DOI: 10.15482/usda.adc/28267592.v1
title: Correlation and Calibration of Soil-Test Phosphorus Concentrations from Different Soil Depths with Soybean Yield

description: <b>Correlation and Calibration of Soil-Test Phosphorus Concentrations from Different Soil Depths with Soybean Yield</b>Md. Rasel Parvej*, Josh Copes, Syam Dodla, Peters Egbedi, Brenda Tubana, David Moseley, and Md. Moklasur Rahman*Corresponding Author: mrparvej@missouri.edu and parvejmr@gmail.comDivision of Plant Science & Technology and School of Natural Resources, University of Missouri, Columbia, MOSoybean [<i>Glycine max </i>(L.) Merr.] yield response to phosphorus (P) fertilization under different soil-test P levels was studied across 61 sites in Louisiana from 2020 to 2023. The main objective was to gather robust data for developing fertilizer-P recommendations for soybean production in Louisiana. These trials covered the major soybean-producing parishes in Louisiana that included 12 on-farm trials in producers’ fields (Avoyelles, 1; Concordia, 2; East Carroll, 2; Franklin, 3; Madison, 1; and Tensas, 3) and 49 research station trials from 6 different research stations of Louisiana State University Agricultural Center (Ben Hur Research Station in Baton Rouge, 4; Dean Lee Research Station in Alexandria, 8; Macon Ridge Research Station in Winnsboro, 20; Northeast Research Station in St. Joseph, 11; Red River Research Station in Bossier City, 5; and Sweet Potato Research Station in Chase, 1). The soil texture varied from sandy loam to clay, with 39 sites classified as sandy to silt loam and 22 as silty clay loam to clay.Each trial was designed as a randomized complete block with 4 to 5 replications and 3 to 5 fertilizer-P rate treatments (0, 20, 39, 59, and 78 kg P ha<sup>-1</sup>). In 2020 for site 1 to 14, the fertilizer-P rates applied were 0, 15, 29, 44, and 59 kg P ha<sup>-1</sup>. The experiment plots measured 3.9 to 4.1 m wide by 10.7 m long, with four crop rows. The seedbeds/crop rows at each site were spaced 96 to 102 cm apart, except for sites 17 and 18, which had 76 cm spacing. A detailed description of each research site, including the year, city, NOAA weather station, soil map unit, soil series, soil texture, and row spacing, is provided in the dataset.A composite soil sample, consisting of 6 to 14 cores, depending on soil depth, was collected from the control plot (0 kg P ha⁻¹) of each replication at four different soil depths: 0-10 cm, 0-15 cm, 0-20 cm, and 0-30 cm, before any fertilizers were applied. Soil sample at 0-10 cm, 0-15 cm, 0-20 cm, and 0-30 cm depth consisted of 14, 10, 8, and 6 soil cores, respectively. In 2020 (sites 1-14), samples were taken only from the 0-15 cm and 15-30 cm depths, and the soil test nutrient concentrations at the 0-30 cm depth were calculated by averaging the soil test values from the 0-15 cm and 15-30 cm depths. In 2023, soil samples from sites 55 and 58-61 were collected only from the 0-15 cm depth.Soil samples were collected using an AMS soil probe with a 2.2 cm diameter from the top of the middle two seed beds. Each sample was then dried in a forced air dryer at approximately 45°C for 5 days, ground to pass through a 2 mm sieve, and sent to Waters Agricultural Laboratories in Vicksburg, MS for analysis. The analyses included Mehlich-3 routine nutrient content (Helmke and Sparks, 1996), organic matter (Schulte and Hopkins, 1996), soil pH (Sikora and Kissel, 2014), estimated cation exchange capacity (ECEC, Maguire and Heckendorn, 2015), and percent base saturation. All soil properties for each depth at every experimental site are included in the dataset.Triple super phosphate (0-46-0; 200 g P kg<sup>-1</sup>) was used for the fertilizer-P treatments and broadcast on top of the seedbed of each plot at or before soybean planting or at soybean emergence. A soybean cultivar from mid to late maturity group IV, with a seeding rate of 297,000 to 346,000 seeds ha⁻¹, was planted on conventionally tilled beds following corn (<i>Zea mays</i> L.) at most sites. Exceptions included sites 2, 6, 7, and 12-14, which followed cotton (<i>Gossypium hirsutum</i> L.), and site 8, which followed sweet potato [<i>Ipomoea batata</i>s (L.) Lam.]. Planting dates ranged from early April to mid-June.All sites were furrow irrigated except for sites 1, 5, 16-18, 21, 23-24, 32-42, and 58, which were rainfed. The soybean cultivar name, irrigation type, planting date, and seeding rate for each site are included in the dataset. Irrigation, fertility, and crop management followed the Louisiana State University Agricultural Center Extension recommendations (Padgett et al., 2024; Parvej, 2021, 2024; Stephenson et al., 2024; Villegas and Towles, 2023). Soybean was harvested with a small plot combine from the middle two yield rows at maturity (R8, according to Fehr and Caviness, 1977). Harvesting dates ranged from late August to late October. Seed yield was determined at a uniform moisture content of 13% (130 g kg<sup>-1</sup> H₂O).This comprehensive dataset and methodology provide a solid basis for understanding the P needs of soybean crops in varying soil conditions and can guide future P fertilizer recommendations in Louisiana.<br><br>