Abstract:
The present study explores the impact of varying levels of biochar and carbonyl diamide (urea)
on the grain equivalent diameter, sphericity, volume, surface area, amylose, and iron content of
rice (Oryza sativa L.). This study aimed at exploring the potential benefits of biochar as a soil
amendment and its interactions with urea in influencing on physiochemical properties of rice
grains. Four distinct biochar (BC) levels (0, 1, 2 and 3 t ha-1) and partially burned paddy husk
(PBPH - 0.62 t ha-1) treatments were combined with varying urea levels (0, 30, 70 and 100 %)
following the recommended rate for paddy cultivation (225 kg ha-1) to assess the responses of
rice plants to different combinations following split plot experimental model at Rice Research
Station, Ambalantota. Using a manual husker, paddy samples from each treatment were dehusked
and the grain length and width were examined to ascertain the physical properties. Amylose
concentration was assessed by measuring the UV absorption value (620 nm) of the starch
solution. The UV (480 nm) absorption of the color developed solution (Fe2+) was used to measure
the iron concentration. Analysis of variance was performed using Statistix 8.1.1.0 software for
windows. The results revealed significant changes in grain physiochemical properties of rice in
response to different biochar and urea treatments. Conspicuously, the highest physicochemical
values were observed in rice plants treated with 70 % urea in aggregation with 2 to 3 t ha-1
biochar. These conditions induce a significant increase in equivalent diameter (2.70 mm),
sphericity (40.60 %), volume (10.62 mm3), surface area (3.15 mm2), amylose content (32.60 %),
and iron content (21.80 μg g-1) compared to the control treatment. These findings indicate that
specific combinations of biochar and urea have a synergistic effect on grain equivalent diameter,
sphericity, volume, surface area, amylose content, and iron content which lead to improve the
grain yield and nutritional composition. The results of this experiment demonstrated the
substantial effects of varying biochar and urea concentrations on the physicochemical
characteristics of rice grains. The aforementioned results provide important understanding
regarding the application of biochar as a sustainable soil supplement with urea to improve the
physicochemical characteristics of rice harvest.
