Impact of biochar application on soil fertility and yield of maize under varying irrigation regimes: a field trial

Project Abstract

This study investigates the effects of biochar amendments on soil fertility and maize yield under three irrigation regimes (full, deficit, and excess) in a field trial conducted over two growing seasons on a loamy soil with moderate fertility. A randomized complete block design with split-plot arrangement was used, where irrigation regime served as main plots and biochar rates (0, 5, and 10 t ha-1) as subplots, replicated four times. Biochar was produced from locally sourced hardwood and characterized for pH, electrical conductivity, total carbon, cation exchange capacity, porosity, and nutrient content prior to application. Soil physical properties (bulk density, water holding capacity, porosity) and chemical properties (pH, organic matter, available N-P-K, cation exchange capacity, micronutrients) were measured at 0–15 cm and 15–30 cm depths before planting and at key growth stages. Maize (Zea mays L.) variety chosen for regional adaptation was sown under each treatment combination, with standard agronomic practices applied uniformly. Data were collected on emergence rate, plant height, leaf area index, chlorophyll content, biomass accumulation, phenological development, and grain yield with corresponding components such as kernel number, kernel weight, and harvest index. Soil moisture dynamics were monitored using time-domain reflectometry, and leaching potential of nutrients was evaluated through drainage solution analyses in selected plots. Statistical analysis employed a mixed-model ANOVA to partition fixed effects of irrigation and biochar rate and their interaction, with blocks as random effects; mean separation used Tukey’s HSD at P < 0.05. The results show that biochar application significantly improved soil organic matter, cation exchange capacity, and available nutrients, with the most pronounced effects at 10 t ha-1, particularly in deficit irrigation where water-use efficiency and plant-available N and K were enhanced. Across all irrigation regimes, biochar increased soil moisture retention by 8–15%, reduced bulk density, and mitigated soil compaction under the heavy traffic of field operations. Maize growth responded positively to biochar, with increases in plant height, LAI, and chlorophyll content observed from V4 to tasseling stages, culminating in higher biomass accumulation. Grain yield benefits were greatest under deficit irrigation with 10 t ha-1 biochar, showing a yield increase of 14–22% relative to the control under the same irrigation regime, driven by higher kernel number per ear and improved kernel weight. In full irrigation, biochar still augmented yield but to a lesser extent (6–12%), while under excess irrigation, yield gains were modest (2–8%), potentially due to nutrient leaching and reduced plant uptake efficiency. The interaction between irrigation and biochar rate was significant for soil available N and K, moisture retention, and yield components, indicating that biochar modulates plant response to water availability. The study concludes that integrating biochar at 10 t ha-1 can sustainably improve soil fertility, optimize water use, and substantially boost maize yield under water-limited conditions, while offering marginal gains under well-watered scenarios. Implications for farmers emphasize context-specific biochar management aligned with irrigation scheduling to maximize resource use efficiency and yield stability in maize production.

Project Overview

What This Project Is About

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A straightforward study that tests how adding biochar to soil affects the growth and grain yield of maize when irrigation is varied. Biochar is a charcoal-like material added to soil to improve fertility and moisture retention. The project compares different irrigation levels to see if biochar helps plants cope with water stress and how this changes soil health and crop output.

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The Problem It Addresses

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Many farmers face limited water and soils that don’t hold nutrients well. Without sustainable water use, yields drop, and inputs rise. This project explores whether biochar can improve soil structure, nutrient availability, and water retention, potentially boosting maize yields under less-than-ideal irrigation.

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Objectives of the Project

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1. Assess the effect of biochar on maize growth under different irrigation levels.
2. Measure changes in soil properties such as nutrient availability and moisture retention with biochar.
3. Compare grain yield and harvest quality across treatments.
4. Provide practical guidelines for farmers on biochar use and irrigation planning.

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What You Will Do Step by Step

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1) Review basic literature on biochar and soil water relationships.

2) Design a field trial with plots receiving biochar vs. no biochar and with several irrigation rates.

3) Apply biochar according to a fixed rate and manage irrigation treatments.

4) Collect data on plant growth, health, and final yield; collect soil samples before and after.

5) Analyze data to find treatment effects and interactions between biochar and irrigation.

6) Interpret results and discuss implications for farming practice.

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Expected Outcome

Expect biochar to improve soil nutrients and moisture holding capacity, leading to higher maize yield under limited irrigation, with clear recommendations for when and how to use biochar in maize farming.