International Journal of Plant & Soil Science

Aims: To optimize the dose of three ameliorants (biochar, lime, and compost) and their interactions on the availability of macronutrient P.

Study Design: This research was a laboratory incubation study using soil samples from the newly opened rice fields.

Place and Duration of Study: Paddy field of Ray 7, Balandean Village, Alalak District, Barito Kuala Regency, South Kalimantan Province from May to November 2021.

Methodology: The study used factorial design with the treatments of 1) Biochar, with levels of 0, 10, and 20 t ha^-1, 2) Lime, with levels of 0, 2, and 4 t ha^-1, 3) Compost with levels of 0, 5, and         10 t ha^-1. All were arranged in Completely Randomized Design with three replications. The experimental units were 300 g of soil sample in 81 of 10 cm plastic pots. They immersed up to 2 cm water and incubated to imitated field conditions for three months and then analyzed for the parameters.

Results: Biochar and lime increased available-P quadratically and linearly following orthogonal polynomial analyses. Their interaction was highly significant in increasing available-P. The doses for both could be increased for the maximum availability of P.

Conclusion: Biochar increased P availability with the tendency of increasing beyond the dose of the treatment. The main treatment of compost was not as good as biochar. However, when applied together with biochar and lime, compost affected the solubility of P. However, to increase P availability, the combination of the ameliorants showed a good synergism.