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.

Pressurized hot water and DTPA-Sorbitol are two relatively new soil boron (B) extraction methods with potential to replace the cumbersome hot water extraction. The objective of this research is to produce data in support of acceptance or rejection of these two alternative B extractions. The three soil tests were used to extract B from samples of calcareous sand and silt loam and limed, loamy fine sand treated with 10 levels of B and incubated for 7 and 28 d. As B application increased so did extractable B with each extraction method. High correlations (r of 0.977 to 0.999) were observed between extractable B and rate of B application with all three methods. Hot water generally extracted the least and pressurized hot water the most B regardless of soil type, rate of application or duration of incubation. Greenhouse and field experiments were conducted on one limed acid and two alkaline soils naturally low in B to test alfalfa response to B fertilizer. Values from the three soil extraction methods were correlated to yield, B tissue concentration and total B removal of alfalfa. In greenhouse studies with varying levels of soil applied B, highly significant relationships exist between extractable soil B and both tissue B concentration and total B removal. Correlations between yield and extractable soil B were impossible to obtain because of a lack of alfalfa yield responses to applied boron. All three methods accurately predict plant B tissue concentrations and total B removal. The field experiment produced a significant positive relationship between total alfalfa yield and extractable B using hot water and pressurized hot water extractions, but not using DTPA-Sorbitol. The results observed in this research support pressurized hot water extraction as the better of the two alternatives to replace hot water extraction in a broad range of soil types.