Ann M. Wolf

Comparisons of soil test phosphorus by Olsen, Bray P1, Mehlich I and Mehlich III methods

Abstract A study was undertaken to evaluate the agreement among different university laboratories performing the Olsen, Bray P1, and Mehlich I tests for P on a diverse group of noncalcareous agricultural soils and to develop relationships among the Olsen, Bray P1, Mehlich I, and Mehlich III soil tests. For each test, the results from the individual laboratories were highly correlated (r2 ≥ 0.90) and in almost all instances the slopes of the equations describing the relationships among laboratories approached one, The results indicate that the Olsen, Bray P1 and Mehlich I soil tests may be performed with a high degree of precision when standard soil test procedures are followed. Of the three most commonly performed tests in the U.S. (Olsen, Bray P1, and Mehlich I), the Olsen and Mehlich I tests were the most highly correlated (r2 = 0.87) although the Mehlich I test removed approximately one and one half times more P than did the Olsen test. Bray P1 and Olsen and Mehlich I P were less highly correlated (r2 ...

Colorimetric method for phosphorus measurement in ammonium oxalate soil extracts

Abstract Ammonium oxalate extractable phosphorus represents a potentially useful measure of the P associated with the amorphous iron and aluminum oxides in soils. However, because oxalate complexes molybdate, the colorimetric determination of phosphorus in ammonium oxalate extracts by the traditional molybdenum‐blue procedure is not possible. In this study, a method was developed whereby excessive molybdate was added to the extracts to complex the oxalate and eliminate the interference of oxalate with the formation of the phospho‐moblydate complexes necessary for color development. The method development and recommended procedure for colorimetrically measuring phosphorus in ammonium oxalate soil extracts are described.

Comparison of Shoemaker–McLean–Pratt and Modified Mehlich Buffer Tests for Lime Requirement on Pennsylvania Soils

Abstract The Shoemaker–McLean–Pratt (SMP) buffer test is commonly used in Pennsylvania and throughout the United States to determine the lime requirement (LR) of acid soils. The buffer contains potassium chromate, a carcinogen, and all waste must be collected for disposal in a hazardous waste facility. An alternative to the SMP buffer is the Mehlich buffer. Although the Mehlich buffer contains barium chloride (BaCl2), also a hazardous and regulated compound, calcium chloride (CaCl2) has been shown to be an effective substitute. The goal of this study was to compare the SMP buffer and the modified Mehlich buffer (CaCl2 substituted for BaCl2) for estimating LR on PA soils and to determine if the modified Mehlich buffer could provide an effective alternative to the SMP test. Twenty‐two agriculturally important Pennsylvania soils with pH values ranging from 4.5 to 6.4 were collected, and the actual LR of each soil was determined by incubating soils for 3 months with calcium carbonate. The modified Mehlich buffer was a more accurate predictor of the lime required to raise soils to either pH 6.5 (r2=0.92) or 7.0 (r2=0.87) in comparison to the SMP buffer (r2=0.87 and 0.82, respectively). Comparison of calibration equations for Mehlich buffer versus lime requirement derived in this study were similar to those developed on soils from other states and geographic regions.

Developing an Environmental Manure Test for the Phosphorus Index

Abstract Widespread implementation of the phosphorus (P) index has focused attention on environmental manure tests that can be used to estimate the relative availability of P in manure to runoff water. This article describes the development and use of a water extractable P (WEP) test to assess the capacity of land‐applied manure to enrich P in runoff water. WEP of surface‐applied manure has been shown to be strongly correlated to dissolved P concentrations in runoff from agricultural soils. WEP tests that have a defined water‐to‐manure‐solids ratio and involve extraction times of 30 to 120 min provide the best prediction of dissolved P in runoff across a wide range of manures. Consistent measurement of manure WEP can be achieved with manure sample storage times of up to 22 days (4°C), acidified extract holding times of 18 days, and solid separation by either centrifugation or paper filtration. Reproducibility of WEP tests is comparable to that of other common manure tests (e.g., total P), as verified by within‐laboratory and inter laboratory evaluations. A survey of 140 livestock manures revealed significant differences in mean WEP among different livestock manures, with swine greater than poultry (turkey, broiler and layer chickens) and dairy cattle greater than beef cattle. Such results support the use of WEP‐based coefficients to modify the source component of the P index.

Development of a North American proficiency testing program for soil and plant analysis

Abstract A proposal for developing a unified proficiency testing program for soil and plant analysis laboratories in the North American region is presented. The proposed North American Proficiency Testing Program (NAPT) will be based on the quarterly submission to participating laboratories of six soil and/or three plant materials for chemical analysis using reference methods of analysis described in the four Regional Soil Work Group publications of NEC‐67, NCR‐13, SERA‐6, and WCC‐103 and methods outlined in Methods Manual for Forest Soil and Plant Analysis, Forestry Canada. Participating laboratories would complete sample analyses for all or any of the specified analytes and provide results to the NAPT program coordinator for statistical evaluation. Upon completion of the quarterly analysis each laboratory will be provided an evaluation of their individual performance on each of the methods listed. Annually the program will provide a report to each participant of the performance of the individual laborat...

Summary of Mehlich-3 P Data from Home-Lawn Soil Tests in Pennsylvania

InDISCRIMINATE USE of P-containing fertilizer on runof-prone turfgrass sites is thought to contribute to the contamination of ground and surface water (Soldat and Petrovic, 2008). Consequently, several states have enacted laws restricting the use of P fertilizers, and others are considering similar legislation. A bill restricting P and N fertilizer on turfgrass was recently introduced in Pennsylvania, and implications of the proposed legislation are currently being discussed with stakeholders. Although soil testing is primarily performed to assess nutrient status in crop and turfgrass systems, some researchers have used soil-test summaries to examine trends in nutrient management practices and the status of soil P in cropland and lawns at the regional scale (Sims, 2000). Soldat and Petrovic (2008) stated that little published data on trends in soil P concentrations exist for turfgrass sites, and such information would be beneicial to validate predictions made for lawns and other turf areas. he objective of this study was to determine soil-test P concentrations in Pennsylvania home lawns based on unsolicited soil samples submitted to Penn State’s Agricultural Analytical Services Laboratory (AASL). Data from Pennsylvania home-lawn soil samples submitted to AASL between 1 Jan. 2004 and 31 Dec. 2009 were assembled into a spread sheet and summarized. Samples were submitted by homeowners and professional lawn fertilizer applicators via test kits distributed from county extension oices in Pennsylvania. he distribution of test kits was on a request basis, and no attempt was made to solicit soil samples from homeowners and professional applicators for this study. Instructions for collecting soil samples are included in the kits and call for a sampling depth of 5.1 to 7.6 mm, 12 or more cores per sample from each sampling site, and discarding all grass and thatch from cores. All soil samples were processed and analyzed at AASL according to methods listed by Wolf and Beegle (1995). Phosphorus was extracted from soil samples using Mehlich-3 Published in Applied Turfgrass Science DOI 10.2134/ATS-2014-0048-BR