Abstract:
Biochar is a carbon rich material which enhances the soil health and improves the physiological performance of rice crops. It consists of a micro and nano size porous structure, which increases the soil’s nitrogen retention capacity. The study investigated the interaction effects of biochar and nitrogen fertilizer on nitrogen uptake, nitrogen utilization, nitrogen use efficiency and rice yield. The field experiment evaluated different nitrogen levels (0, 30, 70, and 100%) based on the recommended nitrogen dose of 105 kg ha-1, along with different rice husk biochar application rates (0, 1, 2, and 3 t ha-1). A split-plot experimental design with three replicates was used during the 2023 Yala and 2023/24 Maha seasons. Soil samples from each experimental unit were collected to determine the initial available nitrogen content. At the harvest, plant shoot and paddy samples of the AT 362 rice variety were analyzed to determine total nitrogen content which had used to calculate the nitrogen uptake efficiency (NUpE), nitrogen utilization efficiency (NUtE) and overall nitrogen use efficiency (NUE). Analysis of variances was performed by using Minitab 17 software. The results showed significant nitrogen uptake efficiencies of 71.04 and 69.15% in 2023 Yala and 2023/24 Maha seasons, respectively, with the highest value observed at 2 t ha-1 biochar and 70% nitrogen application rate. Similarly, NUtE (33.69, 33.32%) and NUE (28.56, 28.53%) were highest when 3 t ha-1 biochar and 70% nitrogen were applied in both seasons. Compared to the control treatment NUpE, NUtE and NUE were increased by 5.94%, 11.93% and 18.09%, respectively. Furthermore, significant raw paddy yields were recorded as 5.28 to 5.30 t ha-1 in 2023 Yala and 5.12 to 5.17 t ha-1 in 2023/24 Maha seasons with combine application of 2 to 3 t ha-1 biochar and 70 to 100% nitrogen fertilizer rates, which resulted to increase the grain yield by 11.36 to 13.87% and 8.78 to 9.67%, respectively, compared to treatments without biochar. These results emphasized the potential of combined biochar and nitrogen fertilizer application in improving nitrogen use efficiency in rice crops. The incorporation of biochar carbon in paddy production plays an important role in enhancing nitrogen retention and slow-release mechanisms, thereby improving crop yield performances.
