normally con-
sidered necessary for adequate plant nutrition (Fenn et al., 1994). Fenn et al. (1991, 1994) and Fenn
and Miyamoto (1981) reported that calcium might stimulate metabolite transfers within plants and
enhance photosynthesis. The higher uptake of
NH
4
+
in the presence of Ca
2+
may reduce the conversion
of ammonium into
NO
3
−
; hence, less leaching or loss of N from soil-plant system.
2.9.15 a
doptInG
a
pproprIate
I
nterCroppInG
Adopting the appropriate intercropping in the cropping system is an important strategy in improv-
ing N losses from soil-plant system and improving their efficiency. Intercropping is an agricultural
