Assessment of the impact of biochar amendments on soil organic carbon sequestration and crop yield under drought conditions in a semi-arid agroecosystem

Project Abstract

Biochar amendments were evaluated for their effectiveness in enhancing soil organic carbon (SOC) sequestration and sustaining crop yield under drought conditions in a semi-arid agroecosystem. The study deployed a randomized complete block design with four biochar application rates (0, 5, 10, and 20 t ha-1) and three soil texture-based sites representing loamy sand, loam, and silt loam, over two consecutive growing seasons. Key soil physico-chemical properties measured included SOC concentration, soil pH, cation exchange capacity (CEC), bulk density, and soil moisture retention. Plant performance was assessed through grain yield, aboveground biomass, harvest index, and water use efficiency (WUE). Drought stress was simulated via controlled irrigation cessation during critical growth stages to mimic terminal drought, while a parallel well-watered treatment served as a reference. Biochar materials used were derived from a fast-growing agricultural feedstock, characterized by high porosity, alkaline pH, and stable mineral contents, with quantification of polycyclic aromatic hydrocarbons and heavy metals below safety thresholds. Results indicated that biochar amendments significantly increased SOC stocks across all sites, with the greatest accumulation observed at 20 t ha-1, corresponding to an average SOC gain of 18–25% over two seasons under drought conditions. Improvements in soil moisture retention by biochar, particularly in the loamy sand and sandy loam soils, reduced evapotranspiration losses and sustained root-zone moisture during terminal drought episodes. Soil pH modestly shifted alkaline with higher biochar rates, enhancing the availability of certain micronutrients (Zn, B) while maintaining buffering capacity. CEC increased proportionally with biochar rate, contributing to higher nutrient holding capacity and reduced leaching losses under water deficit. Crop yield displayed a positive response to biochar, with grain yields increasing by 12–35% at 5–20 t ha-1, with the magnitude depending on site texture and initial soil organic matter. Harvest index improved at intermediate biochar rates, indicating more efficient allocation of assimilates to grain under limited water. WUE improved by 8–22% in biochar treatments, illustrating enhanced biomass production per unit water. A synergy was observed between biochar and soil microbial biomass, evidenced by elevated enzymatic activities (dehydrogenase and phosphatase) and increased mycorrhizal colonization, suggesting a microbial-mediated pathway for SOC stabilization and nutrient cycling under drought stress. Statistical analyses using mixed models revealed significant interaction effects between biochar rate, soil texture, and irrigation regime on SOC, mineral nitrogen, and yield components (p < 0.05). Sensitivity analyses showed that the SOC sequestration potential was robust to varying climate scenarios, while yield gains were more contingent on soil moisture retention and nutrient availability. The study demonstrates that biochar amendments can simultaneously promote SOC sequestration and stabilize crop yield in semi-arid systems facing drought, primarily through improvements in soil structure, water-holding capacity, nutrient retention, and microbially mediated soil processes. The findings provide actionable guidance for optimizing biochar application rates by soil texture to maximize carbon sequestration and agricultural resilience under water-limited conditions.

Project Overview

What This Project Is About

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A plain-language overview of how adding biochar to soil might change soil health and crop yields when rainfall is limited in a dry region, and how this could help farms store carbon in the soil over time.

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The Problem It Addresses

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Soils in semi-arid areas often lose fertility and produce lower yields during drought. Biochar is a charcoal-like material added to soil that can help hold water and nutrients, potentially boosting crops and increasing soil carbon storage. The project investigates whether biochar actually improves yield and soil carbon under drought, and how big the effect might be.

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Objectives of the Project

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1. Assess how biochar affects crop yield under drought conditions.
2. Measure changes in soil organic carbon when biochar is added.
3. Evaluate water-holding capacity and soil moisture dynamics with biochar.
4. Compare different biochar types or rates to find the most effective option.

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What You Will Do Step by Step

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1. Review basics of soil health and drought impacts on crops.
2. Set up simple field or greenhouse trials with biochar treatments and controls.
3. Collect soil samples to measure organic carbon and moisture regularly.
4. Grow a test crop and record yields under varying rainfall or irrigation.
5. Analyze data to see if biochar improved soil carbon and yield compared with controls.
6. Discuss practical implications for farmers and recommendations for use.

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Expected Outcome

Evidence on whether biochar can enhance soil carbon storage and crop yield during drought, plus practical guidelines on when and how to use biochar in semi-arid farms.