Soil analysis for small-scale farms in developing countries is often inconvenient and prohibitively expensive using currently available procedures, yet the information gained from these soil tests could result in economical and environmental benefits. The pressurized hot water (PHW) extraction coupled with colorimetric or turbidimetric analysis shows promise as a viable alternative based on tests done on a limited range of soils. Before this extraction and analysis can be used in developing countries, testing is needed across the range of soils found in these countries. At Brigham Young University (BYU), 228 soils from different areas of Guatemala and Morocco were analyzed for NO 3 -N, phosphorus (P), and potassium (K) using standard methods (water -CTA, Olsen -molybdic acid, and ammonium acetateatomic absorption, respectively). Results were correlated to values obtained from the PHW extraction coupled with colorimetric or turbidimetric analytical procedures. The relationships between the values for these tests were good (r 2 of 0.96, 0.71, and 0.52 for NO 3 -N, P, and K, respectively). Soils from each country were concurrently analyzed for NO 3 -N and P in laboratories in Guatemala and Morocco, and these results were correlated with those from BYU. Positive correlations between BYU values and those from other laboratories were obtained, with the data from the 993 Guatemalan laboratory showing overall closer correlation than the Moroccan laboratory. In an additional study comparing several P extraction methods for Guatemalan soils, relationships between PHW-extracted P and Olsen-, Bray I-, and Mehlich I-extracted P and measured at BYU (r 2 of 0.75, 0.67, and 0.46, respectively) indicate that PHW is a promising alternative P extraction for use even with the highly variable soils of Guatemala. Overall, the data support PHW extraction and accompanying analyses as a less expensive alternative to current soil nutrient extraction and analysis procedures for the soils of Morocco and Guatemala.

Colorimetric or turbidimetric quantification of soil potassium (K) coupled with pressurized hot-water (PHW) extraction could provide an inexpensive alternative to standard methods for small-scale farmers in developing countries. Two of many methods for K analysis, one using sodium tetraphenylborate and the other using sodium cobaltinitrite, were modified for use with PHW extraction and evaluated for the following requirements: readable on the spectrophotometer, minimal equipment requirement, rapid, simple, and comparable in accuracy to proven methods of K analysis. The sodium tetraphenylborate method was unreliable at low K concentrations, did not relate with K extracted using ammonium acetate and analyzed by atomic absorption (AA), required extract filtration and was too expensive in developing countries. Sodium cobaltinitrite was both simple and inexpensive, and results were consistent and reliable. Test results from 38 arid soils from the western United States support the use of sodium cobaltinitrite as an acceptable procedure for K quantification compared to AA analysis (r 2 of 0.90, p , 0.05). When coupled with PHW, K measured using sodium cobaltinitrite was predictably related with ammonium acetate-AA measured K (r 2 of 0.67, p , 0.05).

Soil analysis for small farms in developing countries is often inconvenient and prohibitively expensive, yet the information gained from these soil tests could result in significant benefits. Based on tests done on a limited range of soils, the pressurized hot water (PHW) extraction coupled with colorimetric or turbidimetric analysis is a promising alternative. Before this extraction and analysis can be used in developing countries, testing is needed across the range of soils found in these countries. At Brigham Young University (BYU), 228 soils from Guatemala and Morocco were analyzed for NO 3 -N, phosphorus (P), and potassium (K) using standard methods (water -CTA, Olsen -molybdic acid and ammonium acetateatomic absorption, respectively). Results were correlated to values obtained from the PHW extraction coupled with colorimetric or turbidimetric analytical procedures. The relationships between these tests were good (r 2 values of 0.96, 0.71, and 0.52 for NO 3 -N, P, and K, respectively). In an additional study comparing several P extraction methods for Guatemala soils, relationships between PHW-extractable P and Olsen-, Bray I-, and Mehlich I-extractable P (r 2 values of 0.75, 0.67, and 0.46, respectively) suggest that PHW is a promising P-extraction procedure for use in Guatemala. Overall, PHW extraction and accompanying analyses are a less expensive alternative to current soil nutrient extraction and analysis procedures for the soils of Morocco and Guatemala.