Phosphorus and Potassium Fertilizer Rate Verification for a Corn–Wheat–Soybean Rotation System in Tennessee

Abstract

Soil test-based fertilizer recommendations are necessary for profitable farming without adversely affecting the environment. The University of Tennessee (UT) stopped recommending P and K fertilizers in 2008 for soils with high Mehlich-1 P and K levels because they were unprofitable. However, commercial laboratories tend to recommend higher fertilizer rates than UT, despite equivalent soil test results. To address this discrepancy, field trials were conducted from 2009 to 2015 for a corn (Zea mays L.)wheat (Triticum aestivum L.)-soybean [Glycine max (L.) Merr.] rotation on low-to medium-testing soils at UT's Research and Education Centers at Milan and Springfield. Our specific objectives were to (i) evaluate yield responses to P and K rates; (ii) determine critical fertilizer rates, critical soil test P (STP), and soil test K (STK) levels, and critical grain P and K removals for maximum productivity; and (iii) examine the response of STP and STK levels to fertilizer P and K rates. We evaluated five rates of P (0-118 kg ha-1) and K (0-186 kg ha-1) fertilizers. Since 2013, significant yield responses to P and K fertilization were frequent, except no response to K was seen at Milan during the entire study period. Application of >59 kg ha-1 P resulted in high soil P levels over time at both locations but the highest K rate (186 kg ha-1) brought soils from a low to only a medium level. Critical fertilizer rates and soil test levels corroborated UT's current recommendations for maximum yield.

Agroecosystem management responses to Haney soil health test in the southeastern United States

“…Despite a few random responses of H3A-and Mehlich-1-extractable nutrients to managements, in this study Mehlich-1 showed notably lower measurement variability than H3A (Supplemental Table S1). Regardless, the content of nutrients extracted by both H3A and Mehlich-1 solutions were in accordance with other studies conducted in the region (Bansal et al, 2020;Chu et al, 2019;Singh, Savoy, Yin, Schneider, & Jagadamma, 2019;Zhou, Yin, & Verbree, 2014).…”

“…Mehlich‐1 and Mehlich‐3 solutions are commonly used for extracting nutrients from the soil, based on which fertilizer recommendations are calculated (Savoy, 2013). In Tennessee, where the current study was conducted, Mehlich‐1 is the recommended extractant for nutrient analysis (Bansal et al., 2020; Savoy & Joines, 2009; Singh et al., 2019). Switching to H3A in place of Mehlich‐1 and Mehlich‐3 to comply with HSHT will require extensive calibration and validation research in the region.…”

Long‐term influence of phosphorus fertilization on organic carbon and nitrogen in soil aggregates under no‐till corn–wheat–soybean rotations

“…Lower R 2 values and lack of significant positive correlation between SOC and crop productivity were also reported in studies by Dijkstra and Cheng (2007), Singh et al. (2019a), van Groenigen et al. (2006).…”

“…The categories of soil test P levels (Mehlich‐1) for Tennessee soils are: low (0 to 9 mg kg −1 ), medium (9.5 to 15 mg kg −1 ), high (15.5 to 59.5 mg kg −1 ), and very high (≥ 60 mg kg −1 ) (Duncan, Savoy, & Joines, 2015, Savoy & Joines, 2009). Soil samples were collected each year after the harvest of the crop but before applying fertilizers (Savoy, 2013) and Mehlich‐1 extractable soil P levels were evaluated in response to five P treatments (Table 2) (Singh et al., 2019a). At both sites, P application rates of 29 kg ha −1 and > 59 kg ha −1 maintained soil test P in medium and high category respectively (Duncan et al., 2015; Savoy & Joines, 2009; Singh et al., 2019a).…”

“…Soil samples were collected each year after the harvest of the crop but before applying fertilizers (Savoy, 2013) and Mehlich‐1 extractable soil P levels were evaluated in response to five P treatments (Table 2) (Singh et al., 2019a). At both sites, P application rates of 29 kg ha −1 and > 59 kg ha −1 maintained soil test P in medium and high category respectively (Duncan et al., 2015; Savoy & Joines, 2009; Singh et al., 2019a). Soil test P levels in the control treatment declined from medium to low category at Milan.…”