Agriculture Reference
In-Depth Information
TABLE 6.7
Average Values of Plant Height, Shoot Dry Weight, Grain Yield, and Grain Harvest Index
across N, P, and K Levels
N, P, and K
Treatments
Shoot Dry Weight
(g Plant
−1
)
Grain Yield
(g Plant
−1
)
Plant Height (cm)
Grain Harvest Index
N
0
65.55b
5.20c
2.19c
0.21b
N
1
81.68a
11.61b
7.83b
0.27a
N
2
78.53a
15.12a
10.33a
0.27a
Average
74.92
10.65
6.78
0.25
P
0
34.35b
1.02c
0.00c
0.00b
P
1
94.85a
12.11b
8.98b
0.37a
P
2
95.56a
16.83a
11.37a
0.37a
Average
74.92
10.65
6.78
0.25
K
0
67.00b
8.18b
4.23b
0.23a
K
1
76.34a
11.08a
7.38a
0.25a
K
2
81.41a
12.69a
8.75a
0.27a
Average
74.92
10.65
6.78
0.25
Note:
Means within the same column and same nutrient levels followed by the same letter do not differ significantly at the
5% probability level by Tukey's test.
natural low level of this element and higher P immobilization capacity (Fageria, 1989; Fageria and
Baligar, 2008).
Panicles per plant were significantly influenced by N, P, and K treatments and their interactions
(Table 6.8). The 1000 grain weight was also influenced by N, P, and K treatments and N × P and
N × K interactions. Root dry weight was influenced by N, P, and K treatments and N × P, N × K, and
P × K interactions. This means that for obtaining the maximum panicle number, 1000 grain weight,
and root dry weight, there is need for an adequate level of N, P, and K in the growth medium.
Average analysis of N, P, and K showed the maximum effect of P on the panicle number, followed
by N and K (Table 6.9). Root dry weight and maximum root length were influenced by N and P
treatments. The K application improves these parameters but the effect was not significant. Spikelet
sterility was reducing with the application of K compared to the control treatment. The improve-
ment in panicle number, 1000 grain weight, and root growth with the application of N, P, and K has
been reported by Fageria et al. (2010) and Fageria (2009).
The N, P, and K interactions were also observed in the growth of rice plants. Plants that did not
receive N, P, and K fertilization (N
0
P
0
K
0
) had a significantly lower height, did not produce tillers,
and also did not produce grain (Figure 6.4). Similarly, plants that did not receive N and P but only
K also did not produce grain or tillers, and the height was significantly reduced (Figure 6.4). Rice
growth was significantly improved with increasing N rates from 0 to 300 mg N kg
−1
along with
P and K 200 mg kg
−1
of soil (Figure 6.5). Plants with adequate P
200
and K
200
but which did not
receive N were yellow in color, with reduced tillering, and had few panicles (Figure 6.5). Increasing
P levels from 0 to 200 mg kg
−1
significantly improved the rice growth, tillering, and panicle number
(Figure 6.6). However, plants without P did not produce panicles or grains (Figure 6.6). The plants
that received adequate amounts of N and K but did not receive P had leaves that were dark green
and straight (Figure 6.6), indicating that P deficiency is the most yield-limiting factor in Brazilian
Oxisols. The K-deficient plants produced yellow leaves whose margins and tips were dry (Figure
6.7). Potassium symptoms first started on older leaves, and with time the whole plant was showing
K deficiency symptoms. Maturity was delayed by about 10 days in pots that did not receive K but
