An Analysis of the Nitrogen Dynamic Impacted by Biochar and Compost on Ultisol Soil Using Stable Isotope N-15

Biochar has been proposed as a potential environmental-friendly soil amendment to increase soil quality and crop production and reduce chemical fertilizer use, especially in low-fertility soils. The combination of biochar with other soil amendment materials, namely compost, is carried out to increase the efficiency of nitrogen fertilizers, in particular on Ultisol soil. An experiment using the isotope stable 15N technique was conducted to investigate the effects of rice husk biochar, compost, and urea fertilizer on nitrogen efficiency, soil pH, EC, and maize production. The pot experiment was designed using Completely Randomized Design, and the treatments were: (1) control; (2) 50% urea; (3) 50% urea + biochar; (4) 50% urea + compost; (5) 50% urea + biochar + compost; (6) 100% urea; (7) 100% urea + biochar + compost. The results showed that combined biochar and compost significantly increased N-uptake derived from 15N-labelled fertilizer, total N uptake by plants, 15N plant recovery, and soil 15N residues, and decreased 15N loss compared to urea alone. This treatment also significantly increased the grain yields and total biomass of the maize plants.