Agriculture Reference
In-Depth Information
FIGURE 1.15
Root growth of upland rice genotype BRA 052045 without and with N (300 mg N kg
−1
). Half
of the N was applied at sowing and the remaining half at 45 days after sowing.
The author studied the influence of different N rates and three sources on root growth of low-
land rice. The maximum root length (MRL), root dry weight, and the contribution of root to the
total plant were significantly affected by N treatments (Table 1.15). The MRL varied from 16.25
to 27.25 cm, with an average value of 21.27 cm. In case of ammonium sulfate and common urea,
the MRL decreased with increasing N rate but in case of polymer-coated urea it increased. The
decrease in root length at higher N rate has been reported by Fageria and Moreira (2011). However,
root length is genetically controlled and may vary from genotype to genotype. The root dry weight
increased with the addition of N fertilizer and varied from source to source. The increase in root dry
weight was quadratic in case of ammonium sulfate (Table 1.16) and maximum root dry weight was
achieved with the application of 279 mg N kg
−1
soil. In case of common urea and polymer-coated
urea, the increase in root dry weight was linear (Table 1.16) with an increasing N rate in the range
of 0-400 mg N kg
−1
soil. Overall, the maximum root dry weight was higher at the highest N rate
(400 mg N kg
−1
) treatment. The improvement in the root dry weight of rice with the addition of rice
has been reported by Fageria (2013).
Figures 1.16 through 1.18 show the root growth of lowland rice under different N rate and N
sources. It can be seen from these figures that root growth was higher with the addition of N com-
pared to control treatment with three N sources. In addition, root growth also varied with N source.
The contribution of root in the total plant weight varied from 7.54% to 16.79%, with an average
value of 12.50%. Fageria and Moreira (2011) reported that the contribution of the root in total plant
weight varied with genotype and was also affected by fertilization, including N. However, the aver-
age contribution of the root in the total plant weight is less than 20%. Results of the present study
fall within this limit.
The author studied the influence of N rates on the root growth of corn (Table 1.17). MRL was
obtained at the lowest N rate and the minimum at the highest N rate. The decrease in root length was
quadratic with increasing N rate in the range of 0-600 mg N kg
−1
. The variation in the root length
