Comparison of four extractants used in soil phosphorus and potassium testing for two soils in a corn-wheat-soybean rotation in Tennessee receiving various amounts of P and K fertilizer

<p dir="ltr">The soils used in this study are from University of Tennessee (UT)’s Research and Education Center at Milan (35.9, -88.73333) and UT’s Highland Rim Research and Education Center at Springfield (36.466667, -86.816667). The soil at Milan is a moderately well-drained Grenada silt loam (fine-silty, mixed, active, thermic Oxyaquic Fraglossudalfs) and the soil at Springfield is a well-drained Mountview silt loam (fine-silty, siliceous, semiactive, thermic Oxyaquic Paleudults).</p><p dir="ltr"><br></p><p dir="ltr">These soil samples are from field experiments initiated in 2009. There were two separate fertilizer rate trials at each location, one for P and one for K, and each was implemented in a corn-winter wheat-soybean rotation. Phosphorus trials received five P fertilizer rates (0, 29, 59, 88, and 118 kg P ha–1 yr–1) and an annual maintenance rate of 149 kg K ha–1 yr–1. The K trials received five K fertilizer rates (0, 47, 93, 139, and 186 kg K ha–1 yr–1) and an annual maintenance rate of 79 kg P ha–1 yr–1. Nitrogen fertilizer was applied in both trials according to University of Tennessee’s recommendations for corn and wheat. No synthetic N was applied for soybean. Sources of N, P, and K were ammonium nitrate, triple superphosphate, and muriate of potash, respectively. Fertilizers were broadcast between mid-December and early March. Nitrogen was applied at planting in April for corn and between mid-February and mid-March for wheat. The treatments were arranged in a Latin Square Design (five treatments with five replications) in the corn–winter wheat–soybean rotation. Plots were 4.6 by 9.1 m with a 1.5-m alley between them. No-tillage management was followed at both locations throughout the trial.</p><p dir="ltr"><br></p><p dir="ltr">Soil samples were taken at the end of each crop year, from mid-December to as late as the end of February. The year associated with each soil value refers to the following or new crop year and should reflect the extractable P and K present before additional P and K fertilizer are applied for that new crop year (Savoy, 2013). Six, 0 to 15 cm depth soil cores (2.5 cm diameter) were randomly collected from each plot and composited. All soil samples were air-dried and ground to pass through a 2-mm sieve for analysis at the UT Soil, Plant and Pest Center (SPPC) in Nashville, TN. Mehlich-1 extraction (Mehlich, 1953) was also conducted at SPPC followed by determination of extractable P and K using Inductively coupled plasma optical emission spectroscopy (5300 DV ICP-OES, Perkin-Elmer, Waltham, MA). The remaining samples were transported to UT-Knoxville’s Department of Biosystems Engineering and Soil Science, where extractable P and K based on Mehlich-3 extraction (Zhang et al., 2014), Lancaster extraction (Oldham 2014), and Haney H3A extraction were conducted. The H3A extractant was prepared by combining 1.1 g malic acid, 0.7 g citric acid, and 0.45 g oxalic acid in 2 liters of water (personal communication with Richard Haney). Soil extraction was done by adding 40 ml of H3A to 4 g of soil, shaking for 10 minutes at 200 rpm, and filtering the extractant through 8 micron filter paper (Whatman 2V) into 50 ml plastic tubes. Inductively coupled plasma optical emission spectroscopy (5300 DV ICP-OES, Perkin-Elmer, Waltham, MA) was used for all analyses. </p><p dir="ltr"><br></p><p dir="ltr">It is to be noted that similar data is reported for wheat and soybeans in 2015 because soil sampling was done only once during this double-cropping season.</p><p dir="ltr"><br></p><p dir="ltr">The creation of this dataset was funded through University of Tennessee startup funds for the Jagadamma laboratory. The University of Tennessee is a land grant institution that receives NIFA funding through the USDA.</p><p dir="ltr">References:</p><p dir="ltr">Zhang, H., D.H. Hardy, R. Mylavarapu, and J.J. Wang. (2014). Mehlich-3. In: F.J. Sikora and K.P. Moore, editors, Soil test methods from the southeastern United States. Southern Coop. Ser. Bull. 419. Chapter 4.3. Clemson Univ. <a href="https://aesl.ces.uga.edu/sera6/PUB/MethodsManualFinalSERA6.pdf" target="_blank">https://aesl.ces.uga.edu/sera6/PUB/MethodsManualFinalSERA6.pdf</a></p><p dir="ltr">Oldham, J.L. (2014). Lancaster. In: F.J. Sikora and K.P. Moore, editors, Soil test methods from the southeastern United States. Southern Coop. Ser. Bull. 419. Chapter 4.4. Clemson Univ. <a href="https://aesl.ces.uga.edu/sera6/PUB/MethodsManualFinalSERA6.pdf" target="_blank">https://aesl.ces.uga.edu/sera6/PUB/MethodsManualFinalSERA6.pdf</a></p><p dir="ltr">Mehlich, A. (1953). Determination of P, Ca, Mg, K, Na and NH4 by North Carolina soil testing laboratories. University of North Carolina, Raleigh, NC. <a href="https://www.ncagr.gov/agronomi/pdffiles/mehlich53.pdf" target="_blank">https://www.ncagr.gov/agronomi/pdffiles/mehlich53.pdf</a></p><p dir="ltr">Savoy, H.J. (2013). Procedures used by state soil testing laboratories in the southern region of the United States. Southern Cooperative Series Bulletin 409. Clemson Experiment Station. <a href="https://aesl.ces.uga.edu/sera6/PUB/409June2013CUPDATE.pdf" target="_blank">https://aesl.ces.uga.edu/sera6/PUB/409June2013CUPDATE.pdf</a></p><p dir="ltr">Resources in this dataset:</p><ul><li>Resource Title: Jagadamma and Savoy 2020 Data.File Name: Jagadamma and Savoy 2020 Data 7.13.20.xlsx</li></ul><p dir="ltr"><br></p>