Organic Matter Clogging Results in Undeveloped Hardpan and Soil Mineral Leakage in the Rice Terraces in the Philippine Cordilleras

A critical threat to the UNESCO-listed Rice Terraces of the Philippine Cordilleras—flooded paddies at risk of collapse due to excessive water infiltration—has been linked to organic matter clogging rather than the intended hardpan formation. Research reveals that high organic matter content, which suppresses water drainage, leads to reductive soil conditions and mineral leaching (phosphorus, potassium, calcium, manganese). Field surveys and soil analysis demonstrated that undeveloped hardpans, combined with organic buildup, hinder terrace stability while depleting essential nutrients. Unlike hardpan formation, organic clogging is invisible from the surface, complicating management. The study advocates for pre-planting hard layer checks and post-crop drainage during the rainy season to mitigate risks while sustaining traditional farming practices.

Kurozumi, T., Mori, Y., Somura, H., & O-How, M. (2020). Organic Matter Clogging Results in Undeveloped Hardpan and Soil Mineral Leakage in the Rice Terraces in the Philippine Cordilleras. Water, 12(11), 3158. https://doi.org/10.3390/w12113158