Effect of biochar amendments on soil salinity mitigation and crop yield in coastal saline soils: a field trial using different feedstocks and application rates

Project Abstract

This study investigates the efficacy of biochar amendments in mitigating soil salinity and enhancing crop yield in coastal saline soils through a field-based trial employing diverse feedstocks and application rates. The experimental design followed a split-plot arrangement with three biochar feedstocks (rice husk, coconut shell, and cassava peel) and four application rates (0, 5, 10, and 20 t ha-1), replicated across four saline-prone field sites to capture spatial variability. Baseline soil properties were characterized for salinity (ECe), pH, cation exchange capacity, organic matter, and nutrient status prior to amendment, with periodic soil sampling conducted at 0, 3, 6, and 12 months post-treatment. A salt-tolerant maize variety was planted to quantify agronomic performance, while parallel assays assessed germination, biomass accumulation, root morphology, and chlorophyll content to elucidate physiological responses to salinity stress and biochar-mediated amelioration. Results indicate that biochar amendments significantly reduced soil electrical conductivity (ECe) and improved soil physical structure, evidenced by decreased bulk density and increased total porosity, particularly at intermediate application rates (10 t ha-1) across all feedstocks. The liming effect of ash-rich biochar marginally increased soil pH, contributing to enhanced nutrient availability, notably potassium, calcium, and magnesium, with differential responses linked to feedstock chemistry. Plant growth metrics showed marked improvements in surviving stands under saline conditions shoot height, leaf area, and biomass were highest at 10 t ha-1 for rice husk biochar, while cassava peel biochar performed best at 5 t ha-1, suggesting feedstock-specific interactions with soil moisture retention and salt alleviation. Yield components—ears per plant, kernel weight, and overall grain yield—revealed a consistent yield gain up to 25–38% relative to control plots, with the magnitude of response modulated by biochar type and application rate. Soil microbial analyses demonstrated enhanced microbial biomass and activity in biochar-amended plots, correlating with improved nutrient cycling and organic carbon stabilization. Hydraulic conductivity measurements suggested moderated leaching losses in amended soils, likely contributing to greater water use efficiency under cyclic irrigation and drought stress episodes typical of coastal environments. Multivariate analyses identified ECe reduction, improved cation exchange capacity, and increased soil organic carbon as primary drivers of yield enhancement, with feedstock-dependent effects on pore structure and moisture retention amplifying salinity tolerance. Economic evaluation indicated favorable cost-benefit trends for 10 t ha-1 applications in rice husk and coconut shell biochars, considering input costs, yield gains, and potential long-term soil quality improvements. The study concludes that biochar amendments can effectively mitigate soil salinity and boost crop yield in coastal saline soils, with optimal performance contingent on feedstock selection and application rate. The findings support site-specific biochar management as a viable component of integrated saline soil restoration strategies, offering actionable guidance for farmers and policymakers aiming to enhance agricultural productivity in marginal coastal zones.

Project Overview

What This Project Is About

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This project looks at how adding biochar to coastal soils might help reduce salt stress for plants and improve crop yields. It compares different biochar types made from various materials and tests different amounts to see what works best in salty environments.

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The Problem It Addresses

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Coastal soils often have high salt levels that stress crops, lowering growth and yield. Biochar is a charcoal-like material that can improve soil properties, but it’s not clear which biochars or application rates work best in salty soils. The study aims to fill this gap with practical guidance for farmers and land managers.

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Objectives of the Project

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1. Identify how different biochar types affect soil salinity and plant growth.
2. Compare crops’ yield responses to varying biochar application rates.
3. Explain how biochar changes soil properties such as water retention and nutrient availability in saline conditions.
4. Provide recommendations for field use in coastal farming.

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What You Will Do Step by Step

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1. Review basic concepts about soil salinity and biochar. 2. Collect soil and plant data from field plots with different biochars and rates. 3. Measure soil electrical conductivity, moisture, and nutrients. 4. Record crop growth stages and yields. 5. Analyze data to compare treatments. 6. Interpret results and draft practical guidelines.

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Expected Outcome

Expect to identify a biochar type and rate that most effectively reduces soil salinity effects and boosts crop yield, along with practical soil management tips for coastal farms. The findings aim to guide farmers and policymakers on using biochar as a soil amendment in salty environments.