Agriculture Reference
In-Depth Information
5
(NH
4
)
2
SO
4
(Y) = 1.9132EXP
(0.00093X + 0.000031X
2
)
4
R
2
= 0.5296**
3
2
CO(NH
2
)
2
(Y) = 1.1194 + 0.0135X - 0.000024X
2
R
2
= 0.4122**
1
0
50
100
150
200
250
300
350
400
Nitrogen application rate (mg kg
-1
)
FIGURE 8.16
Root dry weight of upland rice as influenced by two nitrogen sources. (From Fageria, N. K.,
A. Moreira, and A. M. Coelho. 2011b.
J. Plant Nutr
. 34:361-370. With permission.)
to urea. Rice is an acid-tolerant plant and its growth was linearly increased when Al satura-
tion in the Brazilian Oxisol soil was increased from 0% to 30% (Fageria et al., 2011a). Data in
Figure 8.16 show that the response of root growth to N sources was different. Ammonium sulfate
produced much higher root growth at the lower N rate (<75 mg kg
−1
) and at the higher N rate
(250 mg N kg
−1
).
8.3.2 u
se
of
a
pproprIate
m
ethods
of
n
ItroGen
a
pplICatIon
Nitrogen is a mobile nutrient in the soil-plant system and it is different from P and K, which are
immobile in the soil-plant system. Hence, it can be moved from a distance to plant roots and can
be absorbed. However, if it is broadcast and there is no rainfall or irrigation, it may lead to loss due
to evaporation or volatilization. Hence, application in the band or incorporating into the soil may
reduce its loss and improve N use efficiency (Fageria, 2009). Campbell et al. (1995) also reported
that the banding of N fertilizers is superior to broadcasting. Fertilizer banded with the planter, also
known as starter fertilizer, is a common practice in Minnesota for corn (Kaiser and Kim, 2013).
Research with N banded to the side and below the seed has shown positive yield benefits for soybean
(Osborne and Riedell, 2006). Banding fertilizer with the planter can save on application costs of
broadcast fertilizer, which is commonly spread before the crop sowing.
In furrow placement of fertilizer is attractive to growers because of the potential to increase
nutrient availability (Mengel et al., 1988). The most commonly banded nutrients are N, P, but K and
S are also included in some sources commonly used (Kaiser and Rubin, 2013a,b). In furrow place-
ment is often justified for its potential to stimulate early growth, although responses in grain yield
are not always seen (Kaiser et al., 2005; Kim et al., 2013). Additionally, using a starter fertilizer with
a high N/P ratio can enhance P absorption by reducing soil P immobilization (Kaiser and Rubin,
2013a). Placing ammonium polyphosphate fertilizer in a band with the seed resulted in increased
plant biomass and a higher concentration of P in plant tissue compared with deeper band placement
(Mengel et al., 1988). Furrow application of N has been reported to be beneficial to increase the
biomass of corn (Bermudez and Mallarino, 2004) and soybean (Kaiser and Rubin, 2013a).
Total N plus K applied is typically used to make suggestions on how much fertilizer can be
safely applied with the seed (Kaiser and Rubin, 2013b). It is commonly recommended that in furrow
