Agriculture Reference
In-Depth Information
weight, grain yield, and grain harvest index (GHI) (Table 6.6). Hence, the response of these plant
characteristics is associated with an adequate rate of N, P, and K fertilization. Plant height varied from
24.33 cm in the N
0
P
0
K
0
treatment to 111.58 cm in the N
1
P
1
K
2
(N = 150 mg kg
−1
, P = 100 mg kg
−1
, and
K = 200 mg kg
−1
) treatment, with an average value of 74.92 cm. Shoot dry weight varied from 0.30 g
plant
−1
in the N
0
P
0
K
0
treatment to 28.66 g plant
−1
in the N
2
P
2
K
2
(N = 300 mg kg
−1
, P = 200 mg kg
−1
,
and K = 200 mg kg
−1
) treatment, with an average value of 10.65 g plant
−1
. Fageria and Baligar (1997)
reported a significant increase in rice plant height and shoot dry weight with the addition of N, P, and
K fertilization in the Brazilian Oxisol.
Grain yield varied from 0 to 23.01 g plant
−1
in the N
0
P
0
K
0
and N
2
P
2
K
2
treatments, respectively,
with an average value of 6.78 g plant
−1
(Table 6.6). Plants that did not receive P fertilization but
received adequate rates of N and K did not produce panicles or grains. Hence, it can be concluded
that P is the most yield-limiting nutrient in the highly weathered Brazilian Oxisol. Fageria and
Baligar (1997, 2001) have reported similar results. Grain yield results also showed that there
is a strong positive interaction among N, P, and K fertilization in upland production. This type
of interaction is widely reported in the literature (Wilkinson et al., 2000). These authors also
reported that increasing the N rate increases the demand for other nutrients, especially P and K,
and higher yields were obtained at the highest rates of N, P, and K. Wilson (1993) also confirmed
the generalization that the response to one nutrient depends on the sufficiency level of other nutri-
ents. Yield reductions were found when high levels of one nutrient were combined with low levels
of other nutrients (Wilkinson et al., 2000). Alleviating the yield-depressing effect of excessive
macronutrient supply involved removing the limitation of a low supply of other nutrients.
GHI varied from 0 in the treatment that did not receive P to 0.45 in the treatment N
2
P
2
K
2
, with
an average value of 0.25 (Table 6.6). GHI is an important index in determining the partitioning of
dry matter between shoot and grain. Fageria (2009) reported that rice GHI is influenced by envi-
ronmental factors, including mineral nutrition. Fageria and Baligar (2005) reported that variation
in rice GHI is from 0.23 to 0.50. However, Kiniry et al. (2001) reported that rice GHI values varied
greatly among cultivars, locations, seasons, and ecosystems, ranging from 0.35 to 0.62. The GHI
values of modern crop cultivars are commonly higher than for old traditional cultivars for major
field crops (Ludlow and Muchow, 1990). The limit to which GHI can be increased is considered to
be about 0.60 (Austin et al., 1980). Hence, cultivars with low harvest indices would indicate that
further improvement in the partitioning of a biomass would be possible (Fageria and Baligar, 2005).
On the other hand, cultivars with harvest indices between 0.50 and 0.60 would probably not benefit
by increasing the harvest index (Sharma and Smith, 1986).
Average response values of plant height, shoot dry weight, grain yield, and GHI with the appli-
cation of N, P, and K nutrients are presented in Table 6.7. Maximum plant height was achieved at
the N
1
level (150 mg N kg
−1
of soil), P
2
level (100 mg P kg
−1
of soil), and K
2
level (200 mg K kg
−1
of
soil). Similarly, shoot dry weight, grain yield, and grain harvest values were maximum at the high-
est levels of N
2
(300 mg kg
−1
of soil), P
2
(200 mg P kg
−1
of soil), and K
2
(200 mg kg
−1
of soil). The
increase in plant height was 25% at the N
2
level compared to the N
0
level. Similarly, the increase
in plant height at the P
2
level was 179% compared to the P
0
level and 25% at the K
2
level compared
to the K
0
level. Shoot dry weight increase was 191% at the highest N level compared to the lowest
N level; in case of P, the increase at the highest level was 1550% compared to the lowest P level.
Similarly, the increase in shoot dry weight at the highest K level was 55% compared to the zero
K level. Grain yield increase was 372% at 300 mg N kg
−1
compared to control treatment. At the
highest K level (200 mg K kg
−1
), the increase was 107% compared to control treatment. In case
of P at the zero P level, plants did not produce grain. The increase in harvest index at the highest
N, P, and K level followed the same pattern as the plant height, shoot dry weight, and grain yield.
Hence, it can be concluded that P was the most yield-limiting nutrient, followed by N and K in
upland rice production in Brazilian Oxisol. Fageria and Baligar (1997) and Fageria et al. (2010)
reported similar conclusions. The low availability of P in Brazilian Oxisol is associated with the
