# Combined Impacts of Nitrogen Forms, Rice Husk Biochar, and Water Regime on Purple Rice Yield and Grain Quality

## TL;DR

This study shows how water, biochar, and nitrogen types affect purple rice yield and quality, finding that flooded conditions with biochar and certain fertilizers give the best results.

## Contribution

The study reveals the combined effects of water regime, biochar, and nitrogen sources on purple rice productivity and nutritional quality.

## Key findings

- Flooded conditions with biochar and urea or ammonium produced the highest grain yield and quality.
- Nitrate use in non-flooded fields without biochar led to the lowest yields and grain quality.
- Biochar and water applications maximized grain phenol content and antioxidant capacity.

## Abstract

Purple rice is valued for its beneficial bioactive compounds, but the levels of these compounds depend on how the rice is grown. This study explored how different combinations of water management, rice husk biochar amendment, and nitrogen fertilizer types affect the yield and grain quality of purple rice. Results showed that purple rice grown under flooded conditions with added biochar and either urea or ammonium produced the highest grain yield and yield components, such as plant height, number of spikelets per panicle, and the percentage of filled grains. On the other hand, using nitrate, especially in non-flooded fields without biochar, led to the lowest yields and grain quality. Patterns of shoot nitrogen content were similar to grain yield changes. Interestingly, the highest grain nitrogen concentration was found in non-flooded conditions, regardless of whether biochar or urea/ammonium was applied. Anthocyanin content in the grain, which gives it the purple color and has health benefits, was maximized under flooded conditions, particularly when biochar and nitrate or ammonium (without biochar) were used. Grain phenol content and antioxidant capacity were highest when biochar and water were applied. Overall, using rice husk biochar can boost productivity without affecting the color shade of purple rice, but its effects on nutritional qualities are more complex.

Purple rice contains beneficial bioactive compounds, but the concentrations can be influenced by the growing conditions. This study investigated the interactive effects of water regime, biochar amendment, and nitrogen (N) sources on the yield and grain quality of purple rice. Purple rice grown under flooded conditions combined with biochar and urea or ammonium demonstrated significant increases in grain yield and yield components such as plant height, number of spikelets per panicle, and the percentage of filled grains compared to non-flooded conditions. Nitrate consistently resulted in the lowest yields and grain quality, especially under non-flooded conditions and with no added biochar. Grain anthocyanin concentration was highest under flooded conditions, with the maximum observed with biochar and nitrate application and with ammonium application without biochar. In contrast, the grain phenol content and antioxidant capacity were maximized by the biochar and water applications. The findings indicate that rice husk biochar can improve productivity without altering the color shade of purple rice. Combining flooding, biochar, and ammonium or urea improves the agronomic performance of purple rice, though the impact on nutritional qualities is more complex.