Is there a way to reduce reliance on inorganic fertilizers while still improving crop yields and soil health? A recent study by Mita Sapitri, Mulyati, and IGM Kusnarta, published in the Formosa Journal of Science and Technology (FJST), investigated this very question. Their research explored how different soaking durations of coconut shell biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More in compost tea, combined with varying doses of Phonska Plus fertilizer, affect the growth, yield, and soil fertility of shallots. The findings suggest a promising and sustainable approach to agriculture.

The experiment was a factorial completely randomized design conducted in a greenhouse setting. Researchers tested four soaking durations for the biochar—0, 12, 24, and 36 hours—and four doses of Phonska Plus fertilizer, ranging from 100 to 400 kg/ha. The shallot plants, a high-value vegetable crop in Indonesia, were monitored throughout their growth cycle, with soil samples taken both before planting and after harvest to analyze their chemical and biological properties.

The results were compelling. Soaking duration was a critical factor, significantly improving plant growth, yield components, and key soil parameters like pHpH is a measure of how acidic or alkaline a substance is. A pH of 7 is neutral, while lower pH values indicate acidity and higher values indicate alkalinity. Biochars are normally alkaline and can influence soil pH, often increasing it, which can be beneficial More, organic carbon, and available nutrients (N, P, K). The study found that soaking biochar for 36 hours yielded the highest wet tuber weight, at 12.6 grams, a significant increase compared to 7.4 grams for the non-soaked biochar treatment. This represents an impressive 70% increase in wet tuber weight simply by extending the biochar soaking time. The 36-hour soak also produced the highest dry tuber weight (9.0 grams), and the largest tuber diameter (3.8 cm), reinforcing its positive impact on yield. The researchers noted that while soaking biochar for a shorter period (12-24 hours) showed a positive trend, soaking it for too long could potentially disrupt the nutrient balance around the roots, though this was not statistically significant in the number of bulbs.

Similarly, the Phonska Plus fertilizer dosage had a notable impact on plant growth and yield. Increasing the fertilizer dose to 400 kg/ha resulted in the highest plant height and number of bulbs, showing that adequate nutrient supply is essential for shallot development. However, the researchers also pointed out that previous studies have shown that fertilizer doses above 300 kg/ha may not provide a significant yield increase, as plants can reach a saturation point for nutrient intake. This suggests that combining biochar with a moderate fertilizer dose may be the most efficient strategy. In fact, other research cited in the paper indicated that using soaked biochar can reduce fertilizer needs by up to 25% without sacrificing productivity.

Beyond the direct impact on plant growth and yield, the study also revealed how the treatments affected soil health. The biochar soaking significantly increased the number of fungal colonies in the soil, with the 36-hour soak (B3) yielding the highest count at 31.3×104 CFU/g of soil. This was significantly different from the non-soaked biochar (B0), which had the lowest count at

21.9×104 CFU/g. This increase shows that compost tea enriches the biochar with beneficial microbial populations, while the biochar itself creates a stable environment for these microbes to thrive. In contrast, higher doses of Phonska Plus fertilizer led to a significant decrease in fungal colonies, highlighting a potential negative effect of excessive inorganic fertilizer use on soil biology. The interaction between treatments was also significant for several soil chemical properties. For example, the combination of the highest fertilizer dose (P3) and a 36-hour biochar soak (B3) resulted in the highest available potassium (K) level, showing a synergistic effect.

The findings demonstrate that soaking coconut shell biochar in compost tea is an effective way to improve soil fertility and shallot productivity, offering a sustainable alternative to relying solely on inorganic fertilizers. The 36-hour soaking duration proved particularly effective in boosting yield components and fostering a healthy soil microbial community. This approach can help farmers enhance crop output while mitigating the negative environmental effects of chemical fertilizers, paving the way for more sustainable agricultural practices

Source:Sapitri, M., Mulyati, & Kusnarta, I. G. M. (2025). Effectiveness of Coconut Shell Biochar Soaking Duration and Phonska Plus Dosage (15 15 15) in Increasing Soil Fertility, Growth, and Yield of Shallots. Formosa Journal of Science and Technology (FJST), 4(8), 2413–2432.