v1.2 (2026-06-11) · Silva, J.A., and R. Uchida (eds.). 2000. Plant Nutrient Management in Hawaii's Soils, Approaches for Tropical and Subtropical Agriculture. College of Tropical Agriculture and Human Resources (CTAHR), University of Hawaii at Manoa. Chapters 2 (Hue/Uchida/Ho — sampling & lab methods), 6 (Yost/Tamimi/Silva/Hue/Evensen — how recommendations are made), 7 (Yost/Uchida — interpretation, Tables 7-1 / 7-2 / 7-3), 8 (Silva — calibration methodology), 9 (Hue/Ikawa/Huang — external P requirement, Table 9-1). Adequacy levels from Tamimi, Silva, Yost, Hue (1997), CTAHR AS-3 'Adequate Nutrient Levels in Soils and Plants in Hawaii'. ADSC routine P method changed from Rapid Chemical Method to Modified Truog (Ayres & Hagihara 1952) for acid soils; Olsen for soils pH > 7.0. NEWEST CTAHR references (verified 2026-06-11): Hue, N.V. & R.L. Fox. 2010. 'Predicting Plant Phosphorus Requirements for Hawaii Soils using a Combination of P Sorption Isotherms and Chemical Extraction Methods.' Commun. Soil Sci. Plant Anal. 41(2):133-143 (CTAHR / UH-Manoa, peer-reviewed; supplies the post-2000 Mehlich-3/Olsen/Modified-Truog ↔ soil-solution-P conversion + P buffer coefficients). Reppun, Silva, Wong & Deenik. SCM-33 'A Soil Phosphorus Primer for Hawaiian Soils' (CTAHR Soil & Crop Management, ©2011, reprinted Aug 2017; qualitative method primer — reaffirms the Fox-Kamprath framework, cites Hue & Fox 2010, no numeric rate table).
State extension method. Zone Forge computes this source's supported nutrient rates in-app and cites the published method. Its published lime method is computed in-app too.
Yes — Zone Forge's calculators are free and need no signup. This page shows the states and crops Hawaii — UH-Manoa CTAHR Agricultural Diagnostic Service Center covers so you can verify the source behind your recommendation.
Browse the full Coverage Explorer — every state, crop and source — or see the science →