BACKGROUND AND OBJECTIVES: Excessive reliance on inorganic nitrogen–phosphorus–potassium fertilizers in shallot (Allium cepa var. aggregatum) production can degrade soil quality, increase nutrient losses, and reduce smallholder profitability. This study assessed the potential of locally sourced organic nutrients, in conjunction with a microbial biofertilizer, to maintain shallot yield and enhance soil characteristics in tropical environmentsMETHODS: An experimental design based on a randomized complete block with six treatments and four replicates; each replicate consists of ten plants. Treatments compared one hundred percent mineral fertilizer; fifty percent mineral fertilizer combined with poultry manure; fifty percent mineral fertilizer combined with poultry manure plus the Biosoltamax microbial biofertilizer. In addition, fifty percent mineral fertilizer combined with sheep manure plus the Biosoltamax microbial biofertilizer black soldier fly frass compost. Followed by fifty percent mineral fertilizer combined with black soldier fly frass compost (locally named ‘Kasgot’) and the commercial microbial biofertilizer Biosoltamax; and an additional treatment as specified in the methods. An evaluation was conducted on plant growth and yield parameters, soil chemical properties, urease activity, and the use of scanning electron microscopy with energy dispersive spectroscopy. Statistical analyses included analysis of variance and mean separation at a probability less than 0.05.FINDINGS: The treatment combining fifty percent mineral fertilizer, black soldier fly frass compost and Biosoltamax produced strong vegetative growth (maximum plant height 48.95 centimeters; maximum fresh leaf biomass 84.08 grams per plant) and high bulb productivity (mean fresh bulb weight 49.75 grams per bulb; mean 5.25 bulbs per plant, equivalent to about 261.2 grams fresh bulb mass per plant). Under integrated organic and reduced mineral regimes, soil organic carbon increased from 1.35 percent to 1.59 percent, and total nitrogen rose from 0.14 percent to 0.175 percent; furthermore, there was also an increase in urease activity. Energy dispersive spectroscopy showed that carbon and oxygen dominated the soil particle composition (carbon: 45–55 percent; oxygen: 36–42 percent), consistent with enriched organic-matter inputs.CONCLUSION: Using poultry manure and earthworm compost from black soldier fly frass along with a microbial biofertilizer and decreasing mineral fertilizer application, can preserve shallot yield and simultaneously improve soil organic carbon, total nitrogen, and soil properties. This combined approach supports healthier soil and offers an environmentally safer alternative to full mineral fertilizer use.
Nurawan et al. (Thu,) studied this question.
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