Effect of straw biochar application on soil carbon, greenhouse gas emissions and nitrogen leaching: A vegetable crop rotation field experiment

Intensive vegetable crop systems are rapidly developing, with consequences for greenhouse gas (GHGs) emissions, nitrogen leaching and soil carbon. We undertook a field trial to explore the effect of biochar application (0, 10, 20 and 40 t ha(-1)) on these factors in lettuce, water spinach and ice plant rotation. Our results show that the 20 and 40 t ha(-1) soil treatments resulted in the SOC content being 26.3% and 29.8% higher than the control (0 t ha(-1)), respectively, with significant differences among all treatments (p < .05). Biochar application caused N2O emissions to decrease during the lettuce and water spinach seasons, by 1.5%-33.6% and 12.4%-40.5%, respectively, compared the control, with the 20 t ha(-1) application rate resulting in the lowest N2O emissions. Biochar also decreased the dissolved nitrogen (DN) concentration in leachate by 9.8%-36.2%, following a 7.3%-19.9% reduction in dissolved nitrogen in the soil. Similarly, biochar decreased the nitrate (NO3-) concentrations in leachate by 3.9%-30.2%, following a 3.8%-16.7% reduction in the soil nitrate level. Overall, straw biochar applied at rate of 20 t ha(-1) produced the lowest N2O emissions and N leaching, while, increasing soil carbon.