Abstract:
Nitrogen (N) is an essential plant nutrient being a component of amino acids, nucleic acids,
nucleotides, chlorophyll, enzymes, and hormones. It promotes plant growth yield and quality of
grains through increased tillering, leaf area development, grain formation, grain filling and
protein synthesis. Application of N fertilizer for rice facilitates growth as well as post-harvest
attributes of grains. A research study was conducted at research field of the Rice Research
Station, Ambalantota, Sri Lanka during 2019 yala season to investigate the effect of different
nitrogen application rates on grain quality, growth and yield parameters of rice. The experiment
was established with four nitrogen levels such as 50, 100, 150 and 200 kg N ha-1 along with
control treatment (0 kg N ha-1) under irrigated water condition and two red pericarps three month rice varieties (promising rice line At 13 2715 was developed by crossing between At 362
and PSPRC 28 and standard variety At 311). Treatments were arranged in a split plot design
with three replicates. The gross plot and net plot area of each experimental unit were 18 m2 and
the 12.96 m2. Main plots were separated by a ridge (40 cm in width). Phosphorus (45 kg ha-1
P2O5 - triple super phosphate) was applied at the basal fertilizer application and potassium (20
kg ha-1 K2O as Muriate of potash) was applied to all experimental plots after four and six weeks
from seed sowing. Grain yield (t/ha), plant height (cm), tiller count, filled and unfilled grain
count per panicle, spikelet count per panicle, 1000 grains weight (g) and straw weight (kg/12.96
m2) were determined. Analysis of variance was performed using STAR for Windows version
2.0.1. Different soil nitrogen application rates were responded differently on rice crop where
zero nitrogen level (0 kg N ha-1) was given the lowest response of both At 13 2715 and At 311.
Rice cultivated with higher rate of nitrogen (≥100 kg N ha-1) was given higher grain filling and
growth of both verities. Application of 100 kg N ha-1 rate was recognized as the significant level
for growth, yield and some yield contributing attributes. However, further increasing of soil
nitrogen (≥100 kg N ha-1) was not significantly (p ˃ 0.05) improved the growth, grain yield and
yield parameters of both rice varieties At 13 2715 and At 311.
