Nutrient Uptake of Maize Affected by Nitrogen and Potassium Fertility in a Humid Subtropical Environment

Nitrogen (N) and potassium (K) fertility management of maize (Zea mays L.) in the humid subtropical Mississippi Delta may differ from a temperate climate because of its use in rotation with cotton (Gossypium hirsutum L.), soil temperatures rarely falling to 0°C, and heavy winter rains that facilitate nutrient losses. An experiment to determine the [N] (concentration=[ ]), phosphorus [P], [K], calcium [Ca], magnesium [Mg], iron [Fe], manganese [Mn], zinc [Zn], and copper [Cu] and their total contents plant −1 of maize grown in rotation with cotton, using N fertility levels of (134, 179, 224, 269, and 314 kg N ha −1 ) in combination with K fertility levels of (0, 45, 90, and 134 kg K ha −1 ) was conducted in 2000 and 2001 at Tribbett, MS. Ear leaves, immature ears, and husks collected at growth stage R2 and grain and stover collected 21 days after R6 were dried, weighed, and analyzed for nutrient concentration. Plots were also harvested for yield, kernel weight, grain bulk density, and harvest index (HI). Increased [N] values of about 1.3 mg g −1 occurred in all organs except the stover between 134 and 314 kg N ha −1 N fertility. Stover [N] increased approximately 3.0 mg g −1 within the same N fertility range. Total N content of ear leaves, grain, and stover increased by about 11.0, 550.0, and 730.0 mg plant −1 , respectively, with N fertility increased from 134 to 314 kg N ha −1 . Yields, kernel weights, grain bulk densities, and harvest indices also increased with added N fertility. Several micronutrient concentrations and contents increased as N fertility increased. Increased K fertility had only limited influence on concentrations of most nutrient elements. The nutrient contents of most elements in the stover increased with added K fertility compared with plots that received no supplemental K fertilizer. These data showed between 139 and 265 kg N ha −1 was permanently removed by grain harvest and suggest that N fertility recommendations for the Mississippi Delta may be low for maize yield goals above 10 Mg ha −1 . Added K fertilizer has minimal benefit to maize when soil test levels are adequate but are important to succeeding cotton crops where K uptake during fruiting can exceed the soil's ability to release K for uptake.