Key Takeaways
- Compost and BiocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More Mixtures Outperform Chemical Fertilizers. The study found that a 1:1 mixture of compost and biochar (CMP+BCH) yielded higher maize yields (304.2 kg/ha) than either the control group or the standard NPK inorganic fertilizer treatment. While compost alone released the most nutrients initially, the combined mixture provided superior long-term benefits for plant height, leaf area, and grain weight.
- Biochar Creates a “Slow-Release” Nutrient Mechanism. Unlike inorganic NPK fertilizers, which provide a rapid surge of nitrogen followed by a quick decline due to leachingLeaching is the process where nutrients are dissolved and carried away from the soil by water. This can lead to nutrient depletion and environmental pollution. Biochar can help reduce leaching by improving nutrient retention in the soil. More or volatilization, biochar-based treatments exhibit gradual, consistent nutrient release. The porous nature of biochar helps retain nitrogen and phosphorus in the soil, buffering against rapid depletion and ensuring nutrients are available when the crop actually needs them.
- Significant Improvements in Soil pHpH is a measure of how acidic or alkaline a substance is. A pH of 7 is neutral, while lower pH values indicate acidity and higher values indicate alkalinity. Biochars are normally alkaline and can influence soil pH, often increasing it, which can be beneficial More and Structure. The application of biochar and compost significantly improved soil quality in tropical acidic soils. The treatments neutralized soil acidity, raising the pH from strongly acidic levels (5.1) to near-neutral levels favorable for agriculture. Additionally, the mixture improved the Mean Weight Diameter (MWD) of soil aggregates, thereby enhancing soil structure, reducing erosion risk, and improving water infiltration.
- Timing of Application is Critical. To maximize results, the researchers recommend applying organic amendments 2–4 weeks prior to planting7. This lead time allows the mineralization process to begin, ensuring that peak nutrient release—specifically for phosphorus and potassium—aligns perfectly with the maize crop’s most critical growth stages around week 10.
- Biochar Enhances Long-Term Soil Fertility. While chemical fertilizers address immediate crop needs, they contribute little to long-term soil quality. The study identified the compost-biochar mixture as the most sustainable strategy because it improves Cation Exchange Capacity (CEC) and Organic Carbon (OC) levels. This stabilization of carbon leads to sustained fertility and nutrient retention over time, unlike the temporary boost provided by synthetic options.
A recent study by researchers from Federal University Wukari and Ahmadu Bello University evaluated the temporal effects of five soil amendments on nutrient release, soil quality, and maize performance. Conducted in the Alfisols of Zaria, Nigeria, the experiment compared compost (CMP), biochar (BCH), co-composted biochar (C-BCH), a compost-biochar mixture (CMP+BCH), and inorganic NPK fertilizer against a control group. The researchers utilized three Soil Quality Index (SQI) calculation methods—threshold, weighting, and Analytic Hierarchy Process (AHP)—to rigorously assess the integrated effects of these amendments.
Sustainable crop production in tropical regions faces significant hurdles due to poor soil fertility and low nutrient buffering capacity. While inorganic NPK fertilizers provide immediate nutrients, they are susceptible to rapid losses through leaching and volatilization, which can negatively affect soil structure over repeated applications. Specifically, the local soil in Zaria presented strong acidity and low levels of essential nutrients like nitrogen and phosphorus, requiring interventions that could balance immediate crop demands with long-term soil health.
To address these challenges, the research team implemented a randomized complete block design involving organic treatments applied at 15 tons per hectare. They monitored nutrient release (N, P, and K) bi-weekly over a 12-week period. The study aimed to identify an amendment strategy that not only supplied nutrients but also improved key soil quality indicators such as organic carbon (OC), cation exchange capacity (CEC), and mean weight diameter (MWD) of soil aggregates.
The results indicated that while compost initially released the most nitrogen, phosphorus, and potassium, the compost and biochar mixture (CMP+BCH) emerged as the superior amendment. This mixture significantly improved organic carbon content (1.89%) and cation exchange capacity (9.13 cmol kg⁻¹) while maintaining a near-neutral pH. These soil improvements translated to superior agricultural productivity, with the CMP+BCH treatment achieving the highest grain yield of 304.2 kg per hectare, surpassing both the NPK fertilizer and control groups. The biochar-inclusive treatments demonstrated a more gradual and consistent nutrient release pattern compared to the rapid surge and decline observed with NPK.
For the biochar industry, this study highlights the efficacy of combining biochar with compost to optimize nutrient use efficiencyNutrient use efficiency refers to how effectively plants can take up and utilize nutrients from the soil. Biochar can improve nutrient use efficiency by enhancing nutrient availability and retention in the soil. More in tropical soils. The data suggest that applying these amendments 2 to 4 weeks before planting allows peak nutrient release to coincide with critical crop growth stages. Furthermore, the study validates the use of threshold and weighting SQI methods for predicting crop productivity, offering a robust framework for future soil management assessments.
Source: Awwal, Y. A., Angyu, M. D., & Afolabi, R. J. (2025). Impact of various soil amendments on temporal NPK release, soil quality and maize yield in tropical Alfisols of Zaria, Nigeria. Scientific Reports, 15(41856).
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