Corn Response to Potassium Rates during Three Cropping Years in North Carolina

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−1 in 2010 and 2012, and 0, 19, 37, and 93 kg ha−1 in 2014. Potassium rates were 0, 93, and 187 kg ha−1 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−1 in both years. For all trials, the K source was muriate of potash (500 g kg−1 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−1 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 (Zea mays 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−1 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 HNO3, 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−1. 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.

本数据集采集于2010、2012及2014年作物生长季，旨在明确美国北卡罗来纳州山麓（Piedmont）、沿海平原（Coastal Plain）和潮汐带（Tidewater）三个地貌区的三个长期定位试验中钾（K）的临界土壤测试值（critical soil test value, CSTV）。

山麓试验（PRS_K，35.698832, -80.619754）位于北卡罗来纳州罗文县索尔兹伯里的山麓研究站（Piedmont Research Station）。该试验始于1985年，试验地块面积0.22公顷，土壤为Hiwassee壤土（细质、高岭石型、热性红化强发育湿润老成土（fine, kaolinitic, thermic Rhodic Kanhapludults）），采用免耕管理，设置4个钾素施用量梯度。

沿海平原区的长期定位试验位于北卡罗来纳州贝尔蒂县莱温斯顿-伍兹维尔的花生带研究站（Peanut Belt Research Station）。该试验（PBRS_K，36.126891, -77.180694）始于1982年，地块面积0.53公顷，土壤为Goldsboro壤土（粉质壤质、硅质、亚活性、热性水稳强发育湿润老成土（Aquic Paleudults）），采用常规耕作管理，设置3个钾素施用量梯度。

潮汐带试验点（TRS_K，35.861238, -76.658075）位于北卡罗来纳州华盛顿县普利茅斯的潮汐带研究站（Tidewater Research Station）。该试验始于1966年，地块面积2.2公顷，土壤为Portsmouth壤土（粉质壤质覆盖砂质或砂质骨架、混合、半活性、热性典型暗沃湿润老成土（fine loamy over sandy or sandy-skeletal, mixed, semiactive, thermic Typic Umbraquults）），采用少耕管理，设置5个钾素施用量梯度。

上述三个长期定位试验的土壤管理详细信息可参见Crozier等人（2004）与Morales等人（2023）的研究成果。

山麓试验点（PRS_K）2010和2012年的钾素施用量分别为0、19、37、75 kg·ha⁻¹，2014年为0、19、37、93 kg·ha⁻¹。沿海平原试验点（PBRS_K）2010至2014年的钾素施用量为0、93、187 kg·ha⁻¹。潮汐带试验（TRS_K）仅在2012和2014年作物生长季开展，尽管原试验设置5个钾素梯度，但仅评估了0、14、28 kg·ha⁻¹三个施用量梯度。

所有试验的钾源均为氯化钾（muriate of potash，K₂O含量500 g·kg⁻¹）。每个作物生长季，除钾素肥料外，所有小区均施用统一用量的磷（P），磷源为三重过磷酸钙（有效磷含量201 g·kg⁻¹）。磷、钾肥均在播种时撒施，未翻耕入土。

所有试验均采用随机完全区组设计。2010、2012及2014年作物生长季均种植玉米（Zea mays L.）。试验遵循标准农艺管理措施，包括除草剂、杀虫剂及杀菌剂的施用。山麓、沿海平原、潮汐带试验的总氮施用量（播种肥加追肥）分别为181、202、209 kg·ha⁻¹。

每年在玉米抽雄期，采集各试验点0–15 cm深度的土壤样品。样品送至北卡罗来纳州农业与消费者服务部（North Carolina Department of Agriculture & Consumer Services, NCDA&CS）土壤测试实验室。土壤钾采用Mehlich-3浸提法（Mehlich-3 extraction procedure，Mehlich, 1984a）提取，并用电感耦合等离子体光学发射光谱法（inductively coupled plasma optical emission spectroscopy, ICP-OES）进行分析。

在玉米R1/R2生育期，从每个小区的5株植株上采集穗位叶作为组织样品。玉米组织样品送至NCDA&CS植物/废弃物/介质/溶液检测部门，经硝酸湿法消解后，用电感耦合等离子体光学发射光谱法（ICP-OES）测定全钾含量。

通过收获每个小区的玉米果穗手动获取玉米产量数据。果穗脱粒后，将籽粒产量校正至155 g·kg⁻¹的标准商品含水率。

参考文献
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.