Soil analysis for small acreage farms in developing countries is often inconvenient and prohibitively expensive using current procedures, yet the information gained from these soil tests could have economical and environmental benefits. The pressurized hot-water (PHW) extraction coupled with colorimetric or turbidimetric analyses shows promise as an alternative to current procedures. Accepted methods of colorimetric analysis for NO3-N and P exist but an alternative method to atomic absorption spectrometry for K analysis is needed. Of the many possible methods to quantify K, tests performed in the Brigham Young University (BYU) laboratory found sodium tetraphenylborate to be unsatisfactory and sodium cobaltinitrite to be simple, inexpensive and consistent. Test results on 38 arid-zone soils from the Western United States encourage adoption of sodium cobaltinitrite as an acceptable procedure for K quantification in conjunction with PHW extraction [r2 of 0.90 compared to atomic absorption (AA) analysis and r2 of 0.67 compared to values extracted with ammonium acetate and measured with AA]. Two hundred twenty-eight soils varying widely in soil parameters from different areas of Guatemala and Morocco were analyzed for NO3-N, P and K using standard methods (water-CTA, Olsen-molybdic acid and ammonium acetate-atomic absorption, respectively) and correlated to values obtained from the PHW extraction coupled with colorimetric or turbidimetric analytical procedures at BYU. The correlations between the values for these tests were good (r2 of 0.96, 0.71 and 0.52 for NO3-N, P, and K; respectively). Soils from each country were simultaneously analyzed for NO3-N and P in laboratories in Guatemala and Morocco and these results correlated with those from BYU. Correlations between BYU values and those from other laboratories gave generally positive results with the Guatemala laboratory showing overall closer correlation with BYU values than data from the Morocco laboratory. The results suggest that the PHW extraction and accompanying simplified analyses present a viable, less expensive alternative to current soil nutrient extraction and analysis procedures for the range of soils tested from Morocco and Guatemala.



College and Department

Life Sciences; Plant and Wildlife Sciences



Date Submitted


Document Type





nitrate, phosphorus, potassium, PHW, analysis, soil extraction