Low-temperature produced peanut-waste biochar reduced nitrogen and phosphorous fertilizer dependency of maize hybrid Syngenta-6621 in alkaline soil

Slow pyrolyzed, low-temperature (300-350⁰C) produced biochar can be used for improving chemical characteristics of nutrient-deficient alkaline soil, however, the effect of such type of biochar on crop fertilizer demand is poorly understood. Thus, a pot experiment was carried out to determine the optimal nitrogen (N) and phosphorus (P) fertilizer requirements for maize grown in peanut-factory waste biochar (PBC) amended calcareous soil. The experiment used a completely randomized design, where two treatments were applied without PBC: one with no N or P fertilizer (control) and one with the recommended doses of NP fertilizer (N3P3). In addition, sixteen treatments were applied with 1.5% PBC, incorporating all possible combinations of four N fertilizer levels (0%, 33%, 66%, and 100% of the recommended dose, labelled as N0, N1, N2, and N3) and four P levels (0%, 33%, 66%, and 100%, labelled as P0, P1, P2, and P3). The N3P3 treatment served as the baseline for evaluating maize growth stages. Three replicates for each treatment were harvested randomly at the V8 growth stage (after 25 days of germination based on N3P3), while the remaining three replicates were harvested at the V14 stage (after 50 days of germination based on N3P3). At V8, the PBC + N3P2 treatment resulted in a significant increase (24%) in shoot fresh weight compared to N3P3. The highest increases in shoot P concentration (25%) and uptake (20%) were observed in the PBC + N1P2 and PBC + N3P3 treatments, respectively, compared to N3P3. By the V14 stage, the PBC + N2P2 treatment yielded maximum value of dry matter (17.7 g pot−1) and had 18% more shoot dry matter than N3P3. Additionally, this treatment showed the largest improvement (10%) in chlorophyll content. In terms of N, the PBC + N3P0 and PBC + N3P2 treatments had the highest concentration (19%) and uptake (37%), respectively, compared to N3P3. Treatment PBC + N2P2 also recorded the highest P concentration and uptake, with increases of 16% and 34%, respectively, over N3P3. Growth rates were significantly higher when PBC was used without additional N or P fertilizer, compared to the N3P3 treatment. The results at V14 suggest that applying 1.5% slow pyrolyzed, low-temperature PBC can reduce N and P fertilizer requirements by up to 34% without negatively affecting the nutrient content or uptake in fodder maize.