Use of coal ash- and lignite-enriched compost to improve soil biological properties and reduce pineapple disease in Ultisols of Central Lampung

Abstract

Ultisols used for pineapple cultivation are classified as suboptimal lands because of their low soil fertility. Application of compost enriched with other soil ameliorants, such as coal ash in the form of fly ash, bottom ash (FABA), and lignite, can be a good alternative to improve soil properties, including increasing the soil microbial and fauna populations, which play an important role in improving soil fertility and reducing the incidence of pineapple disease. The purpose of this study was to investigate the effects of FABA- and lignite-enriched compost on microbial and earthworm populations and the incidence of pineapple disease. FABA- and lignite-enriched compost at a dose of 50 tons/ha was applied using a spread-and-row technique in the pineapple plantation area in Central Lampung. The parameters observed included the microbial population (Pseudomonas, Bacillus, Actinomycetes, Trichoderma), functional microbial populations (nitrogen-fixing bacteria, phosphate-solubilizing microbes, siderophore producers), earthworm population, and incidence of pineapple diseases (marbling, brown spot, cork spot, and pink diseases). Generally, all treatments with FABA- and lignite-enriched compost showed better results than the control for all observed parameters. The treatment of FABA-enriched compost applied with a row technique was the best compared to other treatments because it tended to increase the population of Pseudomonas, Bacillus, Actinomycetes, and nitrogen-fixing bacteria, as well as earthworm abundance and biomass. In addition, in this treatment, there was no incidence of pineapple fruit disease. The abundance of earthworms and soil microbes, especially Pseudomonas was one of the factors which can create a healthier soil ecosystem to suppress the incidence of pineapple diseases.