DOI: 10.15482/usda.adc/25035980
title: <b>Corn Response to Potassium Rates during Three Cropping Years in North Carolina</b>

description: This dataset was collected during the 2010, 2012, and 2014 cropping years aiming to determine the critical soil test value (CSTV) of potassium (K) in three long-term trials located in the Piedmont, Coastal Plain, and Tidewater physiographic regions of North Carolina, United States.
The Piedmont trial (PRS_K, 35.698832, -80.619754) is located at the Piedmont Research Station (Rowan County, Salisbury, NC). The trial started in 1985 in an area of 0.22 hectares on Hiwassee soil (fine, kaolinitic, thermic Rhodic Kanhapludults) managed under no-till with four rates of K. The long-term trial in the Coastal Plain region is at the Peanut Belt Research Station (Bertie County, Lewiston-Woodville, NC). The trial (PBRS_K, 36.126891, -77.180694) started in 1982 in an area of 0.53 hectares on Goldsboro soil (fine loamy, siliceous, subactive, thermic Aquic Paleudults) managed under conventional tillage with three rates of K. The Tidewater site (TRS_K, 35.861238, -76.658075) is at the Tidewater Research Station (Washington County, Plymouth, NC). The trial started in 1966 on 2.2 hectares of Portsmouth soil (fine loamy over sandy or sandy-skeletal, mixed, semiactive, thermic Typic Umbraquults) managed under minimum tillage, with five rates of K. Additional information about soil management realized on these long-term trials is described in Crozier et al. (2004) and Morales et al. (2023).
In the Piedmont site (PRS_K), K application rates were 0, 19, 37, and 75 kg ha<sup>−1</sup> in 2010 and 2012, and 0, 19, 37, and 93 kg ha<sup>−1</sup> in 2014. Potassium rates were 0, 93, and 187 kg ha<sup>−1</sup> at the Coastal Plain site (PBRS_K) from 2010 to 2014. At the Tidewater trial (TRS_K), the study was conducted just in 2012 and 2014 cropping years. Even though the trial have five rates of K, just three rates were evaluated, 0, 14, and 28 kg ha<sup>−1</sup> in both years. For all trials, the K source was muriate of potash (500 g kg<sup>−1</sup> of K). In each cropping year, together with the K, all plots received a uniform rate of phosphorus (P) using triple superphosphate as a source (201 g kg<sup>−1 </sup>of P). Phosphorus and K were broadcasted at planting without incorporation into the soil. The experimental design for all trials is a randomized complete block design.
The trials were cultivated with corn (<em>Zea mays</em> L.) during the cropping years of 2010, 2012, and 2014. Standard agronomic management practices, including herbicide, insecticide, and fungicide applications, were followed. Total N rates (at planting plus side-dress) were 181, 202, and 209 kg ha<sup>−1</sup> for Piedmont, Coastal Plain, and Tidewater.
Soil samples at 0–15 cm depth were collected at the tassel growth stage from all sites each year. Samples were submitted to the Soil Testing Laboratory at the North Carolina Department of Agriculture & Consumer Services (NCDA&CS). Soil K was extracted by Mehlich-3 extraction procedure (Mehlich, 1984a) and analyzed using inductively coupled plasma optical emission spectroscopy (ICP-OES). Tissue samples were collected by sampling the ear leaf from five plants in each plot at the R1/R2 growth stage. Corn tissue samples were submitted to the NCDA&CS Plant/Waste/Media/Solution Section. The tissue plant was submitted to wet digestion with HNO<sub>3</sub>, and the total K concentrations were analyzed for ICP-OES. Corn yield data were obtained manually by harvesting corn ears from each plot. The corn ears were shelled, and grain yields were adjusted to market standard moisture of 155 g kg<sup>−1</sup>.
REFERENCES
Crozier, C. R., Walls, B., Hardy, D. H., & Barnes, J. S. (2004). Response of cotton to P and K soil fertility gradients in North Carolina. Journal of Cotton Science, 8, 130–141.
Mehlich, A. (1984). Mehlich 3 soil test extractant: A modification of Mehlich 2 extractant. Communications in Soil Science and Plant Analysis, 15, 1409–1416. https://doi.org/10.1080/00103628409367568.
Morales, N. A., Gatiboni, L., Osmond, D., Vann, R., Kuleszka, S., Crozier, C., & Hardy, D. (2023). Critical soil test values of phosphorus and potassium for soybean and corn in three long-term trials in North Carolina. Soil Science Society of America Journal, 87, 278–290. https://doi.org/10.1002/saj2.20491.