Rice genotype affects nitrification inhibition in the rhizosphere

Abstract

Aims

Biological nitrification inhibitors (BNIs) can play an important role in inhibiting nitrification and enhancing nitrogen use efficiency (NUE) in agriculture. However, most current BNI studies have been conducted under hydroponics. Genotypic differences in the inhibition of nitrification in soil are still largely unknown. Our main aim was to investigate the regulation of N transformation processes by different rice genotypes with different BNI release potentials on NUE and N loss.

Methods

Two rice genotypes, i.e. Wuyujing 3 (WYJ3) and Wuyunjing 7 (WYJ7), reported to have weak and strong BNI capacity, respectively, under hydroponic conditions, and four soils with different pH (i.e. JX (pH 5.09), FJ (pH 6.00), SC1 (pH 7.96) and SC2 (pH 7.94)) were selected for this study. Plant N uptake rates (esp. NH₄⁺ uptake, U_NH4) and soil N transformation rates were quantified by ¹⁵ N tracing to assess the effects of rice genotypes on nitrification inhibition activity. NUE and N loss were quantified in a separate ¹⁵ N-urea labeling experiment.

Results

The results showed that the rice genotype with high BNI exudation (i.e. WYJ7) had lower autotrophic nitrification rate (O_NH4) and higher U_NH4 compared to WYJ3. O_NH4 in WYJ7 decreased by 0.05, 0.42, 1.14, and 0.48 mg N kg⁻¹ d⁻¹ compared to WYJ3 for JX, FJ, SC1 and SC2, respectively. The abundance of AOB in soils planted with WYJ7 was lower than in soils planted with WYJ3, which was the most important factor to explain the variation of O_NH4. WYJ7 tends to have a relatively higher NUE than WYJ3 in JX, SC1 and SC2. NUE was negatively correlated with O_NH4.

Conclusion

Our results indicate that some rice genotypes can optimize their N acquisition by regulating soil N transformations (especially nitrification). The development of rice genotypes with strong BNI exudation capacity could be a suitable management practice to increase NUE and yield.