the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 08 Aug 2025
Effect of trachyte and basalt rock powders on maize (Zea mays L.) growth and yield on Fluvisols in Cameroon’s Sudano-Sahelian zone (Central Africa)
Abstract. The Sudano-Sahelian zone of Cameroon, characterized by a low annual rainfall, faces challenges in soil fertility preservation due to agricultural intensification and unsustainable practices. This study aims to evaluate the effect of trachyte and basalt powders inputs on soil and maize yield in Guiring experimental farm. Fieldwork involved collecting and describing samples of trachyte, basalt, and soil and setting up the experimental design. In the laboratory, the ground rock samples underwent geochemical analysis, and the soil samples were analysed for their mineralogical and physicochemical properties. The experiment followed a completely randomized block design with six treatments (T0, T1, T2, T3, T4, and T5) and four replications. Growth and yield parameters of maize, include germination rate, plant height, number of leaves per plant, stem diameter, ear length, ear diameter, ear weight, 100-grain weight, and grain yield (kg ha-1). The soil consists of kaolinite, smectite, sepiolite, and quartz. Its texture is dominated by sand fraction, with a neutral pH (7.0). The organic matter (2.6±0.67 %) and total nitrogen contents (0.1±0.0 %) are relatively low. The concentrations of potassium, magnesium, sodium, and calcium are 0.2±0.1 cmolc kg-1, 2.5±1.6 cmolc kg-1, 0.3±0.2 cmolc kg-1, and 3.9±1.5 cmolc kg-1, respectively. The cation exchange capacity is moderate to high (22.1±2.5 cmolc kg-1), while the available phosphorus content is high (19±7.0 mg kg-1). This soil is classified as Ochric Dystric Fluvisols according to the WRB. These soil characteristics are moderately suitable for maize cultivation. Fertilization trials showed a significant improvement in maize growth and yield, within plots treated with basalt powder yielding higher (2558.6 kg ha-1 and 2931.2 kg ha-1) than those treated with trachyte powder (2362.9 kg ha-1 and 2763.9 kg ha-1) and the control plots (645.8 kg ha-1). Plots treated with NPK fertilizer recorded the highest yield (3164.5 kg ha-1). Although the treatment with conventional fertiliser resulted in a relative higher yield, the advantage of using rock powders lies in their environmental benefits, long-term effectiveness, and more affordable cost.
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Status: open (until 10 Nov 2025)
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RC1: 'Comment on egusphere-2025-3474', Diego Tassinari, 23 Sep 2025
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AC2: 'Reply on RC1', Désiré Tsozué, 15 Oct 2025
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The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-3474/egusphere-2025-3474-AC2-supplement.pdf
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AC2: 'Reply on RC1', Désiré Tsozué, 15 Oct 2025
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CC1: 'Comment on egusphere-2025-3474', Eder Martins, 06 Oct 2025
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Following the review, the manuscript showed considerable improvement; however, a few minor adjustments to phrasing and conceptual clarity are still required.
The text uses both 'fertiliser' and 'fertilizer'. Please choose one.
The names of chemical elements must be in lowercase letters.
Table 4 - Change "Basalte" to "Basalt"
Suggestions
Lines 29 and 30: Change the original sentence "Although the treatment with conventional fertiliser resulted in a relative higher yield, the advantage of using rock powders lies in their environmental benefits, long-term effectiveness, and more affordable cost" for improved version "Although treatments with conventional fertilizers resulted in comparatively higher yields, rock powders offer significant advantages by facilitating region-specific strategies that deliver environmental benefits, durable effectiveness, and improved affordability.
Lines 66 and 67: Change the original sentence "In Cameroon, in particular, several studies have demonstrated the effectiveness of these powders" for improved version "Multiple studies conducted in Cameroon have demonstrated the effectiveness of these rock powders"
Lines 79 and 80: Change the original sentence "As the minerals constituting rocks dissolve, the released chemical elements become available to plants" for improved version "The chemical elements released during the weathering of rock minerals become available to plants"
Line 481: It is better to use "bioweathering" instead of "biogeochemical".
Lines 521 and 522: Change the original sentence "Trachyte powder, with relatively high concentrations of K₂O and Na₂O, promotes plant growth, particularly potassium, which is essential for photosynthesis and water regulation." for improved version "Trachyte powder, with relatively high concentrations of K₂O and Na₂O, promotes plant growth, particularly potassium, which is essential for photosynthesis and water regulation."
Lines 557 and 558: Change the original sentence "The soils in Guiring, dominated by a high sand content (62-82%) and low clay (13-23%) and silt (5-15%) contents." for improved version "The soils in Guiring are dominated by a high sand content (62–82%) and have low clay (13–23%) and silt (5–15%) contents."
Citation: https://doi.org/10.5194/egusphere-2025-3474-CC1 -
AC1: 'Reply on CC1', Désiré Tsozué, 15 Oct 2025
reply
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-3474/egusphere-2025-3474-AC1-supplement.pdf
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AC1: 'Reply on CC1', Désiré Tsozué, 15 Oct 2025
reply
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RC2: 'Comment on egusphere-2025-3474', Anonymous Referee #2, 11 Oct 2025
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The manuscript presents an interesting and relevant study exploring alternative sources of fertilization for maize production in the Sudano-Sahelian zone of Cameroon (Central Africa). The work provides rich pedological, mineralogical, and agronomic information and applies a detailed methodology. The results are well organized and clearly presented.
However, the manuscript requires several major revisions to improve scientific rigor, structure, and coherence between the pedological analysis and the field experiment.
Major Revisions
- Title and Abstract
- The title and abstract should be revised to accurately reflect the main findings of the study. As currently written, they partially present the experimental results, lacking emphasis on pedological information and crop suitability.
- Introduction
- The introduction should be restructured to better reflect the reality of soil fertility management in Africa, where fertilizer use remains low and nutrient depletion is the dominant challenge. To structure the introduction around “intensive agriculture” does not align with the general conditions of sub-Saharan smallholder systems.
- Integration of Pedological Information / crop suitability
- The manuscript includes a detailed pedological study and soil and crop suitability assessment, but this information was not integrated into the experimental design or discussion (example: treatment based on soil organic amendment to improve the water retention in sandy soils). The authors should link the soil information generated in the first section to treatment responses, explaining how these factors may have influenced maize growth and yield.
- Section on Nutrient Release Kinetics
- The section discussing the kinetics of nutrient release from trachyte and basalt powders lacks supporting experimental data. Since no direct measurements of nutrient release dynamics or plant uptake were conducted, this section should be removed or significantly shortened to avoid overinterpretation.
Specific Comments
- Lines 20–25: Improve this section by summarizing the dominant soil clay minerals and overall texture and remove overly descriptive details that are not directly relevant to the main results.
- Lines 35–40: The general statement does not accurately reflect the current reality of African agriculture. Please rephrase to reflect context-specific challenges, such as low fertilizer use, limited access to inputs, political issues, logistics constraints, and soil nutrient depletion.
- Lines 45–50: Clarify the conceptual difference between soil health and soil quality.
- Lines 50–55: The statement suggesting that intensive agriculture is a major problem in Africa is misleading. In most African systems, the challenge is low agricultural intensification rather than overuse of inputs.
- Line 121: Remove the duplicated reference to “(Table 1)”.
- Line 135: Avoid using abbreviations such as “IRAD” at their first occurrence; write the full name before introducing the acronym.
- Line 290: Add in Table 4, the international regulatory limits for trace elements in soil amendments and fertilizers, for proper environmental assessment.
- Line 327: In Table 6, avoid introducing abbreviations such as “TEB” before defining them.
- Line 480: The section titled “4.3 Kinetics of nutrient element release from trachyte and basalt powders” is overstated. The experimental design does not allow evaluation of release kinetics, plant uptake, or nutrient dynamics. This section should be removed.
- Line 508: The suggestion to use amendments based on clay materials is not cost-effective for smallholder farmers. Given the applied nature of the research, the socio-economic feasibility of proposed solutions should be considered in the recommendations.
Citation: https://doi.org/10.5194/egusphere-2025-3474-RC2
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General comments
The manuscript presents a multidisciplinary study that seems to fall well within the scope of the journal, covering fields such as petrography, land evaluation, pedology, soil mineralogy, fertility and a field trial with soil amendments (rock powders or remineralizers). In addition to the very comprehensive characterization of the rocks and the soil, the field trial presents a practical and direct application of this initial assessment, highlighting the specific conditions under which the crops positive response was observed. Although simplistic, with modest sources and doses of fertilizers and remineralizers, the field trial must be evaluated also considering the low availability of published data from the studied region, the amount of work needed to grind dozens of kilograms of rock and the significant responses obtained. In addition, the practical applications of the results for this region and elsewhere are very significant, as they deal with fertilizer shortage and food security. What may seem as major setbacks of the study are the lack of plant nutrient contents to show how nutrient uptake responded to the treatments and the field trial restricted to a single crop cycle. Regarding the latter, it must be pointed out that significant differences in yield were already perceived in this first cycle.
Specific comments
Treatment application is not clear enough. It is important to understand how the rock powder was applied, with broadcasted in the entire plot or locally applied and whether it was incorporated or not by any tillage practice.
Yield results could be presented also as relative yield, especially in the discussion, conclusion and abstract, because it may be more directly referred by other studies. For example, for NPK + urea as 100% relative yield, basalt + urea reached 92.6% and trachyte + urea reached 87.3% of the maximum yield, whereas the remineralizers alone resulted in relative yields of 80.8% and 74.7% for basalt and trachyte respectively.
Technical corrections
Provided in the appended PDF document.