| 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.
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.