Biochar-Mediated Controlled Release of Mineral Nitrogen From Urea Enhances Wheat Yield in Low Fertility Alkaline Soil

Abstract

Background

Nitrogen (N) losses in low-fertility alkaline soils substantially reduce nitrogen use efficiency and limit wheat productivity. Although biochar has been widely studied as a nutrient-retentive soil amendment; however, its potential to assist fertilizer reduction under alkaline soil conditions remains insufficiently understood.

Aim

This study evaluated the effectiveness of integrating biochar with urea to regulate soil N transformations and enhance wheat productivity in alkaline soil.

Method

A 1-month laboratory incubation study was conducted in soil amended with biochar at 1%, 2%, and 3% (w/w) and urea at the recommended rate of 150 kg N ha⁻¹ (0.0144 g urea jar⁻¹). In a complementary pot experiment, wheat was grown in alkaline soil amended with 1% biochar combined with urea applied at 100%, 85%, and 70% of the recommended rate (0.87, 0.74, and 0.60 g urea pot⁻¹), respectively.

Results

Results showed that 3% biochar was the most effective rate in the laboratory incubation, significantly lowering NH₄⁺-N concentration and delaying its nitrification to NO₃^–-N; however, on the basis of the practical applicability, 1% biochar was selected for the pot experiment. Results for pot experiment revealed that wheat plants receiving 85% of the recommended urea with 1% biochar displayed improved agronomic attributes and produced higher grain yield (15.5 g pot⁻¹) and total N in roots, shoots, and grain than plants supplied with 100% urea alone.

Conclusion

Overall, the results demonstrate that low biochar application rate (1%) can partially substitute for mineral N fertilizer by regulating urea-derived N dynamics and improving wheat performance in alkaline soil.