Arid and semi-arid soils are low in organic matter and have poor fertility, making them a serious threat to crop production. Most organic amendments, such as crop residues and farmyard manure, are short lived because of rapid decomposition. Incubation and pot studies were conducted to assess the impact of wheat straw biochar (produced at 350 °C) on temporal changes in soil microbial biomass and fertility status and to evaluate the efficacy of biochar for maize production in the top layer of Typic calciargid. The incubation study compared four levels of biochar (control, 0.5, 1.0 and 2.0% on a w/w basis of soil) and two fertilizer rates, i.e., unfertilized (no NPK fertilizer) and fertilized (nitrogen, P₂O₅ and K₂O with rates of 125, 80 and 52.5 mg kg⁻¹ soil, respectively). After incubation, the 2.0% biochar significantly improved the soil cation exchange capacity, organic carbon and microbial biomass carbon by up to 35, 59 and 26%, respectively, while decreasing the soil pH by up to 1.5% compared to that of the control treatment. When fertilized, the 2.0% biochar improved the soil’s available phosphorous, extractable potassium and total nitrogen by up to 59, 39 and 28%, respectively, compared to those of the control. The results from the pot experiment showed that using the 1% biochar with fertilizer significantly increased the maize dry biomass and grain yield by up to 57 and 72%, respectively, compared to those of the control. Additionally, the nitrogen and phosphorus recoveries from the mineral fertilizers improved significantly (up to 26 and 38%, respectively) when using the 1.0% biochar compared to those of the control. Conclusively, the addition of 1.0% biochar significantly improved maize growth and yield by enhancing nutrient recovery from mineral fertilizer and improving soil properties.

Non-nutritive metals, especially cadmium (Cd), are present in P fertilizers; the long-term application of these P fertilizers leads to Cd build-up in the soil. The current study aims to evaluate the impacts of P sources and rates on the growth of maize (Zea mays L.) and the bioavailability of Cd. Twelve treatments including rock phosphate 4 g kg⁻¹ (RP1); 8 g kg⁻¹ (RP2); 12 g kg⁻¹ (RP3)); single super phosphate 333 mg kg⁻¹ (SSP1); 444 mg kg⁻¹ (SSP2); 555 mg kg⁻¹ (SSP3); di-ammonium phosphate 130 mg kg⁻¹ (DAP1); 174 mg kg⁻¹ (DAP2); 218 mg kg⁻¹ (DAP3); mono-ammonium phosphate 115 mg kg⁻¹ (MAP1); 154 mg kg⁻¹ (MAP2); 193 mg kg⁻¹ (MAP3) in two soil textures (sandy and clayey) were assessed. Results revealed that all P sources significantly influenced the plant growth and yield characteristics of maize (p ≤ 0.05). In both soil textures, P in soil and plant, plant growth and yield characteristics were maximized by MAP and DAP. Cadmium build-up in soil and uptake was also significantly (p ≤ 0.05) affected by P sources, levels, and soil texture. It was observed that Cd build-up in soil and uptake by plants boosted with increasing P levels. Maximum Cd concentration in plant root and shoot was found with SSP3, and its concentration in soil increased with MAP3, whereas the concentration was higher in sandy texture. The study concludes that type of P fertilizer should be determined based on texture and human consumption of the crop to avoid Cd toxicity.

Soil fertility in arid to semi-arid regions is constrained by extreme temperature fluctuations. Soils of such regions typically have low fertility levels, nitrogen (N) availability (due to ammonia volatilization and denitrification), and soil organic carbon (SOC) content. An incubation experiment was conducted to assess how a peanut-waste biochar (PB), produced at 300°C, influences the mineral N and chemical properties of an alkaline soil. The treatments included five PB rates (control, 5, 10, 15, and 20g PB kg⁻¹ soil) and two fertilizer rates [no fertilization without additions of N and phosphorus (P) and fertilization with addition of 120kg N ha⁻¹ and 90kg P ha⁻¹]. The soil was incubated for various durations (0, 14, 28, 42, and 56days). There were significant temporal shifts in the mineral form of N in the incubated soil. Following 56days of incubation under fertilization, the treatment with 20g kg⁻¹ PB revealed soil nitrate-N and ammonium-N levels of 15.8mg kg^‒1 and 21.1mg kg^‒1, respectively. With no fertilization, 20g kg⁻¹ PB increased mineral N by 2.3-fold over the treatment without PB. This increase was 2.6-fold with fertilization. After 56days of incubation, in the presence of 20g kg⁻¹ PB, there was a 19% increase in cation exchange capacity under fertilization and a 21% increase under no fertilization, compared to the respective treatments without PB. Immediately after the PB application, SOC was significantly increased, corresponding to PB rates. However, substantial increases were observed only in treatments with 15 and 20g PB kg⁻¹ soil. In conclusion, the addition of 15 and 20g PB kg⁻¹ to alkaline soil significantly increased N availability in soil, demonstrating the importance of biochar for N management in agricultural soils.

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.