Effect of biochar-amended compost on soil health, nutrient availability, and maize yield under varying irrigation regimes in a Loamy Sand soil.

Project Abstract

This study evaluates the effects of integrating biochar into compost on soil health indicators, nutrient availability, and maize (Zea mays L.) yield under contrasting irrigation regimes in a Loamy Sand soil. The experimental design consists of a factorial arrangement with biochar-amended compost (0, 5, and 10 t ha-1 derived from rice husk biochar blended with mature compost) and irrigation regimes representing full irrigation, deficit irrigation at 70% of crop evapotranspiration (ETc), and deficit irrigation at 50% ETc, deployed across a randomized complete block design with three replicates. Baseline soil properties were characterized prior to amendment, including organic matter content, pH, cation exchange capacity, total nitrogen, available phosphorus and potassium, bulk density, and soil moisture retention characteristics. The compost-biochar treatments were incorporated into the top 20 cm of soil and maize was planted and grown to physiological maturity under standard agronomic practices suitable for Loamy Sand soils. Soil health was assessed through a suite of biological, chemical, and physical indicators, including microbial biomass carbon, basal respiration, enzyme activities (dehydrogenase, phosphatase, and urease), aggregate stability, water infiltration rate, and available micronutrients. Nutrient availability was monitored via extractable mineral nutrients (N, P, K, Ca, Mg, and micronutrients) using sequential extractants aligned with standard soil testing protocols, complemented by plant tissue analysis at key growth stages to track nutrient uptake dynamics. Maize productivity was evaluated through grain yield, aboveground biomass, harvest index, and phenological development. Preliminary results indicate that biochar-amended compost enhances soil organic carbon and cation exchange capacity, leading to improved nutrient retention and slower mineralization rates that align with steady nutrient supply under both full and moderate irrigation. Deficit irrigation interacts with amendment level to influence soil moisture dynamics and microbial activity, with the 5 t ha-1 biochar-compost treatment under 70% ETc showing a favorable balance between water use efficiency and nutrient availability, reflected in higher grain yield and harvest index relative to the control and the 10 t ha-1 rate, which, at extreme deficit, tended to immobilize certain micronutrients and reduce yield potential. Biochar presence also mitigates soil bulk density increase, enhances aggregate stability, and improves infiltration under all irrigation regimes, contributing to healthier rhizospheric conditions and more consistent root exploration. The study employs mixed-model ANOVA to discern main effects and interactions between biochar-amended compost and irrigation regimes, followed by regression and response surface analyses to identify optimal amendment rate and irrigation combination. The anticipated outcome is a refined understanding of how biochar-amended compost modulates soil physical structure, nutrient cycling, and water availability to sustain maize yield under water-limited conditions in Loamy Sand soils. The research aims to provide agronomic guidelines for farmers on optimizing compost-biochar applications and irrigation scheduling to maximize soil health and crop productivity while conserving water resources.

Project Overview

What This Project Is About

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A simple study to see how adding biochar to compost affects soil health, the availability of nutrients to plants, and the yield of maize, especially when irrigation is varied. Biochar is charcoal added to soil to improve water and nutrient retention. Compost is decomposed organic matter that provides nutrients. Loamy Sand soil is a mix that drains quickly; the project tests modifications to soil performance under different watering levels.

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The Problem It Addresses

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Soil in some areas loses nutrients and holds water poorly, especially under limited or excessive irrigation. This can reduce crop yields. The project investigates whether biochar-amended compost can improve nutrient supply and soil health, leading to better maize yields across irrigation regimes.

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Objectives of the Project

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1. Assess how biochar-amended compost changes soil health indicators (pH, organic matter, microbial activity).
2. Evaluate nutrient availability for maize (nitrogen, phosphorus, potassium) under different irrigation levels.
3. Measure maize yield and above-ground biomass under the treatments.
4. Identify the irrigation regime that works best with biochar-amended compost in Loamy Sand soil.

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What You Will Do Step by Step

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1. Review literature on biochar, compost, and soil-water interactions.
2. Prepare soil plots with control, compost, biochar, and biochar-amended compost treatments.
3. Apply irrigation schedules representing low, medium, and high water regimes.
4. Monitor soil health indicators and nutrient levels at set intervals.
5. Grow maize and record germination, growth, and final yield.
6. Analyze data to compare treatments and irrigation effects.
7. Discuss practical implications for farmers in similar soils.

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Expected Outcome

Expect improved soil health and higher nutrient availability in biochar-amended treatments, with increased maize yield under specific irrigation levels. The study should offer practical guidance on using biochar-amended compost to stabilize yields in Loamy Sand soils with varying water supply.