Philippine Journal of Science
152 (1): 253-267, February 2023
ISSN 0031 – 7683
Date Received: 01 Jun 2022
Influence of Bamboo Biochar, Arbuscular Mycorrhizal
Fungi, and Nitrogen-fixing Bacteria as Soil Amendments
on Cacao (Theobroma cacao L.) Planted in Acidic Soil
Joshua G. Jomao-as1,2*, Noel S. Sabino3, Bernadette C. Mendoza3, Nelly S. Aggangan4
1Graduate School, University of the Philippines Los Baños, Laguna, Philippines
2Department of Science and Technology–Science Education Institute (DOST-SEI),
Bicutan, Taguig City, Philippines
3Microbiology Division, Institute of Biological Sciences, College of Arts and Sciences,
University of the Philippines Los Baños, Laguna, Philippines
4National Institute of Molecular Biology and Biotechnology,
University of the Philippines Los Baños, Laguna, Philippines
*Corresponding author: jgjomaoas@up.edu.ph
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Jomao-as J et al. 2024. Influence of Bamboo Biochar, Arbuscular Mycorrhizal Fungi, and Nitrogen-fixing Bacteria
as Soil Amendments on Cacao (Theobroma cacao L.) Planted in Acidic Soil. Philipp J Sci 152(1): 253–267.
https://doi.org/10.56899/152.01.19
ABSTRACT
This study determined the influence of varying soil amendments containing bamboo biochar (BB) with or without biofertilizers on the populations of arbuscular mycorrhizal fungi (AMF) and nitrogen-fixing bacteria (NFB), on plant growth, and soil parameters in acidic soil under nursery conditions. Cacao var. UF18 were sown in polypropylene bags filled with a 200-g ovensterilized soil-sand mixture. After a month, cacao seedlings were transferred to a mixture of unsterilized acidic soil (4.65 pH) and vermicompost (3:1, w/w) and amended with BB (w/w) at varying concentrations (0, 15, and 30%). Inoculation with available formulated AMF inoculants (AMF1 and AMF2) and NFB, singly and in combination, was also done during this stage by adding the recommended rates directly beneath the roots. The results showed that regardless of biochar concentration and the type of AMF inoculum used, there was a significant decrease in AMF spore count and root colonization when AMF and NFB were combined. Root colonization in cacao by AMF1 or AMF2 showed no significant difference from each other. In general, the amendment of BB could have resulted in better soil properties such as increased pH, nitrogen (N), and phosphorus (P), which provided a condition where microorganisms can optimally grow. However, co-inoculation of AMF and NFB resulted in a decrease in both spore count and root colonization, suggesting possible adverse interaction between the microorganisms. Co-amendment of 15% BB and biofertilizer (NFB or AMF1 alone) resulted in heavier (140 and 130 g plant–1) plant biomass compared with single inoculation of BB or biofertilizer (50–90 g plant–1). Moreover, the highest N uptake (2257 mg plant–1) was observed in cacao plants inoculated with NFB grown in 15% BB-amended soil. Cacao seedlings inoculated with NFB and AMF1 and amended with 15% BB soil resulted in the highest uptake of P (537 and 539 mg plant–1, respectively). The results clearly showed the beneficial effects of combining biofertilizer and BB at 15% concentration as compared to 0 and 30%. It is recommended that the same treatments be done in a field study to verify the results obtained in the nursery experiments.